50D shows lens flaws or poor technique?

[racingmoose]

First, I want to thank everyone (especially Bob) who posts such useful and informative information here.  I've read many forum posts and reviews on the 50D and there is one area I'm still a little confused about.

There seems to be strong opinion that the 50D is less forgiving and will show a slight missed focus or exposure more than the 40D will for example.  Also, that minor lens flaws will be more evident.  Is this the case?  And I'm not so much concerned about the pixel "peeping" level.  I'm more concerned with what I consider real world uses such as prints ranging to 16x20 in my case.

Thanks!

[Bob Atkins]

I don't believe the 50D will show these effects any more than the 40D does, i.e. I don't think a higher resolution sensor can give rise to a lower quality image due to the higher resolution of the sensor.

You may certainly lose the advantages of the higher resolution sensor if the lens has lots of aberrations or if you miss focus, but in the worst case you'll get the same image quality as you would with an equal amount of defocus or aberration on a 40D.

There are ways in which a higher resolution sensor image may be "worse". For example if the noise level is higher due to the pixels being smaller. It's possible you might get different moire fringing if the low pass filter used is less effective than that on a lower resolution sensor. However these are effects that are only incidentally related to resolution. You could get the same effects in a low resolution sensor of a different design.

If you find a site giving examples of how the higher resolution of the 50D actually makes images worse, I'd be happy to review their methodology and see if I agree with their conclusions. So far I have not seen any such pages, just anecdotal reports with little or no evidence to back up the claims. There are lots of things you can do wrong to make the image worse!

One common error is to compare 100% crops from a high and low resolution sensor. In that case people often fail to realize that the crop from the higher resolution sensor represents a crop from a physically larger image than the equivalent crop from the low resolution sensor. This means that the crop from the high resolution sensor may look less sharp, even though if both images were used to make the same sized print, the one from the high resolution sensor would look sharper!

[racingmoose]

Thanks for the quick reply!

I haven't seen any image samples showing or proving the 50D will magnify a slightly missed focus/exposure or a lens flaw more than the 40D.  However, some people are mentioning it as though it's fact in forums and I read a review that also mentioned it (I'm trying to find which review it was). 

Thanks for your explanation.  I think that will help others like myself who have read the many reviews and forum posts about the camera.  The review you posted was a big help also.  Many of the reviews and comments about the camera revolve around the pixel level rather than what the image will look like in print or at normal viewing size.  I think that has lead to a lot of confusion.  Other comments, such as the one I asked about where some say the extra resolution requires perfect everything or the mistake will be magnified have also created a lot of concerns and confusion.  It gets difficult wading through some of this stuff.

Thanks again for your explanations.

[Bob Atkins]

If you haven't read it, you might also find this article interesting:

http://www.bobatkins.com/photography/digital/canon_eos_50D_resolution_confusion.html

It's a comment on some other "myths" on the 50D which seem to propagate on the web.

[racingmoose]

That's a great article and helps clear up some of what's being put out there about the camera. 

If you're interested, here's some info on luminous landscape that mentions the need for better lenses, focusing technique, etc.
http://www.luminous-landscape.com/reviews/cameras/50d.shtml

"The move from 10 megapixels to 15 megapixels really does make those nasty lens aberrations significantly more difficult to deal with. From now on, photographers working with cameras having the resolving potential of the 50D (or better) will need to choose lenses very carefully. And they will have to learn to focus carefully as well."

"My contention is that the Canon 50D ushers in a new era where we will need distinctly better lenses and finer focusing skills than we have needed thus far with digital SLR cameras."

"It tends to make lens aberrations and errors of judgment (such as using too small an aperture) more obvious "

[jodaco]

you left off the critical part of your final quote:

"...when viewing on screen at 100%, even if the final print is not much different."

Ironically this is the same site that demonstrates that the G10 can produce results as good as Hasselblad H2 and P45+ at the same print size!

http://www.luminous-landscape.com/reviews/kidding.shtml

[Bob Atkins]

It's quite true that more modest cameras (such as the G10) can indeed compete with even medium format digital cameras - as long as you're shooting at minimum ISO settings (Say ISO 50 for the G10) and as long as you don't try to make huge prints.

However if you boost the ISO, make larger prints or crop the image significantly, then the superiority of the larger format shows itself.

On my 17" diagonal monitor (1280 x1024 display), which shows an image 12" wide, a 100% display of an EOS 50D file corresponds to looking at aection of a print which is approximately 30" x 45". It's not surprising at looking at 100% crops revels some image defects! With an EOS 5D MkII, the corresponding 100% display equivalent print size is 35" x 52.5"

100% viewing is a very severe test of image quality. Much more severe than viewing a 14x20 print.