Lens Performance with New Generation DSLR

[sanking]

One of the issues people will have with the new generation DSLR cameras that pack a lot of pixels on the sensor is lens quality. This will be true of both 15 mp APS sensor cameras like the Canon 50D as well as full frame sensor cameras like the Sony A 900.

In resolution testing the Canon 5D with several different lenses I found that the limiting quality for resolution was the sensor, not the lens. The theoretical maximum in terms of resolution of the Canon 5D is about 60 lines per mm, and what you get in practice is about 52-55 lines per mm.

In testing the Canon 50D, which puts 4752 linear pixels on a 22.3 mm sensor, the limit to resolution is definitely the lens, not the sensor. Using several different zoom lenses, including a couple of the expensive L lenses, I only got a maximum of about 80 lines per millimeter, whereas with a prime 50mm f/1.8 I was able to get 90 lines per millimeter.

Just food for thought for anyone planning to invest in a 22-24 mp full sensor camera. You are going to need some good optics to take advantage of the sensor.

Sandy King

[spotmeter]

One of the issues people will have with the new generation DSLR cameras that pack a lot of pixels on the sensor is lens quality. This will be true of both 15 mp APS sensor cameras like the Canon 50D as well as full frame sensor cameras like the Sony A 900.

In resolution testing the Canon 5D with several different lenses I found that the limiting quality for resolution was the sensor, not the lens. The theoretical maximum in terms of resolution of the Canon 5D is about 60 lines per mm, and what you get in practice is about 52-55 lines per mm.

In testing the Canon 50D, which puts 4752 linear pixels on a 22.3 mm sensor, the limit to resolution is definitely the lens, not the sensor. Using several different zoom lenses, including a couple of the expensive L lenses, I only got a maximum of about 80 lines per millimeter, whereas with a prime 50mm f/1.8 I was able to get 90 lines per millimeter.

Just food for thought for anyone planning to invest in a 22-24 mp full sensor camera. You are going to need some good optics to take advantage of the sensor.

Sandy King

This is great news, as I have a lot of Zeiss and Canon primes!

[pellicle]

Sandy

One of the issues people will have with the new generation DSLR cameras that pack a lot of pixels on the sensor is lens quality.
...
Just food for thought for anyone planning to invest in a 22-24 mp full sensor camera. You are going to need some good optics to take advantage of the sensor.

very good points but I would raise the following

• when using wide angle or photographing more distant subjects the subject level detail is going to be an issue. Testing is done (often enough) at a distance related to the focal length of the lens, when using wide angle (even 50mm) this can result in a need for much higher resolution than a telephoto (because feature detail will be smaller when photographing at normal distances). This is something which I cover in the latter part of this blog article. If chasing better wide angle performance I recommend photographers to begin looking at bigger formats (where you're using a longer lens too). I find that images take in with my 90mm on 4x5 hold more detail than images taken with my TS-E 24 on film (or even on a Digital). This point is not insignificant as the cost of better bodies (both outright and in requisite computing power to process images) is perhaps close to the costs of a reasonable 4x5 outfit.
• the bar is always being raised, but need it be so? If I like the results I get from a lens then with a higher density sensor (5D to 5D Mkii) then I'm comfortable that I'll be still as happy with the image as it will not be degraded. Perhaps I'll be able to print it more with out software interpolation, but it won't become suddenly bad. With colour photography (leave black and white aside for now) I feel I'll get better colour images from a 5D than from many scans of 35mm film. So if I have a lens which was giving me good results from scans of film, then I'msure it'll produce images of sufficient quality (I've had good prints made to 40cm wide from 35mm) on digital. I feel that this equates to 5D or better simply being better and unless you're using a chumpy zoom (like say a cheapie 35-80) that good images which you liked from your lenses will remain good images that you like on a better body (should you upgrade from 5D to 5D MkII).

Granted if you find that your DSLR is showing up your chintzy lens to be just that (Tamron 28-200 anyone?) and you hadn't noticed it on film before then upgrading your camera may come as a surpirise (if so its been a good learning exersize), but I don't really think that my 12 year old EF200 f2.8 will suddenly suck when I put a 5D II behind it rather than a 5D or 20D. I could see issues on my poor lenses back when I tried a Canon EOS 350D and didn't see much difference on my 20D.

Example:

I bought an EOS 630 some (like 17) years ago, it came with an EF35-70 lens which I thought to be "ok" for a walk about lens. My preferred lenses were my EF50 1.8 and an EF24 f2.8 ... years later when I got a 20D I found that the EF35-70 was rather soft and lacked contrast (which I suspected but rarely noticed on negs) when compared to the EF 50.

To some extent this can be 'compensated for' with use at smaller apertures and by a little 50 pixel radius ~ 20% sharpening in photoshop. I don't think it will look worse (than it already does) when used on a 5D MkII than it does on a 5D just you'll have higher magnification to deal with.

Magnification will always reveal more flaws, but as I mentioned above if the prints were satisfying they probably still will be.

IMHO the greatest change will be seen in going from APS sensor to Full frame as this will bring the edges into the picture (and there my old EF35-70 really falls down).

:-)

[sanking]

Hi Pellicle and Spotmeter,

Thanks for your comments.

Since I posted the original message on this subject I spent several week in Oaxaca, Mexico working with the Canon 50D. I had with me several zooms and a couple of primes.

My working procedures are probably different from those of most in that I try to always use the camera on a tripod, and use aperture priority with the lens set at an aperture that is not diffraction limited. For the Canon 50D that is just over f/8. Of course, the primes will give much better performance at wider apertures.

What I found in practice is that at f/8 all of the lenses, zooms and primes alike, gave about the same performance. So, if you are able to use your camera on a tripod and set the aperture at about f/8 or lower you should be able to get excellent results with the Canon 50D with both primes and zooms.

About noise. Since I use the camera on a tripod whenever necessary, with ASA set to 100, noise with the 50D has not been a problem, as some reviews suggested it might be. However, I generally run my digital capture shots through a noise reducing program as I like a smooth, creamy type look in my prints. Heritage of LF I guess.

Sandy King

[jd callow]

My experience with noise has been that it increases with length of exposure and at the ends of the scale. I also use tripods and aperture priority.

[pellicle]

Sandy

sounds (to me here in Finland) like an exotic location trip, hope you had a good time :-)

My working procedures are probably different from those of most in that I try to always use the camera on a tripod, and use aperture priority with the lens set at an aperture that is not diffraction limited.

sounds remarkably like mine ...

For the Canon 50D that is just over f/8. Of course, the primes will give much better performance at wider apertures.

ok .. interesting I have some general rule of thumb (though nothing clear) in my mind about this myself and thought it tended to get better by stopping down until you got to diffraction producing detraction of the image.

I think I'll do a few tests with my 50 f1.8 on my 10D (and publish it) to get a better 'feel for this' (thanks for the idea ;-)

What I found in practice is that at f/8 all of the lenses, zooms and primes alike, gave about the same performance. So, if you are able to use your camera on a tripod and set the aperture at about f/8 or lower you should be

ok ... again this matches my personal taste and operation with my camera, nice to see others find similar.

About noise. Since I use the camera on a tripod whenever necessary, with ASA set to 100, noise with the 50D has not been a problem, as some reviews suggested it might be. However, I generally run my digital capture shots through a noise reducing program as I like a smooth, creamy type look in my prints. Heritage of LF I guess.

interesting (the noise reduction bits), do you find that there is any significant loss of image quality? I was recently scanning some old film from my Japan years and found that it was interesting how once feature size shrank things turned from 'discernable detail' to fuzz. Specifically how broad leaf species and conifers differed.

anyway .. thanks for your test details

[pellicle]

JD

My experience with noise has been that it increases with length of exposure and at the ends of the scale.

I seem to observe that my images when its been minus 10 C or less seem less noisy than when its "room temperatures" ... its a pitty that my batteries don't like that sort of temperature (and give up the ghost)


:o)

[sanking]

Well, with the Canon 50D because of the small pitch of the sensor points diffraction limiting aperture is at just over f/8. F/11 is ok, but f/16 gives considerable loss of sharpness.

BTW, this would not be the same for the 40D as the sensor points are larger.

Sandy

ok .. interesting I have some general rule of thumb (though nothing clear) in my mind about this myself and thought it tended to get better by stopping down until you got to diffraction producing detraction of the image.

I

[sanking]

I think the noise reduction helps the image as it look a lot smoother if done right. A smooth image looks better to me than one with hard biting detail. Perhaps this is my large format background kicking in!

Sandy King

interesting (the noise reduction bits), do you find that there is any significant loss of image quality? I was recently scanning some old film from my Japan years and found that it was interesting how once feature size shrank things turned from 'discernable detail' to fuzz. Specifically how broad leaf species and conifers differed.

anyway .. thanks for your test details

[pellicle]

Hi

I think the noise reduction helps the image as it look a lot smoother if done right. A smooth image looks better to me than one with hard biting detail.

on a tangent here thinking about the advantages of sensor density to record more of what the lens can produce has me thinking of the Panasonic G1. I suspected that it would do well, and looking between images on DPReview it indeed seems that the 100iso image clarity of that will go close to the 5D.

Some years of using tiny compact cameras for snapshots (and metering for my 4x5) has spoiled me into wanting a compact which is better than 35mm can be and not much bigger to carry than my Pentax digital spotmeter (which now gets left at home most of the time)

I think I'm going to be switching from my Canon outfit soon