1.6 cropping and lens quality

[kram]

I have read enough lens discussions and a common downside of many lenses is that the edges are bad.

With the 1.6 cropping, will those edges not get cut out? That would suggest that even a lower quality lens (from the edges perspective) be a better performer on the Drebel series and the 20D?

[tim]

With EF lenses the edges aren't used, with EF-S lenses they are. You're right, this means you're using the "sweet spot" of the lens for most of your frame.

[chris clements]

But, aren't EF-S lenses computed so the light hits the chip closer to 90 degrees across the whole frame, which wasn't a significant image quality factor for film, but is for digital?

So, what you gain at the corners with EF lenses, maybe you lose across the whole picture?

[CyberDyneSystems]

Chris.. mostly the quality issue that "croppped up" ( ;) sorry) with Film lenses on Digital bodies regarding the angle the light hits the sensor was on Full Frame Sensors.. the center of which.. the sweet spot.. is getting more direct angle of light than the outer edges.. causing often enough a very visible "vignette" on cameras like the 1Ds

When the same lens is used on a 1.6x crop camera.. that light fall off on the outer edges is not present (or at least not as present) and is rarely perceptible at all. By using the "sweet spot" the angle of light is allready "optimized for digital" without further lens engineering.

You are however correct.. that with the EF-S and other manufacturers "DI, DG, DX, D-whatever" lenses the claim is that they are "digitally engineered" or "Optimized for Digital" to work better with CMOS/CCD sensors than the traditional 35mm film SLR lens was, just as you describe.

If not.. then the EF-S lens would exhibit on the 1.6 cameras the same sort of darkened outer edges that is possible with film lenses on the 1Ds and other full frame DSLRs

[montreal]

Very informative thread. Thank you Cyber.

[DavidEB]

On the other hand, if you magnify your photo more (by the 1.6 factor) to get the print, the APS size sensor is more demanding of lens performance in the center of the frame.

I'm just guessing with this next one, but since the APS sensor reduces the largest angle that light hits the sensor (eg, the 1Ds at the edges sees light hitting at a flatter incident angle) then perhaps these cameras are less susceptible to flare as well. But as I said, that's just a guess.

[chris clements]

On the other hand, if you magnify your photo more (by the 1.6 factor) to get the print, the APS size sensor is more demanding of lens performance in the center of the frame.

You've lost me- why are you magnifying the image from the smaller sensor to get the print?
To get the same 'coverage' (trying not to open another fov/dof/perspective debate) at the same focal length on both cameras, it would be the full-frame photo you'd be magnifying (cropping).
That would make the APS DSLR less demanding, not more.

What am I missing?

[kram]

Sorry, but going back to my original question - if the lens is not a EF-S lens or 'optimized for digital', the quality of the lens should be better on a Drebel than on a 1D. Right?

Are there such lenses - not liked by 1D owners but found acceptable by 20D owners? I dont see any such posts....

[DavidEB]

Chris --

let's say you want to make a 4x6 print. From your 35mm full frame camera, you enlarge the image by about a factor of 4 (long edge goes from 35mm on the sensor to about 150mm on the print). From your APS sensor camera, you enlarge the image by a factor of about 7 (from 22mm up to 150mm). In technical terms, the circle of confusion is smaller on the 1.6 crop camera.

kind regards,

David

[CyberDyneSystems]

Sorry, but going back to my original question - if the lens is not a EF-S lens or 'optimized for digital', the quality of the lens should be better on a Drebel than on a 1D. Right?

Are there such lenses - not liked by 1D owners but found acceptable by 20D owners? I dont see any such posts....

Yes.. absolutely.
1Ds owners need the absolute best optics to feed there cameras.
Lenses that would show vignette on the full frame sensor can be excellent on the 20D.

Most of the favorite Sigmas we all love are not as good on full frame cameras.. the 70-200mm and 50-500mm are good examples.. especially the 50-500mm which can show very dark outer edges. 1Ds owners sometimes say the 70-200mm EX gets soft at the edges.. Many 10D owners were baffled by people saying this (including myself) .. as those soft edges were "not it the picture" on the 1.6X

Even the 100-400mm L shows darker edges on the Full frame.. in fact it shows it on the 1D 1.3X sensor as well. (but not as bad obviously)

Of the hoards of 28-135mm IS lovers, probably 95% use 1.6X cameras... you'll find posts from 1Ds and even 1D owners who say the lens is not good.... etc etc etc

[felix21685]

good information...thanks guys...awesome :) tells me i need to stick with a 1.6 crop camera..so there is a limit of how much i could spend aha :)

[RDKirk]

Adding to some of the other information:

One of the most significant features of "designed for digital" lenses I've discovered is the rear element multicoating. Digital sensors are as reflective as mirrors. Unlike film, they reflect a great deal of image light back into the mirror box, where it can reflect back from the rear element (and back and forth millions of times) during the exposure--causing flare. Film lenses did not have multicoated rear elements--multicoating allows the light that bounces back to the lens to exit straight through the front of the lens, rather than reflect back into toward the sensor.

This can make a BIG difference. I've found my Tamron DG zooms clearly beating my Canon non-L (not rear-element-multicoated) prime lenses at resisting flare on my 10D and 20D.

Lenses are capable of much more resolution than even the 1Ds sensor can provide. The system resolution is always less than the lesser of the lens and the medium. The lens by itself, if you were to use it as the optic of a scope and peered through it (the "aerial resolution" )is capable of several hundred line pairs per millimeter. If the medium is only capable of 100 lppm, the total system resolution would be less than that--perhaps 70 lppm. If you got an even better lens, you could pull that up a bit, but it's often more efficient to get a higher-resolving medium.

High-resolving APS-C sensors--like the Nikon D2x--do demand more resolution from the lens, but the average SLR lens has the resolution to spare, which is why the 12mp Nikon resolves nearly as much as the Canon 1Ds 16mp (granted, resolution alone isn't everything, but I'm talking only about resolution at the moment).

The major problem with current lenses on the 1Ds isn't resolution, it's other problems as have been discussed. Canon lenses are capable of more resolution than can be seen on the 1Ds, as a film user can discover if he makes a test with the super-resolving Kodak Technical Pan film. Resolution-wise, it pulls significantly more out of the lens than does the 1Ds.