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Old Dec 5, 2008, 2:31 PM   #1
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This is a topic that's been discussed at length, so I'm looking for advice here for what to do next rather than a proclamation that there isn't or is a problem.

I just got a Rebel XSi from B&H yesterday. Three lenses -- 50/1.8 II, 70-200 f4 IS, and 17-55 f2.8 IS. I was playing around with the prime yesterday, trying to learn the camera settings, and wanted to verify that the AF was working correctly. As far as I can tell, it's not quite right. Examples and descriptions of how I took the photos are below. (Ignore the subjects and composition -- this was for testing only after I began to have doubts!)

All photos were shot in AF and with the center AF point only. One-shot AF. All were shot through viewfinder (not Live View). All shot with the 50/1.8. Tried shooting in low-light on tripod (6s exposure, f5.6, ISO100) on the 70-200 with mirror locked up but similar results... out of focus subjects (subjects were a countertop and a wall calendar).

Shot with JPEG (planning to shoot RAW once a larger memory card gets here), but I wouldn't have expected this much softness (see first set of images -- ceiling fan), even with JPEG. I also tried boosting sharpness to maximum, but the effects were negligible.

Let me know if you can't see the EXIF information.

Any suggestions?

****

Image 1: ceiling fan (not sharp)
http://netfiles.uiuc.edu/xwang22/Pho...0unfocused.JPG

Image 2: ceiling fan (sharp)
http://netfiles.uiuc.edu/xwang22/Pho...%20focused.JPG

Focused on the root of the blade (where the blade meets the motor, more or less). Slightly different apertures, but should be stopped down enough not to have affected the results this much -- I would think. (names got mixed up... sorry)

****

Image 3: cable box (not sharp)
http://netfiles.uiuc.edu/xwang22/Pho...0unfocused.JPG

Image 4: cable box (sharp)
http://netfiles.uiuc.edu/xwang22/Pho...%20focused.JPG

Focused on "interactive digital communications" letters. Same (exact) settings for both shots -- one focused, one did not.

****

Image 5: panel van (AF)
http://netfiles.uiuc.edu/xwang22/Pho...%20--%20AF.JPG

Image 6: panel van (manual focus)
http://netfiles.uiuc.edu/xwang22/Pho...%20--%20MF.JPG
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Old Dec 6, 2008, 3:14 AM   #2
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What you need to do next is some proper focus tests. Google has many links to tell you how to do this properly.

Get some charts, sort out the lighting, set up a tripod and do it again.
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Old Dec 6, 2008, 12:26 PM   #3
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peripatetic, thanks for your reply. I don't have a good way to obtain proper lighting, so for now, I'm relegated to rely on a tripod. It's cold and wet outside, and in case I do need to get an RMA for this, I don't want to get any unnecessary splatters yet...

A few focus tests -- I used an incandescent table lamp above the desk, but there was some (minimal) ambient lighting and some (more) overhead light from CFLs.

IS was off on all four tests, I cranked up JPEG sharpening to full (I did, anyhow, before I got an ERR 99, but an off-on reboot solved that. I didn't double-check to see if the reboot undid my settings).

Auto-focus was was center point; manual focus was through 10x LV with the LV mode set to Live View (rather than quick). Taken at an approximate 45° angle (angle between camera lens and subject plane) on a tripod. Mirror lock-up enabled.

***

Ruler test: center AF point was set to the 6" mark.

Ruler test -- AF
https://netfiles.uiuc.edu/xwang22/Ph...%20--%20AF.JPG

Ruler test -- MF through 10x LV
https://netfiles.uiuc.edu/xwang22/Ph...%20--%20MF.JPG

***

Nikon D70 focus test page: focused on as the instructions said... on the black line in the center of the page.

Focus test -- AF
https://netfiles.uiuc.edu/xwang22/Ph...%20--%20AF.JPG

Focus test -- MF
https://netfiles.uiuc.edu/xwang22/Ph...%20--%20MF.JPG
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Old Dec 6, 2008, 5:38 PM   #4
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tiger,

Its very normal for new Xsi owners to think that their focus isn't sharp - especially if your used to lower end cameras that tend to apply excessive sharpness to shots.

There is a custom setting in your camera where you can increase the sharpness a little.

It's really just a matter of getting used to a cam with a little "softer" image output, or just go in and tweak the camera sharpness setting.

Probably nothing wrong with your cam. Just post a photo or two here and we'll take a look.
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Old Dec 6, 2008, 5:57 PM   #5
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Thanks for the reply, Terry -- there are images posted (the links in my posts are posts to what I'm referring to).

The focus tests from the previous post, in my opinion, are the most telling.

This doesn't have much to do with sharpness (I cranked up the in-camera sharpening all the way), unless the focus tests suggest otherwise (in my world of misunderstandings).
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Old Dec 6, 2008, 6:01 PM   #6
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well, low light tests are a poor guage.

Just get out there on a sunny day and crank a few photos and post them.

it would be pretty obvious if we looked at those shots.

More than likely, you don't have a problem so don't lose any sleep.
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Old Dec 6, 2008, 6:11 PM   #7
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Well, it looks like that lens is front-focussing a bit. But that may just be a factor of operating in such low light. With those light values it's possible the camera is actually within spec.

Whether it's worth getting it calibrated or not for a $100 lens I don't know.

Make sure you check all your lenses, because if it's just the 50 then I'd try to swap it.
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Old Dec 6, 2008, 6:27 PM   #8
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Makes sense. I will be calling B&H tomorrow (they have a two business day limit on "damaged" goods, so I want to see if they want to treat this as "damaged" lest I forfeit that route entirely), but do plan to grab some images in better light.

peripatetic wrote:
Quote:
Well, it looks like that lens is front-focussing a bit. But that may just be a factor of operating in such low light. With those light values it's possible the camera is actually within spec.

Whether it's worth getting it calibrated or not for a $100 lens I don't know.

Make sure you check all your lenses, because if it's just the 50 then I'd try to swap it.
Abut the light: this is true, so I'll try to get a better representation once I get better lighting.

The focus tests (I see that I forgot to note it) were done with the 17-55 mm f2.8, not with the 50 mm prime. Given that I've gotten odd focusing with all three lenses now, I'm not sure that the 50 mm 1.8 was that far off.

Do I send in all three lenses for calibration (if I go that route) or just one?
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Old Dec 7, 2008, 5:01 AM   #9
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If all 3 lenses exhibit essentially the same front focus behaviour then your camera is out of calibration.

It depends then on how you want to approach it, either you could try to get the whole lot calibrated (which is easily done at the service centre, but you will be without your gear for a couple of weeks), or alternatively ask B&H for a new camera. As you have just purchased it I would be tempted to go for a replacement and hope the next one is better calibrated.
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Old Dec 7, 2008, 1:41 PM   #10
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Pure autofocus outdoors today with the 17-55 gave me mixed results. The shots were mostly of brick buildings, with a few of grain-looking-like plants. Some shots were beautifully crisp, others were just barely out of focus.

Can someone tell me whether the following two images were MF or AF?

http://netfiles.uiuc.edu/xwang22/Pho...lding%201.JPG;
http://netfiles.uiuc.edu/xwang22/Pho...lding%202.JPG;

Did some shooting with the 70-200 and results were pretty good, but is it true that at longer focal lengths, the effects of missed focus are less pronounced? The 70-200 focus tests were almost bang on... I'm not sure if this is because I wasn't shooting at a 45° angle or if the camera is amazingly calibrated with the 70-200.

The interesting thing is that the first calendar shots (wall calendar) I took with the 70-200 weren't in focus, but the focus tests were good, but the 17-55 had great calendar shots but poor focus tests.

Maybe it's just me, after all?
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