my 17-55mm IS vs 50mm 1.4, results and Question, is my 17-55 soft???

I think that looks better.

I second not shooting in low light. The prime is wider aperture so will focus more accurately in low light. I know my nifty is terrible in low light for example, yet focusses accurately and produces a sharp image where there's plenty of light.

To me the 17-55 shots look OOF more than anything. When I owned the17-55, the 50 would beat it by a hair at f/2.8 and they were about the same at f/4. My 17-55 was a lot sharper than the posted crops....to the point where I wonder if the posted crops are just showing a low light focus issue.

get the time to retest the 17-55:
f/2.8(above) vs f/4.0(bottom)
now with good light from the window:

From those pics I don't think there's anything wrong with your lens. Primes are almost always sharper than zoom lenses (if you're pixel peeping at 100%). Try doing the experiment with your 10-22 and see if that's as sharp as the prime - I suspect it's no better than the 17-55. The 17-55 does seem to respond well to some sharpening at 100% but there's really not much point unless you're cropped the image down and want to use the remaining in a large print.

However you're forgetting the advantages of the 17-55 - first of all you have a lens capable of giving good results from 17mm to 55mm. When you're out and about in real-world scenarios then the zoom will give you images you simply couldn't get with a prime, plus you have the option of going wide angle or a slight telephoto giving you infinitely more choice.

Quality-wise, instead of pixel peeping, print the pics out and see if anyone can tell the difference between the prime and the zoom - in most cases I'd wager they can't (unless you're using a really wide aperture on the prime to give the images more bokeh).

The second advantage of the zoom is the image stabilisation. Try taking some pics handheld in low light and see which gives you best results - I suspect it will be a close race. On the one hand the prime will give you a faster shutter speed, on the other the IS unit will be keeping the image stable at lower shutter speeds on the zoom. For moving targets the prime will be better but on a test like this I think you'll find it's a close race - unless you have exceptionally steady hands then the zoom might give you a clearer image purely because it can correct for shaky hands.

By the way, the only zoom lens I know of capable of equally prime lenses is the 70-200 which is sharp even wide open. The colours also seem to be richer, I guess it's down to the special coatings they put on L lenses.

JoYork wrote in post #4955192
From those pics I don't think there's anything wrong with your lens. Primes are almost always sharper than zoom lenses (if you're pixel peeping at 100%). Try doing the experiment with your 10-22 and see if that's as sharp as the prime - I suspect it's no better than the 17-55. The 17-55 does seem to respond well to some sharpening at 100% but there's really not much point unless you're cropped the image down and want to use the remaining in a large print.

However you're forgetting the advantages of the 17-55 - first of all you have a lens capable of giving good results from 17mm to 55mm. When you're out and about in real-world scenarios then the zoom will give you images you simply couldn't get with a prime, plus you have the option of going wide angle or a slight telephoto giving you infinitely more choice.

Quality-wise, instead of pixel peeping, print the pics out and see if anyone can tell the difference between the prime and the zoom - in most cases I'd wager they can't (unless you're using a really wide aperture on the prime to give the images more bokeh).

The second advantage of the zoom is the image stabilisation. Try taking some pics handheld in low light and see which gives you best results - I suspect it will be a close race. On the one hand the prime will give you a faster shutter speed, on the other the IS unit will be keeping the image stable at lower shutter speeds on the zoom. For moving targets the prime will be better but on a test like this I think you'll find it's a close race - unless you have exceptionally steady hands then the zoom might give you a clearer image purely because it can correct for shaky hands.

By the way, the only zoom lens I know of capable of equally prime lenses is the 70-200 which is sharp even wide open. The colours also seem to be richer, I guess it's down to the special coatings they put on L lenses.

yeah the 70-200 is no doubt the best zoom lens out there, even i don't have it, the reviews and pictures i see on pixel peeping, all week i have satisfied
but at f/4.0 still too slow jo , but i assume that you already had the 85 1.8 for that situation,.. right,. good combo,..

well back at 17-55.,. ok, all fix on softness,..
Any dust issues jo? i have it , well it's not affecting my IQ, but when i test it on a white BG at f/8.0 above i can see a soft black spot where the dust is present,.. (i'll post it later), i feel that if i had those dust, i may affecting the cost of this lens, can i still clean/calibrate the dust on the lens even the warranty is over? i'm worried coz of this,.. or maybe clean it by myself, using the trick that Roger Cicala does:https://photography-on-the.net/forum/showthre​ad.php?t=348343
, never try it thought i feel scared that my warranty is over by doing that. still 9 month warranty btw,..

I've owned both, In light the 17-55 will beat or par with the 50mm in all apertures, but in low light the 50mm will win hands down thus making the 17-55mm a good walk around.

Are you sure it's dust on the lens or dust on your sensor? As far as I know, dust on the lens isn't an issue as it's too close to the lens to be in focus but dust on the sensor can be a problem. Have you tried using the sensor cleaning option on your 400d?

I worried at first that f/4 would be too slow (partly why I went for the IS option) but I find it's not too slow at all. I don't use it indoors (my house isn't THAT big that I need 200mm lol) and in the day it's fine. This pic for example was 1/640 at iso 100 at f/4.5 - if I need a faster shutter speed for action I'll just increase the ISO. For static scenes I can handhold as low as 1/30th at 200mm which is fine for me.

I do love primes though - it's just knowing when to use zoom and when to use prime. Right tool for the job and all that!

its obvious that a prime lens will beat a zoom hands down. the second test looks decent. i would be happy with that performance from a zoom.

Second test looks fine, I think the first test was OOF.

paten wrote in post #4955311
Any dust issues jo? i have it , well it's not affecting my IQ, but when i test it on a white BG at f/8.0 above i can see a soft black spot where the dust is present,.. (i'll post it later), i feel that if i had those dust, i may affecting the cost of this lens, can i still clean/calibrate the dust on the lens even the warranty is over?

What you're seeing is dust on the sensor of the camera, not dust in the lens. If you get a lot of dust in the lens it may show up in images in the form of flare or reduced contrast, but it won't show up as spots in the image.

The 50 1.4 stopped down to f2.8 should be sharper than the 17-55 wide open, sure. That said, the 17-55 is one of the sharper lenses out there so I wouldn't worry too much.

In situations like this, where the subject isn't moving, the 17-55 would be just as effective as the 50 1.4. It's when you need the extra stop for shutter speeds that the fast primes really shine.

paten wrote in post #4954752
sharper than the previous, but...
it can explain that the prime is much much better used at low light condition, right???

you're right!! my camera "is" the problem, when i use the 10-22 or the 50mm, the spot is stil there,..
if i have the time i'll go clean the CMOS sensor at Canon, hopefully it'll disappear,..

jo, i saw you're gallery at flickr, and most of the shot is in daylight, well, different from you, my shot is often used at night, that's why you love you're 70-200 f/4 so much,..

if you use it on night/poor light condition, the 50mm 1.8/85mm 1.8 will be the substitute i presume,..
again, thx 4 all the reply all

I can only handhold my 50 1.8 at about 1/50th of a second or it produces a blurry image due to handshake.

Both my 17-55 and 70-200 can be handheld at much slower shutter speeds thanks to their IS systems.

For night photography I prefer a tripod anyway...