A Confusion with Lenses and Focal Length

[andytakeone]

So if a lens's focal length is defined by its distance to the camera's sensor, does that mean all lenses are identical and that the only difference is the length of the cylinder it is built into?

Of course I know this can't be true and that there are more complications than that. But what are those complications?

My guess would be that the curvature of each lens has to be adjusted depending on the lens's focal length. But if that's true, than that would mean that a 50mm lens adjusted so that it is 28mm away from the sensor does not make it a 28mm lens--which then diminishes the definition of focal length.

Can anyone help me with this confusion?
If you can extend this discussion to prime lenses and zoom lenses that would be the cherry on top.

 

[Braineack]

Wait till you read about telephoto

using tapatalk.

 

[480sparky]

One complication is that if you were to actually measure the distance between your camera flange and the sensor, you'd discover that there appears to be a minimum focal length available. This is due to the mirror movement within the camera, as well as the shutter between the mirror and sensor.

So optical designers employ a technique called 'retrofocus' to be able to put a 6mm lens that physically cannot be placed closer than 40mm from the sensor.

 

[snowbear]

The distance from the front of the lens to the sensor is for a simple lens. I'd wager a paycheck you don't have any simple lenses but compound lenses: those with multiple glass elements so the physical length is really much shorter than in the simple lens of the same focal length.

Enjoy.

 

[Jim Walczak]

This is just my own opinion, however I think snowbear hit the nail on the head there...when we're talking about focal length in terms of the back of the lens to the camera, we're not really taking about "focal length" in conventional terms. As snowbear said, most camera lenses (even kit lenses) use multiple elements in their design, so we're not talking about focal length in the same terms as we might with say, a telescope (and these days, even scopes usually use multiple elements...even my cheapy Simmons uses 2 elements in the objective). The only real consideration or exception here would be "macro photography", where you might use extension tubes between the lens and the camera sensor in order to get extreme close ups of very small subjects...say the eyes of an insect. That however is a different and rather specialized form of photography and not specifically relevant at this point.

The way to think about focal length in terms of photography is simply the distance of the camera/lens in regard to the subject. A 55mm lens for example, will be roughly equivalent to the field of view that most people see with the naked eye (always a nice place to start). In other words, using a 55mm lens, if you look thru the view finder at a given subject then pull the camera away from your eye, what you "see"...your subject...should appear as roughly the same distance away as you saw thru the view finder (give or take your own vision of course...some people are near sighted, some are far sighted, which changes that theory a bit). Shorter focal lengths, 28mm, 24mm, 18mm, 12mm, etc., will provide a progressively wider field of view (respectively) and your subject will appear further away from the camera...hence the term "wide angle". Conversely, a longer focal length, 100mm, 200mm, 300mm, etc., will magnify that field of view, making your subject appear closer than it actually is.

The significance is simply in being able to properly frame your subject with the camera. For example, let's say your interest is "wildlife" and you've spotted a lovely white tail deer across a field...we'll say 100 yards away (for the sake of easy, round numbers). That's the length of a football field, so say you're standing at one end of the field and the deer is at the other end....that deer is pretty far away from you. If you were to use a wide angle lens, let's say 18mm, then your "subject" - the deer, is likely to appear as little more than a tiny little spot in an image that could otherwise be mistaken as a landscape photo. By using a longer focal length...say 500mm, you can magnify the deer in your view finder so that you're taking a picture of the deer. Conversely, if you were to use that same 500mm lens to try and do a portrait of someone standing only 20 feet away from you, you'd likely end up with an extreme close up of the person's nose...you'd likely want to use something closer to a 50 to 100mm range for that (unless of course you happen to like noses, LOL).

On this issue alone, my advice would be to not worry about the "tech talk" as it pertains to the distance of the lens to the sensor (that is unless your intent is to start designing/building lenses) and just concern yourself with the relevance of focal length in terms of the distance to your subject.

Now regarding prime vs. zoom lenses, much of this is, for all intensive purposes, the same. Prime lenses also use multiple elements, so in terms of distance regarding the lens to the camera, it's pretty much irrelevant. Likewise, a 400mm prime will magnify your subject where a 12mm prime will make your subject appear further away. Focal length however is different in that a zoom gives you a range of focal lengths to work with. While typically not the greatest lens you can buy, let's consider an 18-200mm "super-zoom" as an example. The advantage of such a lens is that it gives you a very wide focal range to work with...at 18mm, you can stand on a beach and take lovely sunset pictures and with a twist of the lens, you can "zoom in" to 200mm and get a shot of the blue heron that may be down the beach from you...and you don't have to move your position to do this. That's why a lot of folks (myself included) consider these to be a good "walking around lens"...despite their flaws, they are very convenient to use. With primes on the other hand, you'd mount an 18mm lens, take the sunset shots, then take that lens off and mount a 200mm lens to get the shot of the heron...otherwise, you'd simply have to move MUCH closer to the heron to use that 18mm. In other words, in order to effectively cover the whole range of that 18-200mm zoom lens, you'd likely have to carry 4 or 5 additional lenses (or more) with you if all you have are prime.

The big consideration here is actually about image quality. Some people will argue that a prime lens will always produce a better image than a zoom lens will...and at one time, that was VERY true. With my 40 year old Canon 35mm for example, if you were to compare images shot with a 50mm prime and my old Sigma 28-70mm zoom, there would be no question AT ALL...the prime would produce a better image (regardless of brand). In the old days, zooms were prone to problems with image distortion, chromatic aberration and even a general lack of sharpness. They were good for -some- people, but for many, the advantage of a zoom usually wasn't worth the image degradation (although a great deal of that would depend on the person using the camera and their intent...4 x 6 snapshots with a zoom lens for example were usually fine). That said, the times they have a changed! Thru the use of computer design, modern manufacturing techniques and tremendous quality control efforts, most lens makers today (including 3rd party vendors such as Tamron and Sigma) can produce zoom lenses that are in fact quite comparable to primes. Even the so-called "kit lenses" today can provide a really great value considering their price...that cheapy Nikon 18-55mm I use so much is a FAR superior lens to my old Sigma 28-70 as far as image quality goes. Some people are REALLY stubborn about this, however the truth is that the better modern zooms really do a very good job, even when compared with primes.

Okies, not sure if that's what you were really looking for, but I hope it helps and gives you a bit of insight.

 

[astroNikon]

Lenses are engineered to provide an in-focus image to the sensor.
Each camera's sensor is a certain distance from the flange (where you attach the lens). ==> Flange focal distance - Wikipedia, the free encyclopedia

That provides the engineers a fixed model to develop their lens.
So multiple manufacturers can make lenses to do anything, at any size, width and tube length BUT it must provide a focused image at the sensor plan from the flange.

The competing factors are end user price, image quality & manufacturing costs.

After that, since a lens is made up of multiple elements, everything else can be different: The number of elements, the size of elements, the type of elements, element materials, the total tube height of the lens. New element design techniques are allowing lenses to be smaller and more compact ==> Another Nikon patent for a 300mm f/4 lens with diffractive optical element (DOE) | Nikon Rumors

As long as the engineered lens provides the in-focus image at the sensor it doesn't matter how long or short a particular lens is (look at pancake lenses as an example ==> Nikon 50mm f/1.8 Series E).

Here are Nikon's two 50mm lenses.
a Nikon 50mm/1.8 AF-D lens is approx 1.5 inches tall ==> Nikon 50mm f/1.8 D Review

whereas a Nikon 50mm/1.8 AF-S G lens is approx 2.1 inches tall ==> Nikon AF-S 50mm f/1.8 G

Compare those lens elements to a 18mm type lens, which uses much more curved elements to capture a larger width, or field of view. (scroll down a little to see the element design) ==> Nikon 18-35mm f/3.5-4.5 G Review

Of look at the size difference of the two 24mm lenses on the left of this picture ==> http://www.btobey.com/nikon/images/24mm-size-nikon.jpg

The lens objective is to provide an in-focus image to the image sensor.
as the above discussion of the Diffractive Optical lenses, the new 300/4 is shorter and lighter than the old 300/4 while providing a high quality image.

Thus, in reality the length of a lens and the "tube" really hasn't nothing to do with it's field of view/focal length as the engineering design is for a particular focal length (prime or zoom). The lens elements dictate it's field of view (focused image focal length). The wider angle lenses have much more curved elements in general and the longer ones have much flatter outer elements.

You "could" make a long 50mm (as long as a 300mm) but it may suffer from image quality and providing a dark image to the sensor - and who would buy such a thing compared to the small ones?

It's all in the design and whether the engineers use a certain mathematical model which will produce lenses of a certain length, elements/image quality and cost.

Now if you have a camera that does not have a lens then you don't have to worry so much about the distance from the "hole" to the film, such as pinhole cameras. you just have to worry about the exposure. ==> How does a pinhole camera work?

And you can use pinhole lenses on dslrs ==> http://www.amazon.com/Holga-299120-Pinhole-Nikon-Black/dp/B007TPXL46
==> How to use Holga Pinhole Lens on Nikon D7000 DSLR | Photography Forum


here's a good read => Camera lens - Wikipedia, the free encyclopedia

==> How Camera Lenses are Made - The Beat: A Blog by PremiumBeat

 

[480sparky]

...... A 55mm lens on a 35mm film camera or full-frame DSLR for example, will be roughly equivalent to the field of view that most people see with the naked eye ...........

FIFY.

FOV is not dictated by focal length alone.

 

[Jim Walczak]

...... A 55mm lens on a 35mm film camera or full-frame DSLR for example....

FIFY.

FOV is not dictated by focal length alone.

You're correct...obviously there's more to it than that. Since the OP seems to be a novice regarding this (indicated by "confusion with lenses and focal length"), I was merely trying to simply things for the benefit of the OP, rather than going on about some otherwise fairly irrelevant techno-babble at this point. Using my deer explanation at 100 yards for example - if you're looking thru an 18mm lens, you ARE going to see A LOT more in your FOV (field of view) than you would with a 500mm...that was the point I was trying to make regarding focal length. This is just my own opinion, but I believe this is far more important for a novice to understand rather than the specific nuances your comment would indicate, let alone specifics like the lens distance to the sensor.

I would also point out that I did NOT include the comment about "35mm or full frame" deliberately as I didn't wish to confuse the subject even further by introducing the concept of crop factors. In fact, regardless of FF or APS-C, the focal length is the same. The focal length itself does not change based on the crop factor of the camera sensor...a smaller sensor does NOT magnify the image, it just crops off more of the edge. 50mm is still 50mm either way.

Not trying to be rude - just clarifying my comments.

 

[Dave442]

One interesting note is that a Telephoto lens is by definition a lens where the physical length of the lens is shorter than the focal length of the lens.
A prime lens has one focal length when measured at infinity (the focal length can change on some lenses when going to the closer focusing distances - focus breathing). A zoom lens is a variable focal length lens. The zoom lens may include the telephoto optics and if it also covers the wide angle range it may also have a retrofocus set of optics.

I would suggest some books that cover this in much better detail and more correctly than I can put down here.
1) "Handbook of Optics" Volume 1 and 2 - all the basics and formulas.
2) "Applied photographic optics" - geared towards photographic lenses.
3) "Optical Systems Engineering"

 

[petrochemist]

The lenses focal length is NOT defined by its distance from the sensor.
It is an intrinsic property of the lens and is not affected by the cameras position.
(In fact it's actually a series of properties as focal length is dependent on the wavelength of light, but the difference across the visible spectrum is fairly marginal)
Focal length is actually defined by where parallel rays of light are brought to a point, or the point the rays appear to come from for divergent lenses.

With a simple lens, the lens is moved further away from the sensor to focus closer, some more complex lenses focus in the same way moving all the elements together. Others move just a few elements which will alter the focal length.

 

[andytakeone]

Wow, thanks for the comprehensive answers everyone.

Every post helped tremendously.

Main takeaway was that focal length isn't defined by the distance from the sensor, and as petrochemist said, it is defined by where parallel rays of light are brought to a point.
I don't completely understand where the measurement (mm) comes into play, but it's a good starting point for me.

 

[Jim Walczak]

I don't completely understand where the measurement (mm) comes into play, but it's a good starting point for me.

I'm sure someone will likely pop in here with the specifics, however personally, while I'm sure I've learned it a few times over the years...the specifics have never been anything worth remembering for me, LOL!!! Part of it I'm sure is just that I've been doing this for so long (over 40 years), that I can usually just glance at a subject/scene and (usually) know which lens I want to use. If I'm shooting critters for example, be it wildlife, animals at a zoo, or even dogs at a local dog park, I know I'm usually going to want a long lens...my 70-300mm works great for many situations, however I know I could certainly put a 400mm or even 500mm to VERY good use....the further away something is, the longer lens you will need. If I'm shooting landscapes (of cityscapes) I know I'm usually gonna want a wide angle (in fact I've been doing a fair bit of interior work here lately, so an ultra wide...something in the 12mm range, has made it onto my wish list). If I'm doing portraits (rare, but it happens), I usually prefer something in the 80 to 100mm range. If I'm working in low light situations, stage photography for example, I've found my 70-200mm f/2.8 to be a good compromise for many situations (although a really fast 50mm also has it's advantages)...you get the idea. I will experiment and play around with lenses sometimes, particularly if I have something new or unusual...I've recently picked up a couple of older manual lenses that I'll likely mess around with a bit to see what their strengths (and weaknesses) are, but again for myself that's more about using the lens and getting to know it, rather than much/any consideration regarding the mathematics of it.

Not sure if this helps or not, but something I had done (several times in fact) when I first started taking my photography work more seriously, was to take all my lenses to a given scene...say a landscape for example...and take several shots using each lens (at different apertures and in the case of zooms, using different focal lengths), then comparing the results of each lens afterwards (either on my computer or even with some prints) so I could see exactly how each lens would perform.

I would also add that...for myself at least...there's a common sense rule I follow as well; if you frame your subject in the viewfinder and it's not large enough for the composition, you either need to move closer to the subject or simply use a longer lens! LOL! Conversely, if you look thru the viewfinder and things appear too close/too large, you either need to move back or use a shorter lens. Not really that hard to figure out and doesn't require any terribly proficient math skills .

I'm sure there are folks out there who do find the nuances of the math quite useful, but personally I rely on the practical experience of working with my own gear. It's always a good idea to read and learn all you can and books, how to videos and forums such as this are great resources, however at the end of the day I'm a very firm believer in that "we learn by doing". Just take the lenses you have available and go shoot something that interests you...you'll get the idea pretty quick.

 

[soufiej]

"So if a lens's focal length is defined by its distance to the camera's sensor, does that mean all lenses are identical and that the only difference is the length of the cylinder it is built into?"




While not exactly your question, the latter half of your question, IMO, is the key issue you should be concerned with as a photographer.

Therefore, are all lenses "identical"?

The clearest answer is, of course, no, they are not identical. They are, however, very much more alike than ever before.

Leaving aside the issues of focus and handling, operation and features, today's lens makers have joined today's camera designers to create what is called a "lens profile".

Each camera body also has an ideal profile which describes its specified performance and corrects for individual instances of deviations from that standard. The camera also detects the lens being used (assuming it can be identified within the database) and makes internal corrections for that specific lens. In many ways, this ability to correct for known errors is what has made the single fixed lens "enthusiast's camera" genre so successful.

Within the digital circuitry of the camera are error correction circuits which make many adjustments to the digital image data file both prior to and after the storage of the data in the system's memory. In other words, during the recording process and the playback process. If you shoot and edit using RAW capture, you understand the data file is not complete even when it exits the camera's systems.

Since any modern circuitry has its +/- deviations from ideal which will be limited by the tolerances applied to the various components within the circuit, some cameras and some lenses require more or less correction to reach a comfortable standard. Filters are a part of this correction though each filter introduces yet another error in another value. To correct for aliasing errors for example, an anti-aliasing filter will introduce time and phase errors.

Good filters and good circuitry cost money and that is a good portion of what you are buying when you upgrade your equipment. Yet, how to build a good circuit or a good filter is subject to both subjective and objective debate. How to combine those discrete parts into one whole is an even more contentious subject.



Obviously, none of this existed in the days of analog gear. When you purchased an upgraded lens or camera body in 1978, you were mostly buying far great tolerances in the mechanical and optical operation - in other words, tighter control over increasingly smaller deviations - of each component in the chain. Among the many plus and minus, pro and con debates for digital circuitry handling analog data, the effort has most often been to make all things more alike. This reduces the cost to the average consumer. It also tends to homogenize all equipment into an acceptable middle ground of not terrible but also not great performance.

Just as you can now buy a digital audio player for well under $50 and a digital video system for about the same, many of those differences between the low end and the high end products in photography have diminished with de-sensitization and the lowered acuity of the listener/viewer. In other words, if you are not prioritizing those things which make up the differences in subjective quality, then all things are very much alike to the average consumer.

Today's smart phones turn out images that are often deemed "great" by the average consumer.



This same homogenization of quality exists in all digital photography. Putting aside the basic issues of, say, sensor size and lens "speed", high quality photos can be turned out by relatively inexpensive digital equipment.

Any image that is turned out in digital photography has been digitally "processed". The data has been manipulated by other digital circuits and the final result is the cumulative effect of the lens/camera quality plus the quality and versatility of the processing software plus the skills of the person doing the manipulation via software.



Those photographers using the Adobe software packages are well aware of lens correction profiles; Lightroom Lens Corrections Explained

The use of digital data and digital error correction systems can now minimize the real world differences between the low end and the high end of photographic equipment. The result is ultimately dependent on the processing power of the software and the person doing the processing. Though most such corrections are achieved by simply clicking on a box.



Does this make all lenses "identical"? No, but it does, IMO, make the differences between base line, low cost lenses and their far more costly cousins far less important to the average photographer than in the days of analog equipment.

 

[Jim Walczak]

Does this make all lenses "identical"? No, but it does, IMO, make the differences between base line, low cost lenses and their far more costly cousins far less important to the average photographer than in the days of analog equipment.

At the risk of hijacking this thread, while I will EASILY admit that lens manufacturing has come a long way in recent decades...better computer aided designs, better manufacturing techniques, much higher quality control standards, etc., over-all I think I have to disagree with this sentiment.

I think the truth of the matter is that throughout the 60's, 70's and 80's (and even earlier really), there was always a division in the masses regarding quality. For example, your comment says "Today's smart phones turn out images that are often deemed "great" by the average consumer", however was this not also true of the days when people used Polaroids, Kodak Instamatics and wow...even those old Kodak "disk" cameras? Likewise, compare 35mm to medium format...do we STILL not see this today in the difference between DSLR and say, a Phase One medium format digital back? Even in terms of 35mm alone, A LOT of people used to use 3rd party lenses...Tamron and Sigma have both been around for a long while, not to mention brands like K-Mart's "Focal" and other department store brands (Sears, Montgomery Wards, etc). A great many people used such brands back in the day and were just as happy as the "average photographer" is with such brands today.

Even in terms of processing, while the way we work has changed, having grown up doing dark room work in my earliest days, I can honestly say that what we do today in Photoshop...not really THAT different at all. Photoshop is easier, faster and less messy...no more squinting for endless hours under that red light bulb...but many of the processes are still the same. Burning, dodging, cropping, exposure/contrast adjustment, image retouching...ALL have long been excepted post processing practices. And for those who simply took their rolls of film into FotoMat (or other such labs), there was ALWAYS a degree of processing and corrections that took place...automatic exposure and contrast adjustments and such have been around a loooooooong time.

I also have to feel your comment left out one VERY important aspect regarding all of this; the photographer. Whether we're talking 35mm, DSLR, Polaroid, camera phone, Instamatic or even a Kodak "Brownie", it's the photographer who takes great images. As history has proven time and time again, it's just NOT about "the gear". You can have the most expensive body on the planet and a foot locker full of high dollar primes, but if you don't understand basic principles and concepts such as composition, the rest just doesn't matter at all. A good photographer on the other hand, can use very humble equipment and still create truly amazing images.

Likewise you said "It also tends to homogenize all equipment into an acceptable middle ground of not terrible but also not great performance"...again this is nothing new (or old) at all. For example, that $50 mp3 player you mention...while digital audio is certainly something of an improvement over the days of vinyl and 8-tracks, there's a reason why brands like Bose and Nakamichi cost considerably more than your average I-Pod player and why there are even brands out there that are even more expensive still (check out HigherFi's "Titan 2's" - $510,000!!!)...just as it was 40 years ago. That said, just as with 40 years ago, not everyone has a specific need to be a true audiophile...I won't speak for others, but I certainly have some very fond memories of the old 8-track player in my '73 Ford Galaxy! LOL!!! Photography or audio, you've always had high end equipment, low end and that ever abundant middle ground...seriously...you don't get too much more "homogenized" than Realistic! LOL!

Now there is one thing that HAS changed over the last 40 years or so...the internet. I think this could be the crux of the matter regarding our perception of amateur photography efforts today. Ok...I hate to admit it, but yea...I'm starting to get old. Thinking back to the 1970's, let's face it...unless you were a genuine professional, the only people who really got to see your work (as an amateur) were usually friends & family...maybe a few people at a local photography club or something. Seriously...how many of us shot countless rolls of film that would ultimately end up in the proverbial shoe box? Yea...sure...maybe you did an occasional enlargement of something "special"...a certain vacation or wedding picture or something, but even there, how many people really got see your work? Does that mean all such work was simply horrible? Hardly. I don't have any statistics to back this up, but I suspect there were A LOT of really great photographers back in the 60's, 70's and 80's (even before) who may have shot some truly INCREDIBLE images, who have simply gone as unsung heroes because those image have long since rotted away in the shoe box sitting in the back of the closet.

I guess there's probably something of a stereotype here that makes it easy for some people to think that photos from those decades were always just terrible unless taken by a pro. I suspect that many of us older folks today have some frightening memories of the slideshows "Uncle Bob" used to torture us with for hours on end - "This is Aunt Jane at Disneyland...this is Aunt Jane with Micky Mouse...this is Aunt Jane spilling her beer on Micky Mouse...that was my thumb in front of Micky Mouse as Aunt Jane was hugging him...". Yikes, I say...YIKES!!! That said however, I can look back through some old family photo albums...my family's trip to Hawaii back in '78 for example...and even though Dad was a LOUSY photographer, yea...there's actually some good, if not really great images in those albums. Certainly comparable to what people might shoot with camera phones these days.

So what's the difference? The internet. Again, back in the day few people outside of family and friends would get to see those vacation pictures. Today however, it just take a few mouse clicks to post those shots to Facebook, Pinterest or any number of (gasp) photo forums. In the 70's and 80's, my pictures may have been seen by maybe 10 or 20 people...today hundreds, if not thousands of people from all over the world can view a given person's work, amateur or pro alike. That said, I don't think that means that the work of your "avid enthusiasts" has really improved THAT much in the past 50 years...average photographers and enthusiasts have been around a LONG time. It simply means we get to see more....A LOT MORE of it today than we ever have before.

While I do understand the point you have tried to make, I think you have put an over-emphasis on the wrong issue. Are cameras & lenses today better, with the quality more consistent than they were 40 years ago? Sure...just as the technology of the 70's was better than what was available 40 years before that. Technology evolves...from the consumer side of the issue, I do believe that's a good thing. That said, I also have to believe that the distinction in quality between budget/entry level, mid range equipment and pro/high end gear is still quite significant to say the least, however I equally have to STRONGLY feel that's totally independent of the skills of the person using it.

My apologies to the OP for having hijacked the thread, but I truly felt compelled to throw my own $.02 worth in there.

 

[soufiej]

Jim, I do think you've missed my point.

First, the op's question had nothing to do with the photographer. I would think you'd find very few on this forum who would disagree with the sentiment the photographer creates the initial quality of the image with the equipment as secondary back up.

However, that has nothing to do with the op's question regarding lenses nor does it have anything really to do with my post. I didn't discuss the creation of the image because it had nothing to do with the op's question. I addressed only the software being applied to the digital data file both in-camera and in post production.

Strictly speaking, the photographer has no real world control over either. The photographer doesn't even need to be present for the latter to occur.




"Great photos" often come not from the technical merits of the image. As I have mentioned previously on this forum, I have a collection of pre-Castro Havana photos taken by my aunt using a simple Brownie Kodak. I am amazed at the images she captured.

It would indeed be a rarefied world if the only great photos we as a society favored were those which displayed no chromatic aberrations, distortions or vignetting. Most viewers simply are unaware of those issues, that they exist or that some few folks would point them out as limitations to the quality of a photo.

Most people today accept the ... uh, ... "emotional impact" of a photo as its greatest overall contribution to quality. In that respect, a photo of Aunt Emma blowing out her birthday candles with Uncle Bob's thumb in the frame can still qualify as memorable when it displays the unique personality of each subject. Not much has changed there in the last few decades.

Equally, Cap'n Crunch still sells by the palette load.




Those technical issues of the lens which create its unique "profile" are what I was discussing. So far no digital circuitry can fully compensate for a relative who is dead set on dominating Thanksgiving dinner with their political views. Thus, I confined my discussion to the technical issues of the lens itself and nothing more.




"For example, that $50 mp3 player you mention...while digital audio is certainly something of an improvement over the days of vinyl and 8-tracks, there's a reason why brands like Bose and Nakamichi cost considerably more than your average I-Pod player ... "


I'm not at all certain how to respond to that comment. As I've mentioned before, my career has been in high end electronics and my perspective is that Bose and (the original) Nakamichi are at two very distant points in the audio universe. That both have traditionally been somewhat "pricey" does not equate to equal quality in both lines.



Yet, you are correct that not everyone "has a specific need to be a true audiophile". You are also correct when you imply there are numerous lower cost products which provide the less well heeled client a genuine taste of high end music reproduction.

Though, in that regard, the high end audio universe is sharply divided between the subjectivists and the objectivists. It would truly take this thread off into a tailspin should we begin discussing that issue. Just as it would if I were to say there is a strong contingent of "audiophiles" and music lovers who still feel vinyl is very much the media for music recording and reproduction and that a $50 MP3 player would only go a long way towards proving them correct.




My point, for those who may also have missed it, was simply the fact digital images must be processed in a way which can be seen as squeezing the middle ground of technical quality.

The op was asking specifically about lenses and I, therefore, did not concern myself with the camera other than as it necessarily relates to the use of the lens.

In the context of my post, IMO Photoshop is not the equivalent to the techniques of image manipulation used in a darkroom.

I never did the darkroom stuff when I shot analog. I never had the room for the chemicals and the set up.

Yet, I am unaware of any "corrections" which could so easily have been performed in a darkroom (to an analog film image) which would have corrected for chromatic aberrations from the lens. Lens distortions were equally simply "there". We accepted their absence as a sign of a higher quality camera and lens in those days.

Vignetting was a conscious decision of the photographer and not a consequence of their budget.

My point is, today the digital processor(s) any DLSR user will encounter may have camera AND lens profile corrections which can be achieved by simply mousing over a small box and clicking the appropriate adjustment function. That function doesn't even require the user understand what is being corrected let alone spot the imperfections and then make the numerous, discrete, individual and tedious adjustments which would have occurred in an analog situation to make such similar corrections.



The conclusion I have reached is, for good or bad, digital imaging software has lessened the final product differences between cameras and lenses in today's market.

Much of what a lower priced camera lacks when compared to a much more sophisticated piece of equipment can be digitally altered (in post production) to give a reasonable appearance of quality. It won't fool the dedicated pixel peeper but it will be more than good enough for the average consumer.



I have to add, the internet has had little to nothing to do with that function.

I hope that clarifies my previous post for you and others.