Tips, Suggestions, Advise For Using Macro Extension Tubes

[Soocom1]

Zeiss has a nice write up on this very issue:

https://lenspire.zeiss.com/photo/app/uploads/2018/04/Article-Bokeh-2010-EN.pdf

4. Smaller film format with the same lens

If we remove a lens from an old analogue camera and attach it to a digital camera of the same system that has a somewhat smaller APS-C sensor, then there is a "crop factor". We do not talk about an extension of the focal length, it doesn’t exist in this case. After all, the lens does not know how much of its image circle we are capturing with our sensor. The size of the object field is reduced by the crop factor while the object-side light cones remain the same, as long as we use the same lens and do not change the aperture setting. That is why the points of the light cones may not be located so far from the focal plane if we want to maintain the same ratio of diagonal to circle of confusion. Reducing the size of the film format therefore reduces the depth of field by the crop factor.

5. Different film formats with the same object field

If we select the suitable focal length to ensure that we always display the same field with different film formats, then things go just the other way round: reducing the size of the sensor format increases the depth of field, and enlarging the sensor format reduces the depth of field, as long as we always use the same aperture setting. That is because a smaller sensor format displays the same object field with an accordingly shorter focal length. If the same f-number is used, then the entrance pupil is reduced by the crop factor and the light cones are narrower. For the same reason, medium format photographs show a significantly smaller depth of field with the usual apertures, even though the absolute diameter of the imageside circles of confusion is larger, usually 0.05 mm as opposed to 0.03 mm in 35 mm format. If the medium format lens is adapted to a 35 mm camera, then of course we have to calculate with the 0.03 mm of the smaller format. The acceptable diameter of the circle of confusion is therefore not a characteristic of the lens but rather the sensor format. A feature of the lenses is only the smallest possible circle of confusion, and this arises from the correction of the lens aberrations. At first glance we therefore observe a paradoxical characteristic whereby large formats have a smaller object-side depth of field and simultaneously a larger imageside depth of focus with the same apertures and object fields. This is also reflected in the mechanical tolerances of cameras: Large-format cameras can be built with carpenter precision, and the camera module in a mobile phone requires µm (micrometer) precision. Those are the extremes, but in SLR photography we can already see the difference between APS-C and full-frame format with regard to the requirements for focusing accuracy. It appears to be a confusing paradox at first glance, but of course it has a very simple explanation. We just photographed object fields of the same size with different sizes of image formats. If the acceptable blurriness is supposed to be the same with these different cameras, it means that the ratio of the object field diagonal and the "object-side circle of confusion" should be the same. The object-side light cones travelling from a point behind the focal plane, for example, should therefore be the same for all compared cameras. If the images have different format sizes, however, the imaging scale is different. Under these conditions, the image-side circles of confusion must therefore increase along with the scale factor. The object-side light cones can only be the same if all entrance pupils are of the same size, however. But because object fields of the same size mean longer focal lengths for larger image formats, the f-numbers must be different

 

[Soocom1]

Now. the point being is that the physical size of the aperture (forget sensor size etc.) the actual physical size of the aperture on a MF v. 35mm is DIFFERENT because the MF lens is longer overall.
thus the f stop calculation comes up with a diff. number.

As a result, the actual amount of light is higher in the MF on 35mm at the same setting because the aperture size is diff.
Inverse square law dictates however that the distance of the macro extension lowers the light value inverse to the distance.

However: The light volume is still higher (albiet not much) with the MF lens attached.

 

[smoke665]

your results significantly softer than this

I already dumped the test images but I don't think they were significantly softer. Maybe my expectations exceed reality. LOL

 

[Derrel]

try using a fresh dollar bill taped to a wall as your test target for macro equipment---lots of fine lines, easy to focus on, "crisper" than a coin, and plenty large enough to reveal a lot of potential shooter errors, or equipment deficiencies. Using flash eliminates many potential problems

 

[adamhiram]

Maybe my expectations exceed reality. LOL

In the original spirit of this post, now I'm curious about some additional advice for getting sharper macro images with extension tubes. Besides the shot of the penny above, I took some additional test shots of the same subject with multiple lenses at different distances and different stacked extension tubes, but did not see significantly sharper results. I like Derrel's suggestion of using a flat dollar bill rather than a coin, and may try again when I have some time.

Some other variables I experimented with:

• Changed the lighting to multiple speed lights to be able to use a faster shutter speed, lower ISO, smaller aperture (camera shake from long exposure or from SLR mirror?)
• Removed any protective filters with no noticeable difference in sharpness
• Used a shorter extension for slightly less magnification, but more reasonable focusing distance
• Used a different lens that stopped down to f/32, but with results that didn't look much different (and probably had more diffraction)

 

[Soocom1]

I had posted this picture on another thread a few days ago:

The set up:

Canon 5D, manfrotto tripod, full three extensions (misc. brand tubes), Minolta MD-EOS 1.5x adapter (with the glass) and Promaster 80-200mm MD lens.


The distance shot was approximately 18 inches.

 

[smoke665]

I switched around with different combos tubes/lenses and never found a significant increase in sharpness. By comparison, this was shot last year with my 35mm Ltd, macro. ISO 100, f/10, 1/125.

And another, the vase in this image is 1 3/4" tall. Also shot at ISO 100, f/10, 1/125. Neither this one or the one above are extreme crops, I was working up close, don't remember the exact distance, but the MFD on the 35 is 12", so it was over that. Nor are these stacked.

And an extreme crop of the stems, note the tiny hairs visible

I never got this sharp of focus with the extension tubes, and the non-macro lenses.

 

[Derrel]

Maybe my expectations exceed reality. LOL

In the original spirit of this post, now I'm curious about some additional advice for getting sharper macro images with extension tubes. Besides the shot of the penny above, I took some additional test shots of the same subject with multiple lenses at different distances and different stacked extension tubes, but did not see significantly sharper results. I like Derrel's suggestion of using a flat dollar bill rather than a coin, and may try again when I have some time.

Some other variables I experimented with:

• Changed the lighting to multiple speed lights to be able to use a faster shutter speed, lower ISO, smaller aperture (camera shake from long exposure or from SLR mirror?)
• Removed any protective filters with no noticeable difference in sharpness
• Used a shorter extension for slightly less magnification, but more reasonable focusing distance
• Used a different lens that stopped down to f/32, but with results that didn't look much different (and probably had more diffraction)

On-screen the Lincoln cent is probably 15x to 20x bigger than in real life!
f/32 will almost assuredly cause softening due to diffraction.

 

[Derrel]

In many macro situations, not close-up situations, but real life-sized macro situations, often depth of field is 1 or 2 millimeter in distance...

hence my suggestion to use a flattened, fresh dollar bill, taped to a wall, as the test target.

 

[Dean_Gretsch]

I just shot both these handheld. I do not own a reliable rail system. My old, worn out original tripod has one, but is not worth digging it out of the basement, lol. All the other tripods I own do not have a rail, so anytime I shoot with tubes, I will just take several shots and hopefully get something decent enough to share. These were shot with my Lensbaby Velvet 56, which is f/1.6 and manual focus only. I was shooting manual with auto ISO and these are SOOC to show the magnification. We have very cloudy conditions and these are both with the little natural light we still have. The histogram showed shadows were barely clipped with the tube. Everything was great in histogram without the tube.

1/2000 sec. Camera ( sl1 ) chose 4000ISO

With 31mm tube. 1/2000 sec. Camera ( sl1 again ) chose ISO 6400

 

[Derrel]

As with anything new, sometimes it takes a while to get the hang of it, and sometimes a person just does stuff that's physically impossible, not knowing what it is that he does not know. I got my first extension tubes around 1981. I bought an inexpensive set at a street festival called Turkeyrama (turkey days) in McMinnville Oregon. Last of the extension tubes I bought was a Kenco AF set around 2002.

Something that I found out around 10 years ago was that some of the older 1980s era Nikon manual focus zoom lenses were designed with a macro function, which is invariably marked in orange, and such lenses as the 70 to 300 and the old 100 to 300 f/5.6 were designed with a 62 mm specially made two-element close-up lens in mind. That two element close-up lens is known as an achromatic doublet.other examples of this are the canon 250D and the canon 500D, and also several lenses sold by Raynox.

A few years ago there was a group of people who got fantastic results with the Raynox close-up lenses and smaller digicams.

 

[Derrel]

These magnifying lenses are much better thab cheap single element plus diopter filters. These are technically called lenses even though they are screw-in devices like most filters are. I have mentioned this several times on TPF for several years: the Nikon 100 to 300 mm f/5.6 AIS zoom lens with the Nikon 6T reverse mounted on the front of that lens with a simple and inexpensive filter reversing ring offers exceptionally high quality close-ups, and I mean flat field, and aberration free, and really,really good performance. This lens was never very popular, but it was designed with the Nikon 6T in mind. Some of Nikons better telephoto zoom lenses of the 1980s were designed to work with a Nikon 6T close-up lens. The Nikon 5T is a 52 mm diameter accessory, while the larger 6T is 62 mm thread diameter.

I heard about this strange combination in Bjorn Rotslett's "subjective Nikkor lens evaluations" page on the web. He is a Nikon lens expert, and one of the formost nature and macro photographers of his generation

The advantage of using a rather long lens such as the 100-300 mm or the 75 -300 mm is that with the right lens design, using a close-up filter attachment, there is no extension and therefore no loss of light through the diaphragm.

 

[Derrel]

Screw-innclosep lenses, such as those made by Nikon back in the olden days, and the current offerings by Canon and by Raynox have been given a bad name by piece of crap three filter sets, which are commonly called plus diopter sets. These cheaply-made and inexpensive magnifying filters are often sold used in pawnshops, and bring about five dollars for a used set of three. These usually have the strength marked on the rim of the filter and
are often sold as +1,+2, and +3 diopters. On the other hand the two element achromatic doublets offer really good performance, and they magnify the image, and help to eliminate chromatic aberration, hence why they are called achromatic. Depending on where the purchase is made, I would expect to pay between $45 and $120 for a high-quality example from one of these three manufacturers.

With the 135 mm and an extension tube added, you state that your minimum focusing distance is around 24 inches. If you were to add a Canon 500D,your image size on-film or on-sensor would be made larger, which has the effect of "being closer"

 

[smoke665]

On-screen the Lincoln cent is probably 15x to 20x bigger than in real life!
f/32 will almost assuredly cause softening due to diffraction.

I haven't had a chance to really explore using the tubes, but one thing I'm finding is the ability to focus with the manual rings is an issue. With the rings attached I'm limited to focusing in Live View. When I magnify the screen any adjustment to the lens creates a jittery image on the screen making exact focus on a narrow DOF difficult. As Adam suggested earlier using a focus rail or moving the subject might be a better method of getting sharp focus.

The other issue is the lens itself, the 35 ltd macro, is razor sharp, while the 135 seems to be just a tad soft. I'm wondering if that difference is also magnified by the use of extension tubes? Haven't had a chance to try it yet but I have a FA 50mm 1.4, that's also extremely sharp with a nice bokeh. The 50 and the 135 both have a magnification factor of .15x.

For about the price of a meal at McDonald's I got the tubes, so no biggy if they don't work. My original thought was if they did, to buy a more expensive set with full communication capabilities, but frankly after initial results, that may not happen. For not much more I can get the D FA 100mm f2.8 w/macro, that like the 35, has a MFD of 12", is extremely sharp, has great bokeh and doubles as an addition to my portrait primes.

More testing/experimenting is definitely required.

 

[adamhiram]

With the rings attached I'm limited to focusing in Live View. When I magnify the screen any adjustment to the lens creates a jittery image on the screen making exact focus on a narrow DOF difficult.

This was exactly my problem - with a DoF measured in millimeters or less, any movement of the camera/lens when touching the focus ring seemed like an exercise in futility. I opted to move the subject, stacking pieces of cardstock to get focus as close as possible, but that still required repositioning the subject over and over again.

I am interested in any recommendations for focusing rails. Based on my own research, everything is either terrible or $300+, neither of which are ideal. I'd love to find something "good enough" to play around with - perhaps the Neewer/Flashpoint rails, or Manfrotto's 454 positioning plate?