No, upsize the 20D shot to the same dimensions as the double size SD10 shot out of SPP,...13.7mp(?)
All 20D images are interpolated so comparing one with an interpolated SD10 shot should be a fairer test, yes?
It's great to see people understanding this issue. I suggest we use the terms "optical" and "interpolated" resolutions in the same way as the scanner industry, whose buyers all intuitively undersood this issue virtually instantly back in the 90s when this same issue came up.
Interpolating 20D to 13.5MP seems natural here. By the way I find interpolation useful on two counts: (1) some flaws cannot be visible at 100%, and interpolation blows them up, and (2) because usually print is the final destination for an image, it is useful to see images how the printer sees them: namely, the printer interpolates whatever comes its way to its native resolution [see discussions on interpolation and , especially, Qimage on Printer Forum].
Some printers do, some don't. Laser generated silver halide photographic emulsions won't care either way, and when/if those printers do interpolate to smooth extreme print sizes, it is on the order of 4000+ dpi. I'm not sure why we'd spend money and time worrying about image quality only to use a home printer.
Go to Printer Forum and you may be surprised; there many myths @ printers to be debumked (in particular, about 5600dpi resolution on inkjets), about relative quality of various printing processes. A $200 home printer, properly handled, can give you spectacular quality.
your star cirle is discernible on 20D shot [I had to resize it of course, this time with Lanczos]
You are on a good track, but forgot about colour separation. Printer driver first have to do a colour separation, e.g. CMYK, because printer can print only different intensity of colours from its cartidges. Stated resolution (e.g. 600 dpi) is describing the resolution of those primary colour dots, not fully coloured pixels. Therefore is dpi of Ink jets a bit missleading.
Not exactly if speaking of inkjet-printers.
It can give you spectacular quality compared to older home printers, but it's never going to expose then develop a true photograph for you.
Günter, you just repeated what I said, just in other words. Printers are not printing pixels we see on the monitor, but smaller particle of different size and colors that looks like it from the distance.
down sampling the native interpolated image from the sigma to the 20d native interpolated image should give the sigma an advantage, no? I compared the first two images (3504x2336) from the orginal post and after sharpening them both the same I see no sharpness advantage that some here claim the sigma has and the 20d image has more detail, not only in the backdrop, but also looking at the dogs nose, the sigma image had some jaggies on the watch clasp and the baileys label, the canon image was smooth. As far as this shot goes there should be little difference in sharpness at any print size.
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It does, of course, everything you said, but it does also something extra. By "native resolution" I mean the positioning accuracy of printhead. It is usually limited at 600-720dpi, even though you think you are printing 5600dpi. A good discussion of that is on Qimage website:
It does it for me every time!
--People here are going to see what they want to see no matter what,
but I figured I'd sharpen your jpgs and post it anyway.
Unfortunately I can't download the raw photos due to my slow dialup
so I had to go with your processing. I also don't do much raw
processing anyway.
http://www.pbase.com/paulyoly/image/40101464
I cropped the middle from each image and merged them, then
sharpened the combined image using a two layer process.
My conclusion is simple, the image quality is very similar, the
sigma shot shows much more sharpening halos, the 20d shot could
have taken even more sharpening. There are a few edges in the
sigma shot that are jagged that are not jagged in the 20d shot, i'm
sure some expert will explain this (sigmasd9?). The sigma seems to
have more contrast, i doubt this is the lens since sigmasd9 seems
to praise the canon so highly so it's either the sensor or raw
processing settings. Something I find strange is the difference in
the white sheet, the strands or texture looks larger in the sigma
shot, is this from upsampling?
Things you can't see in this test are the iso performance of the
canon, the great buffer and 5fps (which is just plain fun, but
unecessary for most shots.) I see no advantage for the sigma in
this test.
I'd like to see both shot with the sigma lens or canon, but of
course I don't expect you to go out and buy a lens. I appreciate
the comparison, it was interesting.
--
Narrow depth of field ahead
Use extreme caution
http://www.pbase.com/paulyoly/root
No it is from Aliasing. Lack of an AA filter. It is the same phenomena that produces 5 lines from 9 on the res chart in the review. As the details get smaller the actual ouput gets bigger. This gives the impression that it is show more detail when in fact it is obscuring the real detail and giving a bigger false pattern.
It is almost as much discernible on Sigma shot. I call it blurred dots anyway since the details are going to extinct and only my knowledge of real subject allows to "see" the stars.
Correct, but I wouldn't call it "lacking" for not having an AA filter. Bayer cameras don't have AA filters to blur out details, they have the AA filter for avoiding unsightly color aliasing. You will always get something wrong when taking pictures of details too small for the sensor. The "smudge it out" approach of an AA filter is no more "correct" than the aliasing we get without.
The false pattern is indeed false, but it does rarely obscure a real pattern you cannot capture anyway. The false blurring of an AA filter is often the bigger problem.
As for the resolution chart, the sigma is clearly not showing a "true" image when it merges nine lines into seven and then into five. But at least it shows a set of black and white lines, where AA-equipped cameras shows a single column of gray. The sigma photo carries more information - "there is lines" where the AA photo merely says "don't know - too high resolution for me". There was no gray in the original resolution chart, so the gray column is "wrong".
