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28mm f/1.8 softness + unpredictable?

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zimpff

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hello --

so i am using 20D with 28mm f/1.8 and i am getting quite unpredictable results. it's very strange but sometimes the images are super sharp and very nice and sometimes they are are just totally off. naturally at 1.8 low light focusing is not ideal and unlikely to get good results, but even outdoors at 2.8+ i get softness.

do others have similar experiences? in what range do you use your 28mm? there is something i really like about this lens: built, size, feel, and really want to keep it, but may be i just haven't mastered it yet.

thanks!
 
Hard to say...

Does the 20d have the cross type higher precision focusing spot in the center? Use that in lower light levels especially.

Some of this, depends on how you're using the camera, how close you are to your subject, and it could also be camera shake.

Interesting note - a friend of mine, at my suggestion, got himself a 50/1.8 on his 400d. Thought he could conquer the available darkness world. Was bitterly disappointed. Why? The 50, at 1.8 had zilch depth of field and he thought a fast lens alone would make low light photography a breeze. He had camera shake too.

I can tell you that my 28/1.8 is a quite good performer, low flare, nice colors and contrast, very little vignetting (regardless of the "reviews" out there, this lens does not vignette badly). Its my standard lens, and I like a bit wider seeing lens as a standard (ie, 35mm on a 24x36 format).

How about posting some images, so more help can be given?
Livin' the blues, one note at a time
 
I really enjoy using the 28/1.8 USM on my 20D as well. Eventhough I have the 17-55/2.8, for street photography I almost always use the 28/1.8.

However, corner softness is the major drawback of this lens.

The center of the image can be razor sharp. I've done tests with it and found that it is at its sharpest at f5.6.

But on every f-value the corners stay soft, much more than you would expect on a lens in this price range.
 
Using the 28/1.8 on a 30D (basically the same as a 20D), I found that the central 70-80% of my photos were extremely sharp at f2.8. This was consistent. I also found the 28/1.8 to be a stellar focuser in low light - one of the very best. Sounds like your experience has been very different than mine. I used center point focusing only. If you're using all the focus points, you might want to try sticking with the center.

--
Amin
 
zimpff said:
hello --

so i am using 20D with 28mm f/1.8 and i am getting quite
unpredictable results. it's very strange but sometimes the images
are super sharp and very nice and sometimes they are are just
totally off. naturally at 1.8 low light focusing is not ideal and
unlikely to get good results, but even outdoors at 2.8+ i get
softness.

do others have similar experiences? in what range do you use your
28mm?
Click to expand...
I used to own this lens until about a week ago; sounds like you may be have focussing difficulties because the central 70-80% of the frame should always be very sharp from f/2.2 and stopped down and should be very nice at f/2.0. Poor light did challenge my 28 1.8 when near wide open but usually was OK outside. I did find though that I had better shaprness at objects at

I would suggest doing some focus tests to check consistentcy of focus. A trip to Canon with your camera (if under warranty) might help if focussing is the problem. Sigma have sorted out my 150 2.8 macro and replaced my 30 1.4 with a much better (nearly perfect) copy.
 
BanderSnatchReverb said:
I've not noticed much softening on the edges... makes me wonder if
I should check it out more closely.
Click to expand...
Usually soft edges are not a problem at wide apertures as they will not be in the range of the Depth of field.

The 28 1.8 should be sharp across the frame at f/5.6 on a 1.6 crop camera (perhaps f/8-f/11 needed for pixel peeping with a 1DS?).
 
the differences MUST be with the camera settings, because the lens elements do not change. the glass is the same,a nd it's a prime lens. the only thing that's changing is the focusing elements. try focusing on something near and something far, and somethin gin the middle. compare those results. maybe you are getting soft images when focusing near infinity? or near macro?
 
There are a number of reasons I prefer a prime when doing street photography. It does not necessarily have to be the 28mm on my 20D (witch makes it into a 45mm lens).

The most important reason is that I know beforehand what I'll see though the camera when I take the picture. This allows me (I feel) to work faster.

Another reason is that it's less bulky than my 17-55. This means it's lighter and easier to handle and it also attracts less attention. This might only play in my head, but somehow I feel more comfortable getting close to people with a simple looking lens than with a zoom-lens. I feel that a zoom lens comes across as more intrusive. Especially if you need time to zoom in or out and considering the length of the lens at 28mm to 55mm.

So working with a prime allows me to work very fast. In the way I take the pictures, but also in handling of the camera.
 
folk3 said:
....... also attracts less
attention. This might only play in my head, but somehow I feel more
comfortable getting close to people with a simple looking lens.
Click to expand...
Which is precisely why I keep three Leica M's here. Yes, the small Canon 400d is not too much larger than a Leica M (body) but the lenses... even teh 28/1.8 is huge compared to the 35/2.0 or 50/2.0 Leica lenses, or event the 28/2.0 Leica lens for that matter.

--
Livin' the blues, one note at a time
 
so i went on a road trip the last 3 days and had my 28mm and a 70-300mm with me. and i am shocked how poor the sharpness of the 28mm is as compared to the 7-300mm. i took some nice landscape shots and as they came out of the camera they are very very soft. i am really bummed out about it. i am posting a few examples. that's without any processing. is this the result one would/should expect? or may be i am just doing something wrong. i agree that sharpness seems really bad at infinity but even close it isn't that good. when you say a trip to canon, what do you mean? sending it in? it is still under warranty.

thanks for all your help!








KRobA said:
I used to own this lens until about a week ago; sounds like you may
be have focussing difficulties because the central 70-80% of the
frame should always be very sharp from f/2.2 and stopped down and
should be very nice at f/2.0. Poor light did challenge my 28 1.8
when near wide open but usually was OK outside. I did find though
that I had better shaprness at objects at
although that was pixel peeping.

I would suggest doing some focus tests to check consistentcy of
focus. A trip to Canon with your camera (if under warranty) might
help if focussing is the problem. Sigma have sorted out my 150 2.8
macro and replaced my 30 1.4 with a much better (nearly perfect)
copy.
Click to expand...
 
could be you or the lens but mine was very sharp @ f2.8 on my 20d and focussing was very fast and accurate.

ed rader

--



'One often has mixed feelings about relatives, but few people could identify serious problems in their relationships with dogs.'

-- Anonymous
 
it is hard to tell what exactly might be causing the softness, but it is easy to tell that it is there and it shouldn't be. you might want to run some more controlled tests (with a tripod and mirror lockup and good light, and not too close to the camera) to eliminate some variables and allow you to present the problem to canon more confidently, but it looks like you may need to send that back to be worked on.
 
zimpff said:
what could i be doing wrong? given that i am using f11 the focus should still hit something sharp on the main object?
Click to expand...
Maybe a stupid question: Is the rear lens element clean?

or... did you drop the lens (even within a bag) anytime in the past?
 
hey, good points. but none of that applies. i looked yesterday night and the lens is clean and i never dropped it. how long does it usually take for canon to fix a lens?
Canonite1 said:
Canonite1 said:
what could i be doing wrong? given that i am using f11 the focus should still hit something sharp on the main object?
Click to expand...
Maybe a stupid question: Is the rear lens element clean?

or... did you drop the lens (even within a bag) anytime in the past?
Click to expand...
 
what type of things should i try? like focusing on different distances and then taking pictures with various apertures? the problem is that i have the feeling now when i look closely that it is always pretty blurry. could somebody upload a few sample 28mm shots?
xtoph said:
it is hard to tell what exactly might be causing the softness, but
it is easy to tell that it is there and it shouldn't be. you might
want to run some more controlled tests (with a tripod and mirror
lockup and good light, and not too close to the camera) to
eliminate some variables and allow you to present the problem to
canon more confidently, but it looks like you may need to send that
back to be worked on.
Click to expand...
 
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