fuzzy focus

About 2 weeks ago, I bought EF300mm F4 IS from BHphoto. I tested and found that

the lens has some problems (very fuzzy at F4), so I returned the lens for refund

and got EF70-200F4 IS. It arrived yesterday but again it has same issue. It is

acceptable at 70mm side, but unusable at 200mm F4 and needed to stop down to F16

to get OK result (this lens should produce excellent result on 200mm side even

with aperture wide open). I'm thinking about returning this lens again.

 

This is not the first time I had this type of issue, I had same issue when I

bought 50mmF1.4 and 70-200mmF2.8IS. And also this is not just me but many of my

friends(it is very common among 70-200mmF2.8IS, but even with 85mmF1.2) The only

canon lens I have that I didn't have to send back was EF135mmF2. This certainly

makes me wonder how many sub-standard lenses out there. It seems the lenses

with IS are more likely to have QC problem.

 

Is there any good way to avoid this type of issue?<div></div>

Are you sure your camera isn't out of adjustment?

 

There are many, many DSLR users who have never had this problem (me included).

 

Either you have really, really bad luck or something else is wrong.

 

Anyone can get a bad lens, and the really unlucky might get two bad lenses, but all bad lenses? Very unlikely.

 

My informal lens survey (http://www.lensplay.com/lenses/lens_defect_results.php) suggests that overall you should be seeing about 1 defective lens in 15 for Canon/Nikon/Minolta lenses, averaged over all lenses (cheap to expensive). I'd have thought that "L" lenses would be even lower in defects.

 

Defect rates on 3rd party lenses are a bit higher. Maybe around 1 in 9 for Tokina/Tamron and 1 in 5 for Sigma.

Pardon me if you already know any of this, but perhaps these are some things you have

not noticed or considered.

 

Your sample photo looks like it shows camera shake in the vertical dimension. Was this

hand held?

 

If you are relying on IS, you need to half-depress the shutter button for a half-second or

longer to give the IS time to stabilize the image. If you just press the shutter release

without doing this the IS will not work.

 

Shooting at f/16 will give you less than optimum focus. Your sharpest focus (assuming a

crop sensor body like the 30D, etc.) will likely be around f/8. At f/16 defraction begins to

degrade the sharpness of the image.

 

You don't say in your message, but is this a 100% crop? And is it RAW or in-camera jpg? If

it is a 100% crop of a RAW file, you should not expect it to be extremely sharp. No in-

camera sharpenin is applied to RAW images. You need to apply sharpening in post

processing - and doing so can give you a rather sharp image.

 

If this is a crop, is it from the center of the frame or the edges? Did the AF indicator light

up on the portion of the scene shown here, or was it detecting some other point within the

scene?

 

Forgive me for the implication fo what I'm going to write next. However, if you are

encountering the same focus problem with a whole string of normally excellent lenses

(70-200 f/2.8 IS, 85mm f/1.2, 300mm f/4, 50mm f/1.4) there are only a few realistic

explanations. One is that Canon is a lousy lens manufacturer - but that is not the

reputation that Canon has with these particular lenses. Another is that you have

astonishingly bad luck and/or a dealer who sells crappy copies of lenses. Not likely with

B&H. Another possibility is that there is something in your technique with this particular

equipment that is leading to consistently out of focus results.

 

Take care, and good luck solving this.

 

Dan

I agree with the other posters -- that many bad lenses is improbable or else a lot more of us would be complaining far more than we do. Not just here but all over the web at a variety of photographic cites. For confirmation, you might want to check the user ratings of the lenses you have problems with at the user review section of sites like fredmiranda.com.

 

The photo you posted is inherently difficult because its not clear whether the screen in front or the object in the background is the intended target. But that may not be relevant if you have a lot of other bad examples of different subjects.

 

One question that comes to mind is whether the problem occurs only in autofocus? Can you manually focus sharper than the autofocus works? Also do you observe the problem at particular apertures, or over all apertures? In general, the more information you provide, the more feedback you will get.

If you used all these lenses with the same body, then that's your problem. Something isn't communicating properly with something else.

 

Those lenses you mentioned are some of the most highly regarded in the Canon lineup, and the odds are huge that they would all have the same problem

Thanks for the quick response!

 

The images posted is RAW and center crop. It looks like double-line-blur(nisen-bokeh) usually happen in the blurred background due to overcorrected spherical aberration, I don't know why it is showing at the area of critical focus though. The hand blur usually show sharp core in the streak(not fuzzy like this). And also, the quality should get worse at F16.

 

The first I though about the camera calibration (I had mid range focus issue with my 5D and couldn't get sharp focus at range between the last number on the distance indicator to infinity, so I had to send it back to Canon), but if that was the issue then all my lens should show the same problem. 35mmF1.4, 50mmF1.4 and 135mmF2 work just fine.

 

100% crop of the same area shown above taken with 135mm F2 @f5.6, 1/800

http://www.flickr.com/photos/type665/393433518/

 

I wish I could send my lens for testing.

http://www.photozone.de/8Reviews/index.html

 

I know I usually buy items from BH and I never had any problem with other products.<div></div>

Hi,

 

Another possibility in addition to those mentioned... if using any of the digital bodies, there are sharpness settings in many of them. These can be "turned off", most especially in RAW capture. It's then up to the RAW converter to apply some sharpening, whether that's done in camera or in your computer. Otherwise, a crop of part of the image might easily end up like the sample you show. Most digital cameras deliberately blur the image to prevent moire and other issues, then rely on resharpening the image in camera or later in computer.

 

I agree, highly unlikely you would have problems with so many lenses. I've got 13 or 14 Canon EF lenses, including some that you mention, that have been used over the years on 5 or 6 different camera bodies. I've never had to return even one lens for any problem like you show. SO, I'm inclined to believe it's some other factor: most likely a problem that is common to all the different lenses, such as something in the camera body (misaligned sensor, focus mechanism out of adjustment) or user error.

 

Another possibility.... If the sample is a cropped area from an image, how large was the original? There is a practical limit to enlargement and digital captures seem to be more sensitive to enlargement than film. (I.e., seems like digital have less potential for enlargement beyond their native resolution, without some special handling). A really small crop from an image might look like the above, no matter what's done. In general, I suspect folks are much more critical of their camera equipment today, since they can view the images on a decent quality computer monitor and really zoom in to huge magnifications. Fine errors that would never have mattered in the past, with enlargements from film to print, now seem to jump off the monitor at us.

 

Keep us posted!

The picture above is wrong picture<div></div>

Kazuaki,

 

Is there any chance for you to try these lenses on one of your friends' body?

 

Try to shoot a static object on a tripod?

 

Try to manual focus and compare to the AF ones?

 

Try some compositions with the same settings and same lens on 2 different bodies?

 

For once, try the green rectangle mode on a tripod?

 

If all these tests give you bad results and then you'll know what's wrong

Forgot to ask:

 

What was your focus point on the flag picx? Was that handheld?

 

F4 is quite a shallow DOF at 200mm. The 1/2500 speed will freeze the action in the focus plan only, not the out of focus zone.

I usually test on all 3 bodies I have, but just in case I borrowed Xti from my friend. The results are the same, 200mm side has issue. I also did focus bracketing to see how the fuzziness will change, and found that the double line show even at the critical focus. It seems like put another layer on top of existing image with 10% opacity(with fuzziness). The other thing I noticed was that the image quality is bit better with IS off even at 1/400. 70mm side is OK (I can get good result even at 1/5 with IS handheld). All reviews and even Canon's MTF show excellent result on this lens especially on 200mm side, so I certainly expect the resolution to be better than $100 sigma on my Nikon.

<p>There are too many variables here. It might be helpful to rule things out in steps:

 

<ol>

<li>To start, put the camera on a tripod, use mirror lockup and a remote shutter release,

turn off IS, use f/8, and take a photo of a well-lit flat high contrast subject such a a wall,

etc.</li>

<li>If the result is not sharp try to manually focus - if nothing else try a little closer and a

little further and note if there is any difference. If either improves the image you may have

an AF problem.</li>

<li>If the result <i>is</i> sharp try the same experiment as #1 with IS turned on. If it is

still very sharp your IS is likely functioning correctly. (I'm not certain, but you may have to

turn MLU off on some bodies to get IS to function. If so, use a high enough shutter speed

to virtually eliminate mirror slap as an issue.) If there is a <i>significant</i> difference

you might, I suppose, have some sort of problem with IS... on all your lenses... Keep in

mind that some claim that IS will make the image <i>slightly</i> less sharp.</li>

<li>If you get a sharp photo with IS on and the camera on the tripod with MLU and a

remote shutter release, you have pretty much ruled out a bad lens, bad AF, or bad IS.</li>

<li>Remove the camera from the tripod. Turn IS on, MLU off, and don't use the remote

release. Try to shoot at a relatively fast shutter speed - like 1/focal length or faster. Press

the shutter half way, wait for a full second for IS to fully engage, then carefully press the

shutter the rest of the way.</li>

<li>If you cannot get a sharp image in the previous step then something may be up with

your technique. If you do get a sharp image this way, then it would appear that your

system is working correctly and the previous issues were due to something you did while

taking the photos.</li>

</ol>

 

Beyond that, I can't imagine what could be going on.

Thanks Dan for the detailed advice. It didn't pass the test #2, I can't get clear image even with focus bracketing, I took 16 shots with slightly different focus setting. The test clearly shows peak focus and even at the peak the image has some fuzziness. It is very prominent at 200mm side, and 70mm side it is visible but not as prominent as 200mm side. And the fuzziness gets worsen as the focus distance gets near the infinity mark.

 

I also found another problem, the tripod detection occasionally fail.

 

I'm not a tester, I should be spending more time for shooting rather than testing lenses. Does anyone know the site like this in the US?

http://www.photozone.de/8Reviews/index.html

They don't take request from outside the EU. :-(

 

I'll probably return this lens on Monday for refund and instead of getting another one from BH, just go to the local camera store and do the test on the lens that I'm getting before I commit to buy a particular sample.

The test picture of the flag appears to have an issue with motion blur. The shutter speed is quite high to freeze almost any motion.

 

Have you tried to take pictures with IS turned off?

I did try IS off, and the results were tiny bit better. I suspected IS as well, my assumption was IS is shifting the image at the moment of exposure. If the fuzziness is caused by motion blur, this is the only probable explanation. I take picture for local hockey team, and even at 1/500 you can freeze flying pack.

 

http://www.flickr.com/photos/type665/357378136/

 

Minimum shutter speed for 200mm lens is around 1/200 (1/300 ~1/400 for APS-C body), and if you are shooting at 1/2500 it is quite rare to get any motion blur at all(unless you are intentionally swinging your camera). You can stop splashing water at this shutter speed.

 

http://www.flickr.com/photos/type665/356632660/

 

Only reasonable explanations are either misaligned element in the lens is causing double-line-blur like effect, or IS is shifting the image while curtain is open (shifting at much faster speed than you swing your camera). But if any misaligned element is causing the issue turning IS off will not affect the image quality, so it is more likely that the both IS motion and the lens element (possibly IS element itself) are causing the issue.