Digital cameras and the lens dilemma

[Petes]

A common theme in the last couple of years has been a lot of disappointment in image quality especially for those of us shooting with so-called "full frame" slr's. I personally use Kodak's slr/n and have just never been totally satisfied with the results I've been getting. I also have Nikon's D100. When I put the DX 18-70 on the D100 I was amazed at the resolution that combo produced; even better than what I could get with the 50mm 1.8 and the 60mm macro.

My theory is this, those of you who remember back in the days of Kodak's Tech Pan film ran into similar issues with resolution. Even Leica's offerings weren't totally up to what that film could reproduce. I think what's happening right now is that the lenses made for film that we are trying to use on digital cameras just cannot get it done especially on the larger sensors. Michael Reichman ran into this when he first started testing the original Canon 1DS. His statement at the time was that nothing other than top quality lenses were going to do justice to the full frame sensor.

So it looks like a whole new generation of lenses will need to be created that will give us what we are looking for. Nikon, Canon, Sigma, and others are all producing "digital only" lenses but they still have a ways to go. I'm not at all surprised that Nikon is sticking with the APS sized sensor for now because they probably realize that nothing they manufacturer is going to provide the coverage and resolution required by the 24x36 sensor.

Comments? Rebuttals?

[badpickev]

to clarify a point. Sigma is also upgrading their complete lens line up so the work better with digital. Sigmas DG designation is a film lens that is optimized for digital. That implies that they added a coating to reduce abberation on a digital camera. Some people are starting to comments that the Dg lenses seem a slight better than the non DG ones. Their DC lens line is made exclusively for APS-C sized sensors. You can use on film or FF but you will get vignetting

[Narsuitus]

If someone produced a digital SLR that was as sturdy and reliable as a Nikon F, F2, F3, F4, or F5 (I omit the F6 because it is too new to evaluate), was full-framed like the discontinued Kodak digital SLR/n, produced images equal in quality to those produced by the Fuji S2 or S3 digital, was priced like the Canon Digital Rebel, and handled old and new Nikon lenses like the Nikon F4, I would have the digital SLR that would meet my needs.

[scoundrel1728]

Originally Posted by Narsuitus

If someone produced a digital SLR that was as sturdy and reliable as a Nikon F, F2, F3, F4, or F5 (I omit the F6 because it is too new to evaluate), was full-framed like the discontinued Kodak digital SLR/n, produced images equal in quality to those produced by the Fuji S2 or S3 digital, was priced like the Canon Digital Rebel, and handled old and new Nikon lenses like the Nikon F4, I would have the digital SLR that would meet my needs.

If a camera manufacturer could make a camera with all those attributes in quantity and still make a profit, it would be months before supply could catch up with demand. What are you going to shoot with while waiting for one?

Sounds like Petes is saying that the resolution capability of the imagers on full-sized models has surpassed the resolution capability of today's 35 mm lenses. Not sure I agree with that; it could also be possible that the anti-alias filter is also mucking up the ability of some of these cameras to resolve fine detail. Of course, moiré becomes a problem if the AA filter were removed. It's a tradeoff.

[Wilt]

>>Sounds like Petes is saying that the resolution capability of the imagers on full-sized models has surpassed the resolution capability of today's 35 mm lenses. Not sure I agree with that; it could also be possible that the anti-alias filter is also mucking up the ability of some of these cameras to resolve fine detail.<<

I read a claim along the lines of sensor resolution > lens resolution, so I ran the numbers myself to validate or disprove. If you look at the pixel pitch of the 12MP Canon 5D and look at how much resolution is provided on per-mm basis, and if you assume a 'good' (not 'spectacular') lens can resolve 64 line-pairs/mm, it computes out that the 5D is right at the threshold of outperfoming many (most?) lenses. One of the highest resolving 35mm format lenses made topped out at 128 lp/mm and that is 'spectacular', and most 'excellent' lenses might be able to get up to 80 lp/mm at a few apertures.

[badpickev]

Peter, maybe you are looking at this from the wrong perspective. you are describing the down fall of digital camera in general. With film we got a new camera when the limitation of the old camera could no longer be tolerated. It seems we upgraded bodies once every 5 years or so. If we wanted a different look we changed our film (sensor). The major tech advancement was going to AF. This forced everyone to upgrade to newer bodies. Somepeople actually started upgrading bodies every 3-4 years. Now in the digital world the sensors are constantly being refined. The sad part is once a camera sensor gets outdated, there is no replacement. The bodies really are not advancing that much. Why cant the manufactures allow us to put upgraded sensors in our existing bodies?

[hartcons]

But isn't it true that if you use a film lens on a digital body with a lens factor (my d70 is 1.5x) that you are only using the center portion of the film lens and thus you are more in the sweet spot of that lens with digital? But I was also told by an Olympus rep (they went digital only for their e-system although you can get an adapter for their old film lenses) that film lenses don't have enough resolution for digital cameras.

I do think I notice a certain difference in clarity between shots with my e-300 and olympus digital lenses vs. my d70 and nikon film lenses. But then again is it always desirable to have your pictures look like they were taken with an electronic microscope? In the 3D animation world one of the first things you're taught is to "dirty up" your pristine computer images to avoid that "computer" look. So maybe a slightly grungy film lens would in some ways lead to more interesting pics. Maybe something like the debate about cds vs. records (I've been playing records again recently and really enjoying the sound, not to mention the price).

Also, as I understand it our digital cameras start out analog and then there's an A/D conversion in there somewhere. So maybe part of it is the quality of the A/D conversion.

I like the idea about being able to pop in a replacement CCD! Kind of like a reallyfirmware upgrade

[Narsuitus]

Originally Posted by scoundrel1728

What are you going to shoot with while waiting for one?

While I patiently wait for the digital SLR that I need, I will continue to shoot with my film-based systems and my fixed-lens digital. I will also continue to use my film scanner to convert film images to digital images when I need to.

[Petes]

Badpickev,
>>Peter, maybe you are looking at this from the wrong perspective. you are describing the down fall of digital camera in general. The sad part is once a camera sensor gets outdated, there is no replacement. The bodies really are not advancing that much. <<

I'm not predicting the downfall of digital, I'm just saying they will have to crank up the quality of their lenses to match what digital sensors can produce. There are some exceptions, some of the Canon L's are reputed to be good, the Nikkor 28-70 and the 70-200...; well, that was a short list! As I mentioned previously, the Nikkor DX 18-70 does a fine job on the D100. Hopefully this is a trend, we'll see with the just announced Nikkor 18-200 VR. The price is certainly up there.

Does anybody know how the Leica lenses are fairing on the DMR? That would be interesting.

>> Why cant the manufactures allow us to put upgraded sensors in our existing bodies?<<
Why indeed! At a local digital show a couple of years ago I asked the Canon guy that very question, he just shook his head and said "no, they will never do that". There have been 3rd party lens makers for years. Maybe some enterprising young upstart will start making upgraded sensors for existing digitals. Anybody up for Foveon sensor in their favorite Nikon or Canon?

[Petes]

Hartcons,
>>But isn't it true that if you use a film lens on a digital body with a lens factor (my d70 is 1.5x) that you are only using the center portion of the film lens and thus you are more in the sweet spot of that lens with digital?<<

That's the theory but I think something else is going on with the film lenses as your Olympus guy stated. I've used four different film lenses on my D100 and slr/n and, (OK, I'm being picky but for the money invested I have a right to be!) the results are good but not great and that's with using a tripod, mirror lockup, etc...; maybe I'm too fussy!

[hartcons]

I have a nikkor 28-200 film lens and was never that thrilled with the resulting images on my nikon d70. But I just picked up a Nikon N75 film body (I know, I'm going backwards!) and suddenly I'm getting nice sharp pictures and liking my 28-200 lens a whole lot more (although it still autofocuses like it has had way too much to drink). So maybe all-digital is the way to go but if you get lenses for the smaller sensors and then suddenly get a full-frame digital I don't even know if they'll work (then again you can pick up an n75 for under $200 and have a full-frame analog that works with your film lenses).

[scoundrel1728]

Originally Posted by hartcons

But then again is it always desirable to have your pictures look like they were taken with an electronic microscope? In the 3D animation world one of the first things you're taught is to "dirty up" your pristine computer images to avoid that "computer" look. So maybe a slightly grungy film lens would in some ways lead to more interesting pics.

False analogy. In 3D animation, you are starting with an ideal object and "dirtying it up" to give it the imperfections of real objects. In photography, you are starting with real objects, not ideal ones, that are already "dirtied up" and making visual reproductions of them. Doesn't have anything to do with the rest of my post, but I thought this argument interesting even if I didn't agree with its line of reasoning.

Originally Posted by hartcons

Also, as I understand it our digital cameras start out analog and then there's an A/D conversion in there somewhere. So maybe part of it is the quality of the A/D conversion.

Yes indeed! Careless design can greatly degrade the analog data through noise and interference, but it becomes more or less "bullet-proof" once it is digitized.

Originally Posted by hartcons

I like the idea about being able to pop in a replacement CCD! Kind of like a reallyfirmware upgrade

The idea sounds appealing, but the devil is in the details. It isn't simply a matter of dropping in a new imager. The new imager has to be aligned with tight tolerances to ensure that it is truly at the image plane of the lens and is truly flat and perpendicular to the optical axis so that the lens will focus properly on it as expected.

Furthermore, if the new imager design is a substantial upgrade and not just a replacement, this will almost certainly require other hardware changes, perhaps more A/D converters or a faster clock rate, and a firmware change as well to handle the different number and configuration of the pixels. Even for a drop-in replacement, the new imager must be color calibrated and the hot pixels mapped out.

Result: upgrading the imager would probably cost more in parts and rework than the added market value of the upgrade.

[blumesan]

Originally Posted by hartcons

But isn't it true that if you use a film lens on a digital body with a lens factor (my d70 is 1.5x) that you are only using the center portion of the film lens and thus you are more in the sweet spot of that lens with digital?

I don't believe that's true.* Based on my (rudimentary) understanding of optics you are using the full lens regardless of how the image may be cropped.* "Full" meaning, of course, to the extent that the aperture is open.* Pleased to hear any comment, pro or con, from those more expert.

Cheers,
Mike

[hartcons]

I thought the idea was that the films lens would throw a full circle but the digital sensor (at least one with a lens factor) is small so it sits well inside that circle (so you are basically throwing away light that otherwise could be used but this might be good in some ways because problems often happen out at the edges). I could be completely wrong but I thought this was how it worked.

[blumesan]

Originally Posted by hartcons

I thought the idea was that the films lens would throw a full circle but the digital sensor (at least one with a lens factor) is small so it sits well inside that circle (so you are basically throwing away light that otherwise could be used but this might be good in some ways because problems often happen out at the edges). I could be completely wrong but I thought this was how it worked.

Well you are right, that the lens projects a full circle of light that is, in the case of a digital sensor, much larger than the size of the sensor.* So what happens is that part of the image outside the sensor is thrown away.* Nevertheless the entire lens contributes to that part of the image which does fall within the bounds of the sensor.* Do the following thought experiment.* Stop down the aperture.* This does cut down the portion of the lens which gathers light and contributes to the image.* But the entire image is affected, including the central portion where the digital sensor is located.

There is one instance where you are correct in practice, but not in theory.* With lenses which have significant light fall-off or diminished MTF at the periphery of the image are in fact being used closer to their "sweet spot" with a smaller (digital) sensor.