Nikon Series E lenses

[deepfriedl]

I recently bought a few Nikon Series E Lenses to use on my D3300. Specifically, I bought the 50mm f/1.8, the 28mm f/2.8, and the 70-210mm telephoto lens ( I think it's an f/4). I probably spent $100 all together, and I'm enjoying finding out what they good for.

One interesting thing I've found is that the focus doesn't seem to have the "range" that my kit lenses have. I can focus with much better clarity at a longer distance for a large image with my kit lenses than with the Series E lenses. The Series E lenses sort of max out at ∞ where I would still be able to adjust sharper focus with my kit lenses. Am I right to assume that this is because the Series E lenses were designed for a 35mm film camera and that Nikon expected that the largest those film shots would be blown up is 8x10?

Before anyone asks why I would use the Series E 70-210 f/4 when I have a Nikkor AF-S DX 55-200mm f/4-5.6G ED VR II, my girlfriend and I both use D3300's, but I bought the kit that also includes the Nikkor, and I like to lend it to her and use the Series E lens when we shoot wildlife.

 

[480sparky]

..........The Series E lenses sort of max out at ∞ .........

OK, so why would you ever need to focus beyond ∞?

 

[deepfriedl]

I probably didn't say that correctly. I'm a bit new at this. Say I have my 50mm f/1.8 pointed to a distant mountain side.I focus and find that it's sharpest at ∞. I then mount the standard kit lens, a Nikkor AF-S DX 18-55mm f/3.5-5.6G VR II, adjust the focal length to 50mm and focus. ∞ is further out on the Nikkor than the the Series E lens, and the sharpest focus seems to be beyond ∞ on the Series E lens, suggesting that the Nikkor has some greater capability for a sharp distant image.

edit: this only seems to matter because I'm shooting 6000x4000 images, btw. At whatever 8x10 would be, the difference is probably negligible, which is why I posted the question regarding blowing up 35mm film images when using those lenses on the old EM cameras.

 

[480sparky]

The markings on the lens barrel are really only estimations, not precision measurements. What is important is that the subject you wish to be in focus is actually in focus, regardless of what the lens barrel says.

 

[Derrel]

Those series E lenses have what is called "a hard Infinity stop"...crank the ring all the way, and the lens STOPS, at Infinity. Many AF lenses focus "beyond Infinity"....I know, right....Buzz Lightyear and all, but i;'s true...many AF lenses today lack a hard Infinity stop, and can focus "beyond" Infinity...which can lead to the foreground being rendered slightly out of focus, even at longer distances, like say 200 to 500 feet...and which necessitates very meticulous, careful focusing in situations like astrophotography, a type of shooting scenario in which the USER of the camera must determine when the lens if properly focused on Infinity--typically by using Live View, magnified.

Almost every Nikkor ED glass lens focuses beyond Infinity. ALL of the "big glass" super-telephotos from Nikon focus "beyond Infinity". So does the 135 f/2 Defocus Control lens.

The Series E 70-210 was a pretty decent zoom in its day!

 

[Tim Tucker]

I probably didn't say that correctly. I'm a bit new at this. Say I have my 50mm f/1.8 pointed to a distant mountain side.I focus and find that it's sharpest at ∞. I then mount the standard kit lens, a Nikkor AF-S DX 18-55mm f/3.5-5.6G VR II, adjust the focal length to 50mm and focus. ∞ is further out on the Nikkor than the the Series E lens, and the sharpest focus seems to be beyond ∞ on the Series E lens, suggesting that the Nikkor has some greater capability for a sharp distant image.

edit: this only seems to matter because I'm shooting 6000x4000 images, btw. At whatever 8x10 would be, the difference is probably negligible, which is why I posted the question regarding blowing up 35mm film images when using those lenses on the old EM cameras.

As 480sparky says, those markings aren't accurate.

Infinity is a theoretical distance and where the light hitting the lens from the subject is perfectly parallel. In practice you will find that the light from a tree leaf at 10 miles is as close to parallel as to make no practical difference, it will certainly have less of an effect on focus than the distortions through the atmosphere, so there's no advantage in designing an MF lens that even focusses at infinity. Allowing for manufacturing tolerance to ensure good focus at infinity the hard stops will be calibrated for slightly before infinity. You will not squeeze more IQ from the lens by changing this.

This is not really an issue as you can't achieve sharp focus on a 10 mile distance leaf with a standard camera lens, and you could even miss your focus on the moon by over a hundred thousand miles and not see the difference.

When viewing the images from the two lenses are you sure you're just measuring the focus and not seeing a difference in acutance due to lens coatings?

 

[astroNikon]

..........The Series E lenses sort of max out at ∞ .........

OK, so why would you ever need to focus beyond ∞?

You've heard the saying before ... "To Infinity ... and BEYOND !!"

 

[480sparky]

..........The Series E lenses sort of max out at ∞ .........

OK, so why would you ever need to focus beyond ∞?

You've heard the saying before ... "To Infinity ... and BEYOND !!"

So what would you record/see if you focused beyond infinity? Would you see back in time? Would you see something outside our universe, like another universe? Would you see a fence?

 

[MartinCrabtree]

At f1.8 vs f3.5 the details will be sharper. If you can preview depth of field stop the 50 f1.8 down to f4 and see if that clears it up for you. Focusing is performed at maximum aperture hence the difference.

 

[fmw]

The series E lenses were a budget line designed for amateur use. They were pretty good optically but not quite as rugged as the regular Nikkors. Most were not quite as forcefully corrected as their regular counterparts either. Think simplicity. But understand that some truly great Nikkors were relatively simple in design. The classic 105 f2.5 Nikkor was very well corrected and sharp as a tack with only 5 elements. It was one of the best Nikkors of all time. I have one so old that I took it to Nikon to have it and other lenses adapted for AI when I bought my F3. I still have it and use it when I need superior image quality.

 

[cgw]

The series E lenses were a budget line designed for amateur use. They were pretty good optically but not quite as rugged as the regular Nikkors. Most were not quite as forcefully corrected as their regular counterparts either. Think simplicity. But understand that some truly great Nikkors were relatively simple in design. The classic 105 f2.5 Nikkor was very well corrected and sharp as a tack with only 5 elements. It was one of the best Nikkors of all time. I have one so old that I took it to Nikon to have it and other lenses adapted for AI when I bought my F3. I still have it and use it when I need superior image quality.

Own or shoot any E series lenses? Otherwise, this is just the usual blow about the E series. Nikon brought them out to recapture market share lost to F-mount Tamron/Tokina/Kiron glass. Quality? They were tough enough for the largely non-pro market Nikon sold into--and still does. The 75-150/3.5 zoom? Killer. The 100/2.8? Gave nothing away to the larger, heavier, pricier 105/2.5.

 

[jcdeboever]

For 100 bucks, he has some very useful glass that should serve him well.

Sent from my XT1254 using Tapatalk

 

[Tim Tucker]

The series E lenses were a budget line designed for amateur use. They were pretty good optically but not quite as rugged as the regular Nikkors. Most were not quite as forcefully corrected as their regular counterparts either. Think simplicity. But understand that some truly great Nikkors were relatively simple in design. The classic 105 f2.5 Nikkor was very well corrected and sharp as a tack with only 5 elements. It was one of the best Nikkors of all time. I have one so old that I took it to Nikon to have it and other lenses adapted for AI when I bought my F3. I still have it and use it when I need superior image quality.

I would have to disagree on a couple of small points.

As far as MF lenses that are really classic and worth having the list of Nikkors is actually quite small, (I only own and shoot MF Nikkors). The list of useful E series lenses is not that much smaller. The 50/1.8 has the same optics as the 50/1.8D bar the coatings.

I bought my (second hand) Gauss design PC 105/2.5 when I was 18 and still use it today, I also have an earlier (1966) Sonnar version. Yes they are sharp, the Gauss being slightly better at close focus. They are great lenses and I'll never part with mine, but according to Nikon they were in fact deliberately under-corrected, especially the Sonnar:

NIKKOR - The Thousand and One Nights: Tale 5: - Best-selling mid-range telescopic lens - AI Nikkor 105mm F2.5 By Haruo Sato

 

[Derrel]

So what would you record/see if you focused beyond infinity? Would you see back in time? Would you see something outside our universe, like another universe? Would you see a fence?

Do you really NOT know or understand the idea of "focusing beyond an Infinity marking" on a lens?

Why is it possible to focus beyond infinity with some lenses? | Nikon Knowledgebase
Why is it possible to focus beyond infinity with some lenses?

Answer ID 18780|Published 12/06/2013 01:12 PM|Updated 12/06/2013 01:12 PM
. When focusing manually on some lenses you can focus beyond the infinity point. When set to this position, it results in the blurring of the image. Why is it possible to focus beyond the infinity point when infinity should be the maximum setting necessary to achieve focus?

A. The reason for this is that in extremely hot or cold conditions the effective focal length of the lens may change due to the effect of the temperature on elements in the lens, which causes expansion or contraction compared to optical performance at regular temperatures. Depending on the construction of the lens elements, some lenses will be affected more than others. To compensate for this, the option to focus with the lens beyond the infinity focus position is available on some lenses.

-----there's an answer fom Nikon's website...huh...
******

Who Killed Infinity Focus?
For decades, the Canon FD and EF lenses have featured a variable infinity setting. Canon has two reasons for this:

1. Thermal expansion
2. Allowances for infrared photography

Canon is compensating for thermal expansion in its optics, not the lens body. Optical glass and crystal materials, such as fluorite, are known to expand and contract with ambient temperature changes. These changes are not seen with the naked eye, but can cause refraction of the lens surface and, therefore, change the infinity distance. This is more of a factor in longer focal lengths but, as Canon points out, many of today's wide-angle zooms are simply inverted telephoto designs and they can be affected by temperature changes.



Have you ever wondered why Canon telephoto lenses are white? Well, when the company introduced its FC 600mm f/4.5 SSC lens in 1976, designers painted the lens barrel white to minimize thermal expansion of the fluorite lens. Nowadays, it is more of a marketing scheme than anything, but thermal compensation for infinity focus started Canon’s trademark white lens feature!

When it comes to IR photography, the longer wavelengths of IR light come into focus at a point farther than that for visible light. Due to this and certain industrial and military applications utilizing Canon lenses, the variable infinity range allows the user to maintain sharp focus, regardless of the lens's use.


FUJI
The only Fujifilm lenses in the current Fujifilm lineup featuring focus-distance markings are the Fujifilm XF 14mm f/2.8 R and the Fujifilm XF 23mm f/1.4 R lenses. Both barrels feature an ∞ mark, but the user can turn the focus ring beyond it. Interestingly, on these lenses, by turning the focus ring manually, you are not physically moving the lenses inside the lens body—you are manually sending electronic instructions to the autofocus motors inside the lens, which are then changing the lens focus; there is no clutch system that disengages the autofocus system. Therefore, on these lenses, it is not necessary to have a hard-stop at the infinity point, as the lens/camera autofocus system components are handling the focus responsibilities.

Fujifilm says that because, even when "manually" focusing the lens, you are using the AF system, and the camera can figure out when the lens is focused at infinity by using a hybrid contrast and phase-detection autofocus sensor. Therefore, no special lens calibration or hard stop is needed. The virtual variable range of infinity on Fujifilm lenses allows for temperature expansion.

HASSELBLAD
Some Hasselblad lenses feature an "over-focus" position, allowing the user to turn the lens past the ∞ mark. However, this distance may, in fact, be so minuscule that you cannot visually see it on the lens barrel marking. Hasselblad does this to ensure sharp focus when the lens is subject to thermal expansion.

Interestingly, Hasselblad currently features a special lens for aerial photography that is fixed at an infinity focus position and the company has been developing cameras for NASA, including the cameras and Zeiss lenses used on the moon, that are subject to a 300-degree C temperature swing between sun and shade—possibly the greatest thermal challenge in the photography world—with designated infinity settings.

LEICA
Leica's lenses have always been known for their mechanical precision and great tactile feel when it comes to focus, zoom, and aperture adjustments. Today, the Leica M lenses still feature a hard stop at the ∞ mark. However, some of the company’s R-system and all of its S-system lenses allow for movement past the infinity setting. Leica claims this is for accommodating thermal action, which is more critical as the size of the digital format grows. This movement also helps compensate for a physical change in focal length when teleconverters or adapters are added to a lens setup. The Leica M lenses, with their compact size and limited focal-length ranges, do not need this additional movement.

MAMIYA
On Mamiya lenses, users will find a hard stop at the right edge of the ∞ mark. This hard stop sits on the "far side" of a calibrated infinity position and indicates the far point of a variable infinity range. Mamiya lenses feature this variable range for the purposes of supporting its "Open Platform" philosophy as the company is designing camera bodies and lenses that accommodate digital backs from other manufacturers, some more than a decade old. Mamiya builds to exacting standards, but wants its camera system to accommodate a wide variety of backs that may not have been built to Mamiya's tolerances. For autofocus work, the 645DF+ features a system that calibrates with the autofocus of a specific lens, and matches the focal plane seen by the AF module to that of the sensor, to provide precision focusing with different backs.

Mamiya states that, within the specified working temperature range of its camera systems, there should be no differences in focusing due to thermal expansion when operating inside that range.

Mamiya's wide-angle lenses are required to produce a large image circle for medium format cameras. The company adds that most wide-angle lenses will feature some field curvature, and the ability to focus beyond infinity helps compensate for that. This is even more evident in large format photography, where many helical focusing mechanisms have user-adjustable scales.

NIKON
Many of today's Nikon lenses feature focus rings that move beyond both the ∞ mark and the close-focus point because the Nikkor AF-S autofocus system features a differential cam that allows for both autofocus and autofocus with manual override. The "M/A" mode allows the photographer to manually turn the focus ring when the lens is in any autofocus mode, thus permitting manual-focus capabilities without having to change focus modes from auto to manual.

Older Nikkor AF lenses and some of the AF-S line, such as the AF-S DX 18-55mm, do not feature the M/A autofocus mode and users of those lenses will see hard stops at the ∞ mark and close-focus point (if the lens barrel has focus markings) very similar to the older, but still-in-production, Nikon manual-focus lenses.


OLYMPUS
The current Olympus line has three M.ZUIKO lenses with manual focus rings and focus markings. The M.ZUIKO 12-40mm f2.8 PRO, M.ZUIKO 12mm f2.0 PREMIUM, andM.ZUIKO 17mm f1.8 PREMIUM feature the ability for the photographer to turn the ring past the ∞ mark for three reasons:

1. For manual-focus photography
2. For the autofocus system
3. For the Image Stabilization system
4. For manual focus, the system allows the user to definitively confirm accurate focus when focusing on distant subjects using "Magnified Assist" or "Focus Peaking." For autofocus, this ability to turn past the ∞ mark is designed to allow the Olympus contrast-detection autofocus system to function. The autofocus system is designed to focus by moving just past the determined focus point and then back to the point to ensure accurate autofocus. Imagine if you may, how you might have focused a manual-focus lens, binoculars, or telescope by going back and forth between blurry, sharp, and blurry. The Olympus AF system does the same thing. Lastly, Olympus states that with the advent of both in-camera and in-lens image stabilization (IS), it became necessary to allow lens focusing past the infinity position, as the IS system moves either the sensor or lens group, which will then change the location of the infinity focus point.

Many legacy Olympus lenses do feature a hard stop at the ∞ mark. Those using older Olympus lenses may confirm the infinity focus accuracy using their digital EM-1's focus peaking feature.

PANASONIC
Panasonic lenses do not have a mechanical stop at the ∞ mark by design. The company admits that this may be frustrating to some photographers, but they have incorporated some high-tech methods to set their "G" series lenses to infinity focus:

1. Select the manual focus "MF" mode on the camera, and then turn the camera off. Turn the camera back on and it will automatically reset to the infinity focus point.
2. Using the rear LCD screen with the camera in "MF" mode, turn the focus ring on the lens until the red and white scales meet (see photo below) and you have precise infinity focus.

PENTAX
Grab a Pentax lens off the shelf at B&H and you will see that even the autofocus zoom lenses have a hard stop precisely at the ∞ mark. Unfortunately, I was unable to get information from their engineers; nevertheless, their owner's manuals tell a slightly different story:

From DA Interchangeable Lens Manual: “When focusing with manual focus or the Quick-Shift Focus System, the mechanism allows the focusing ring to rotate freely after it is set to the ∞ (infinity) or the minimum focus distance ends. However, do not attempt to rotate it any farther than these ends as this will result in decreased performance.”

From the Pentax-D FA Interchangeable Lens Manual: "Note: When focusing manually, do not turn the focusing ring all the way to infinity or to the minimum focusing distance."

From the smc Pentax-FA Interchangeable Lens Manual: "The telephoto lens's focusing ring stops turning at slightly past the ∞ infinity symbol. This is because, the point of focus changes depending on the temperature, and sometimes the focus is achieved beyond the ∞ symbol. Even when focusing at infinity, always look through the viewfinder to make sure the subject is in focus. When the lens is set for manual focus, the focusing ring can continue to turn even past the minimum focusing distance or infinity mark."

From the FA Interchangeable Lens Manual: "When the lens is set to the manual-focus position and the focusing ring is fully rotated to the right or left to manually focus the lens, it will keep rotating, as no stoppers are provided at the ∞ (infinity) or shortest-distance positions.
"The focusing ring of the telephoto lens stops slightly past the ∞ mark. This is because temperature change chases the focusing point to shift, making the lens focus on a point past the ∞ mark. Even when shooting at infinity, be sure the lens is in focus utilizing the focus indicator before releasing the shutter."

SAMSUNG
A relative newcomer to the interchangeable-lens camera arena, Samsung's lenses have focusing rings that turn past infinity and only one of their current line, the Samsung 85 f/1.4 ED SSA, features focusing marks on the lens. Their owner's manuals state that the zoom lenses are not parfocal and need focus adjustments after zooming in or out.

SAMYANG / ROKINON
Elite Brands sells manual-focus lenses under the Rokinon/Samyang branding. Their lenses feature a hard stop following a variable infinity region designated by an "L" marking on the lens or the ∞ mark by itself. These manual-focus lenses have a superb, classic, tactile feel. Being an aftermarket manufacturer, they are designing lenses that accommodate upwards of 10 different camera mounts and, because of the varying thicknesses of these mounts, need to allow users to utilize a variable infinity focus range to find precise focus. Precisely calibrating an infinity point for each variant of the lenses for each mount would be cost prohibitive.

SCHNEIDER
Schneider Optics features a very small line of manual-focus lenses for DSLR cameras. The company's classic PC-Super-Angulon lens features a hard stop at the ∞ mark, as do its newer PC-Tilt Shift lenses that come in different focal lengths and several different lens mounts. Schneider states that the PC-Tilt Shift line's infinity setting is built to a tolerance of ± 0.02 mm, so that the infinity focus will be sharp even with the lens aperture opened to its maximum. This precision extends to the focusing mechanism itself. Schneider finds that the thermal expansion of the lens can be accommodated for in the depth of field of the aperture setting, even at full aperture, and is not a factor affecting the lens's precise focus.

The company makes an extensive line of cinema lenses that feature a variable infinity range to accommodate thermal changes in the lens and for filter stacking. According to Schneider, it is not uncommon for motion picture cameras to have anywhere between two and five filters stacked on a lens. These filters may change the camera's magnification and, therefore, move the focus point―necessitating a variable infinity range.

Schneider also mentioned that the new, non-crystal glass used in optics is much more thermally and humidity stable than the older crystal "glass," and, this newer glass (sometimes referred to as low dispersion or ED glass) allows tighter manufacturing tolerances.

SIGMA
Some Sigma lenses feature hard stops at the ∞ mark, but their autofocus lenses with the ring-shaped Hyper Sonic Motors feature a "soft stop." The focus rings on these lenses have the ability to keep turning past both the ∞ mark and the close-focus point to protect the durability of the autofocus motor. According to the Sigma engineers in Japan, this allows the motor to slow to a stop instead of reaching the stopping point abruptly.

SONY
Sony's rapidly expanding lens line features several approaches to the infinity-focus conundrum. Many of its lenses are devoid of focus markings, and the manual focus rings spin freely with no stops at all. Several of the company’s lenses feature soft-stops and the "L" marks, denoting a variable-infinity range. The owner's manuals claim that the "infinity position provides for some adjustment to compensate for focus shift caused by a change in temperature," before recommending that focus is verified through the viewfinder or live view modes.

One of several lenses that features a hard stop at the ∞ mark is the Sony 135 f/2.8 STF lens that is unique in the Sony line—its only manual-focus lens. The lens features a classic focusing feel and sense of precision when the focus ring stops right at the ∞ mark.

From the Sony DT 50 f/1.8 SAM manual: "To shoot a subject at infinite distance in MF mode: The infinity position provides for some adjustment to compensate for focus shift caused by a change in temperature. To shoot a subject at infinite distance in MF mode, use the viewfinder and set focus.”

From the Sony DT 16-50mm f/2.8 SSM manual: "Shooting at infinity in MF: The focusing mechanism turns slightly past infinity to provide accurate focusing under various operating temperatures. Always confirm the image sharpness through the viewfinder of [sic] other viewing part, especially when the lens is focused near infinity."

From the Sony DT 11-18mm f/4.5-5.6 and 18-250mm f/3.5-6.3: "The focusing ring can be rotated slightly past the infinity to provide accurate focusing under various operating temperatures. Do not rotate the focusing ring all the way to the end when focusing manually, even at infinity. Look through the viewfinder and set the focus precisely."

TAMRON
All of Tamron's current zoom lenses and 90mm macro prime lens feature what they call "over infinity." This is designed into the lens to allow sharp focus at the variable infinity point, regardless of thermal expansion of the lens.

From a Tamron lens owner's manual: "The focusing ring rotates beyond the infinity position in order to properly focus to infinity under a variety of environmental conditions. When manually focusing, make sure the subject at infinity is sharp in the viewfinder."

TOKINA
Tokina says that, in theory, parfocal zoom lenses should be able to feature a hard stop at the ∞ mark, but the company allows its lenses to focus beyond the mark to accommodate thermal changes. The manufacturer states that even a relatively small temperature variation might cause the infinity focal point to move and, in certain situations, if a hard stop was installed, the lens may not be able to reach infinity focus.

From the Tokina 300mm f/6.3 MF Macro Manual: "Generally, a super-telephoto lens with a range of 300mm or more will have some allowance in the position of the infinitely [sic] symbol (∞). This is because the refractive index of light in air changes as the temperature in the mirror cylinder changes and the focus position may shift slightly as a result. Accordingly, be sure to adjust the focus carefully by checking the image on the finder screen, even when capturing a distant view, starry sky, or other very distant subject."

VOIGTLANDER
German manufacturer Voigtlander manufactures its infinity stops to high precision and spends a great deal of time manufacturing with metals and materials that combine to cancel out thermal expansion. Several Voigtlander lenses feature a hard stop at the ∞ mark and the MFT Nokton lenses have an "over infinity position."

ZEISS
Older Zeiss lenses for still photography feature a hard stop at the ∞ mark. Their new cinema lenses, the Master Prime, Ultra Prime, and Compact Zoom lenses will focus past infinity to provide an "extra margin of focus control." This same feature was incorporated into the new Zeiss Otus series of lenses. Zeiss states that its lenses are designed to account for thermal expansion and the variable-infinity range is not needed to compensate for changes in temperature.

Well, there you have it, directly from the sources. A combination of thermal expansion and allowances for autofocus motors seems to be the largest factor in the "softening" of the infinity focus. Thermal expansion has been around since the dawn of time, though, yet it seems to be a bigger concern to lens manufacturers now than in the past. Some makers, however, have taken measures to accommodate for thermal changes to their lenses.

I would like to thank the representatives and engineers from all of the above companies who took time out of their busy schedules to speak with me about their products. I hope you, our readers, find this information as fascinating as I have.

 

[480sparky]

So what would you record/see if you focused beyond infinity? Would you see back in time? Would you see something outside our universe, like another universe? Would you see a fence?

Do you really NOT know or understand the idea of "focusing beyond an Infinity marking" on a lens?

Why is it possible to focus beyond infinity with some lenses? | Nikon Knowledgebase
Why is it possible to focus beyond infinity with some lenses?

Answer ID 18780|Published 12/06/2013 01:12 PM|Updated 12/06/2013 01:12 PM
. When focusing manually on some lenses you can focus beyond the infinity point. When set to this position, it results in the blurring of the image. Why is it possible to focus beyond the infinity point when infinity should be the maximum setting necessary to achieve focus?

A. The reason for this is that in extremely hot or cold conditions the effective focal length of the lens may change due to the effect of the temperature on elements in the lens, which causes expansion or contraction compared to optical performance at regular temperatures. Depending on the construction of the lens elements, some lenses will be affected more than others. To compensate for this, the option to focus with the lens beyond the infinity focus position is available on some lenses.

-----there's an answer fom Nikon's website...huh...
******

Who Killed Infinity Focus?
For decades, the Canon FD and EF lenses have featured a variable infinity setting. Canon has two reasons for this:

1. Thermal expansion
2. Allowances for infrared photography

Canon is compensating for thermal expansion in its optics, not the lens body. Optical glass and crystal materials, such as fluorite, are known to expand and contract with ambient temperature changes. These changes are not seen with the naked eye, but can cause refraction of the lens surface and, therefore, change the infinity distance. This is more of a factor in longer focal lengths but, as Canon points out, many of today's wide-angle zooms are simply inverted telephoto designs and they can be affected by temperature changes.



Have you ever wondered why Canon telephoto lenses are white? Well, when the company introduced its FC 600mm f/4.5 SSC lens in 1976, designers painted the lens barrel white to minimize thermal expansion of the fluorite lens. Nowadays, it is more of a marketing scheme than anything, but thermal compensation for infinity focus started Canon’s trademark white lens feature!

When it comes to IR photography, the longer wavelengths of IR light come into focus at a point farther than that for visible light. Due to this and certain industrial and military applications utilizing Canon lenses, the variable infinity range allows the user to maintain sharp focus, regardless of the lens's use.


FUJI
The only Fujifilm lenses in the current Fujifilm lineup featuring focus-distance markings are the Fujifilm XF 14mm f/2.8 R and the Fujifilm XF 23mm f/1.4 R lenses. Both barrels feature an ∞ mark, but the user can turn the focus ring beyond it. Interestingly, on these lenses, by turning the focus ring manually, you are not physically moving the lenses inside the lens body—you are manually sending electronic instructions to the autofocus motors inside the lens, which are then changing the lens focus; there is no clutch system that disengages the autofocus system. Therefore, on these lenses, it is not necessary to have a hard-stop at the infinity point, as the lens/camera autofocus system components are handling the focus responsibilities.

Fujifilm says that because, even when "manually" focusing the lens, you are using the AF system, and the camera can figure out when the lens is focused at infinity by using a hybrid contrast and phase-detection autofocus sensor. Therefore, no special lens calibration or hard stop is needed. The virtual variable range of infinity on Fujifilm lenses allows for temperature expansion.

HASSELBLAD
Some Hasselblad lenses feature an "over-focus" position, allowing the user to turn the lens past the ∞ mark. However, this distance may, in fact, be so minuscule that you cannot visually see it on the lens barrel marking. Hasselblad does this to ensure sharp focus when the lens is subject to thermal expansion.

Interestingly, Hasselblad currently features a special lens for aerial photography that is fixed at an infinity focus position and the company has been developing cameras for NASA, including the cameras and Zeiss lenses used on the moon, that are subject to a 300-degree C temperature swing between sun and shade—possibly the greatest thermal challenge in the photography world—with designated infinity settings.

LEICA
Leica's lenses have always been known for their mechanical precision and great tactile feel when it comes to focus, zoom, and aperture adjustments. Today, the Leica M lenses still feature a hard stop at the ∞ mark. However, some of the company’s R-system and all of its S-system lenses allow for movement past the infinity setting. Leica claims this is for accommodating thermal action, which is more critical as the size of the digital format grows. This movement also helps compensate for a physical change in focal length when teleconverters or adapters are added to a lens setup. The Leica M lenses, with their compact size and limited focal-length ranges, do not need this additional movement.

MAMIYA
On Mamiya lenses, users will find a hard stop at the right edge of the ∞ mark. This hard stop sits on the "far side" of a calibrated infinity position and indicates the far point of a variable infinity range. Mamiya lenses feature this variable range for the purposes of supporting its "Open Platform" philosophy as the company is designing camera bodies and lenses that accommodate digital backs from other manufacturers, some more than a decade old. Mamiya builds to exacting standards, but wants its camera system to accommodate a wide variety of backs that may not have been built to Mamiya's tolerances. For autofocus work, the 645DF+ features a system that calibrates with the autofocus of a specific lens, and matches the focal plane seen by the AF module to that of the sensor, to provide precision focusing with different backs.

Mamiya states that, within the specified working temperature range of its camera systems, there should be no differences in focusing due to thermal expansion when operating inside that range.

Mamiya's wide-angle lenses are required to produce a large image circle for medium format cameras. The company adds that most wide-angle lenses will feature some field curvature, and the ability to focus beyond infinity helps compensate for that. This is even more evident in large format photography, where many helical focusing mechanisms have user-adjustable scales.

NIKON
Many of today's Nikon lenses feature focus rings that move beyond both the ∞ mark and the close-focus point because the Nikkor AF-S autofocus system features a differential cam that allows for both autofocus and autofocus with manual override. The "M/A" mode allows the photographer to manually turn the focus ring when the lens is in any autofocus mode, thus permitting manual-focus capabilities without having to change focus modes from auto to manual.

Older Nikkor AF lenses and some of the AF-S line, such as the AF-S DX 18-55mm, do not feature the M/A autofocus mode and users of those lenses will see hard stops at the ∞ mark and close-focus point (if the lens barrel has focus markings) very similar to the older, but still-in-production, Nikon manual-focus lenses.


OLYMPUS
The current Olympus line has three M.ZUIKO lenses with manual focus rings and focus markings. The M.ZUIKO 12-40mm f2.8 PRO, M.ZUIKO 12mm f2.0 PREMIUM, andM.ZUIKO 17mm f1.8 PREMIUM feature the ability for the photographer to turn the ring past the ∞ mark for three reasons:

1. For manual-focus photography
2. For the autofocus system
3. For the Image Stabilization system
4. For manual focus, the system allows the user to definitively confirm accurate focus when focusing on distant subjects using "Magnified Assist" or "Focus Peaking." For autofocus, this ability to turn past the ∞ mark is designed to allow the Olympus contrast-detection autofocus system to function. The autofocus system is designed to focus by moving just past the determined focus point and then back to the point to ensure accurate autofocus. Imagine if you may, how you might have focused a manual-focus lens, binoculars, or telescope by going back and forth between blurry, sharp, and blurry. The Olympus AF system does the same thing. Lastly, Olympus states that with the advent of both in-camera and in-lens image stabilization (IS), it became necessary to allow lens focusing past the infinity position, as the IS system moves either the sensor or lens group, which will then change the location of the infinity focus point.

Many legacy Olympus lenses do feature a hard stop at the ∞ mark. Those using older Olympus lenses may confirm the infinity focus accuracy using their digital EM-1's focus peaking feature.

PANASONIC
Panasonic lenses do not have a mechanical stop at the ∞ mark by design. The company admits that this may be frustrating to some photographers, but they have incorporated some high-tech methods to set their "G" series lenses to infinity focus:

1. Select the manual focus "MF" mode on the camera, and then turn the camera off. Turn the camera back on and it will automatically reset to the infinity focus point.
2. Using the rear LCD screen with the camera in "MF" mode, turn the focus ring on the lens until the red and white scales meet (see photo below) and you have precise infinity focus.

PENTAX
Grab a Pentax lens off the shelf at B&H and you will see that even the autofocus zoom lenses have a hard stop precisely at the ∞ mark. Unfortunately, I was unable to get information from their engineers; nevertheless, their owner's manuals tell a slightly different story:

From DA Interchangeable Lens Manual: “When focusing with manual focus or the Quick-Shift Focus System, the mechanism allows the focusing ring to rotate freely after it is set to the ∞ (infinity) or the minimum focus distance ends. However, do not attempt to rotate it any farther than these ends as this will result in decreased performance.”

From the Pentax-D FA Interchangeable Lens Manual: "Note: When focusing manually, do not turn the focusing ring all the way to infinity or to the minimum focusing distance."

From the smc Pentax-FA Interchangeable Lens Manual: "The telephoto lens's focusing ring stops turning at slightly past the ∞ infinity symbol. This is because, the point of focus changes depending on the temperature, and sometimes the focus is achieved beyond the ∞ symbol. Even when focusing at infinity, always look through the viewfinder to make sure the subject is in focus. When the lens is set for manual focus, the focusing ring can continue to turn even past the minimum focusing distance or infinity mark."

From the FA Interchangeable Lens Manual: "When the lens is set to the manual-focus position and the focusing ring is fully rotated to the right or left to manually focus the lens, it will keep rotating, as no stoppers are provided at the ∞ (infinity) or shortest-distance positions.
"The focusing ring of the telephoto lens stops slightly past the ∞ mark. This is because temperature change chases the focusing point to shift, making the lens focus on a point past the ∞ mark. Even when shooting at infinity, be sure the lens is in focus utilizing the focus indicator before releasing the shutter."

SAMSUNG
A relative newcomer to the interchangeable-lens camera arena, Samsung's lenses have focusing rings that turn past infinity and only one of their current line, the Samsung 85 f/1.4 ED SSA, features focusing marks on the lens. Their owner's manuals state that the zoom lenses are not parfocal and need focus adjustments after zooming in or out.

SAMYANG / ROKINON
Elite Brands sells manual-focus lenses under the Rokinon/Samyang branding. Their lenses feature a hard stop following a variable infinity region designated by an "L" marking on the lens or the ∞ mark by itself. These manual-focus lenses have a superb, classic, tactile feel. Being an aftermarket manufacturer, they are designing lenses that accommodate upwards of 10 different camera mounts and, because of the varying thicknesses of these mounts, need to allow users to utilize a variable infinity focus range to find precise focus. Precisely calibrating an infinity point for each variant of the lenses for each mount would be cost prohibitive.

SCHNEIDER
Schneider Optics features a very small line of manual-focus lenses for DSLR cameras. The company's classic PC-Super-Angulon lens features a hard stop at the ∞ mark, as do its newer PC-Tilt Shift lenses that come in different focal lengths and several different lens mounts. Schneider states that the PC-Tilt Shift line's infinity setting is built to a tolerance of ± 0.02 mm, so that the infinity focus will be sharp even with the lens aperture opened to its maximum. This precision extends to the focusing mechanism itself. Schneider finds that the thermal expansion of the lens can be accommodated for in the depth of field of the aperture setting, even at full aperture, and is not a factor affecting the lens's precise focus.

The company makes an extensive line of cinema lenses that feature a variable infinity range to accommodate thermal changes in the lens and for filter stacking. According to Schneider, it is not uncommon for motion picture cameras to have anywhere between two and five filters stacked on a lens. These filters may change the camera's magnification and, therefore, move the focus point―necessitating a variable infinity range.

Schneider also mentioned that the new, non-crystal glass used in optics is much more thermally and humidity stable than the older crystal "glass," and, this newer glass (sometimes referred to as low dispersion or ED glass) allows tighter manufacturing tolerances.

SIGMA
Some Sigma lenses feature hard stops at the ∞ mark, but their autofocus lenses with the ring-shaped Hyper Sonic Motors feature a "soft stop." The focus rings on these lenses have the ability to keep turning past both the ∞ mark and the close-focus point to protect the durability of the autofocus motor. According to the Sigma engineers in Japan, this allows the motor to slow to a stop instead of reaching the stopping point abruptly.

SONY
Sony's rapidly expanding lens line features several approaches to the infinity-focus conundrum. Many of its lenses are devoid of focus markings, and the manual focus rings spin freely with no stops at all. Several of the company’s lenses feature soft-stops and the "L" marks, denoting a variable-infinity range. The owner's manuals claim that the "infinity position provides for some adjustment to compensate for focus shift caused by a change in temperature," before recommending that focus is verified through the viewfinder or live view modes.

One of several lenses that features a hard stop at the ∞ mark is the Sony 135 f/2.8 STF lens that is unique in the Sony line—its only manual-focus lens. The lens features a classic focusing feel and sense of precision when the focus ring stops right at the ∞ mark.

From the Sony DT 50 f/1.8 SAM manual: "To shoot a subject at infinite distance in MF mode: The infinity position provides for some adjustment to compensate for focus shift caused by a change in temperature. To shoot a subject at infinite distance in MF mode, use the viewfinder and set focus.”

From the Sony DT 16-50mm f/2.8 SSM manual: "Shooting at infinity in MF: The focusing mechanism turns slightly past infinity to provide accurate focusing under various operating temperatures. Always confirm the image sharpness through the viewfinder of [sic] other viewing part, especially when the lens is focused near infinity."

From the Sony DT 11-18mm f/4.5-5.6 and 18-250mm f/3.5-6.3: "The focusing ring can be rotated slightly past the infinity to provide accurate focusing under various operating temperatures. Do not rotate the focusing ring all the way to the end when focusing manually, even at infinity. Look through the viewfinder and set the focus precisely."

TAMRON
All of Tamron's current zoom lenses and 90mm macro prime lens feature what they call "over infinity." This is designed into the lens to allow sharp focus at the variable infinity point, regardless of thermal expansion of the lens.

From a Tamron lens owner's manual: "The focusing ring rotates beyond the infinity position in order to properly focus to infinity under a variety of environmental conditions. When manually focusing, make sure the subject at infinity is sharp in the viewfinder."

TOKINA
Tokina says that, in theory, parfocal zoom lenses should be able to feature a hard stop at the ∞ mark, but the company allows its lenses to focus beyond the mark to accommodate thermal changes. The manufacturer states that even a relatively small temperature variation might cause the infinity focal point to move and, in certain situations, if a hard stop was installed, the lens may not be able to reach infinity focus.

From the Tokina 300mm f/6.3 MF Macro Manual: "Generally, a super-telephoto lens with a range of 300mm or more will have some allowance in the position of the infinitely [sic] symbol (∞). This is because the refractive index of light in air changes as the temperature in the mirror cylinder changes and the focus position may shift slightly as a result. Accordingly, be sure to adjust the focus carefully by checking the image on the finder screen, even when capturing a distant view, starry sky, or other very distant subject."

VOIGTLANDER
German manufacturer Voigtlander manufactures its infinity stops to high precision and spends a great deal of time manufacturing with metals and materials that combine to cancel out thermal expansion. Several Voigtlander lenses feature a hard stop at the ∞ mark and the MFT Nokton lenses have an "over infinity position."

ZEISS
Older Zeiss lenses for still photography feature a hard stop at the ∞ mark. Their new cinema lenses, the Master Prime, Ultra Prime, and Compact Zoom lenses will focus past infinity to provide an "extra margin of focus control." This same feature was incorporated into the new Zeiss Otus series of lenses. Zeiss states that its lenses are designed to account for thermal expansion and the variable-infinity range is not needed to compensate for changes in temperature.

Well, there you have it, directly from the sources. A combination of thermal expansion and allowances for autofocus motors seems to be the largest factor in the "softening" of the infinity focus. Thermal expansion has been around since the dawn of time, though, yet it seems to be a bigger concern to lens manufacturers now than in the past. Some makers, however, have taken measures to accommodate for thermal changes to their lenses.

I would like to thank the representatives and engineers from all of the above companies who took time out of their busy schedules to speak with me about their products. I hope you, our readers, find this information as fascinating as I have.

Do you really NOT know or understand the idea of sarcasm?