Canon EF 70-200mm f/4L USM Sharpness Test (Warning: Extensive Photo Samples)

Discussion in 'Beyond the Basics' started by jamesino, Aug 21, 2008.

  1. jamesino

    jamesino TPF Noob!

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    I purchased a canon ef 70-200mm f/4l (non-is) a few weeks ago and have been getting somewhat inconsistent results with the pictures.

    I have a Canon Rebel XTi (400D) and am shooting with no filters, no teleconverters, no extension tubes- only a lens hood.

    The following photos were all taken in RAW and converted in JPEGs, however, no post-processing was done in ACR. I just opened up the file in ACR and clicked "Open file" and saved it as a maximum JPEG. The photos were uploaded onto Freewebs and were not optimized for web. The photos uploaded look nearly identical/identical to the ones on my computer. All shots were taken using Partial Metering, and only the Central AF point was selected and the picture recomposed.

    These group of photos were taken about an hour before sunset. White balance was set to daylight. The embedded photos are all a 100%, 600 x 600 crop of the focal point and usually around the center frame. The link to the full, uncropped image is provided below the crop as a link.

    Pic 1
    ISO 100, f/4, 70mm, 1/640s

    [​IMG]

    Full, uncropped image (4mb): http://www.freewebs.com/olumak/sample1.jpg

    Pic 2
    ISO 100, f/4, 200mm, 1/800s

    [​IMG]

    http://www.freewebs.com/olumak/sample2.jpg

    Pic 3
    ISO 100, f/4, 70mm, 1/400s

    [​IMG]

    http://www.freewebs.com/olumak/sample3.jpg

    Pic 4
    ISO 400, f/4, 100mm, 1/160s

    [​IMG]

    http://www.freewebs.com/olumak/sample4.jpg

    Pic 5
    ISO 100, f/4, 149mm, 1/320s

    [​IMG]

    http://www.freewebs.com/olumak/sample5.jpg

    This picture was taken indoors. The camera was rested on a coffee table and a 3 second countdown paired with an MLU was initiated.

    Pic 5
    ISO 100, f/4, 200mm, 1/30s

    [​IMG]

    All of the above pictures I think are very sharp and are fine. But occasionally, I get pictures like these:

    These were taken during midday. Several shots were taken and all of them turned out this way.

    Pic 6
    ISO 100, f/4, 200mm, 1/800s

    [​IMG]

    http://www.freewebs.com/olumak/fly.jpg

    Pic 7
    ISO 100, f/4l, 200mm, 1/800s

    [​IMG]

    http://www.freewebs.com/olumak/leaf.jpg

    While this lens does produce nice results when it is working properly, I do not see too much of a difference when compared against the kit EF 17-55mm lens:

    Pic 8
    ISO 100, f/5.6, 55mm, 1/200s (camera-mounted flash used)

    [​IMG]

    http://www.freewebs.com/olumak/emma.jpg

    I acknowledge the fact that this last picture used flash, while the other did not; but does it really make that much of a difference?

    Thanks.
     
    Last edited: Aug 21, 2008
  2. Montana

    Montana TPF Noob!

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    Pic 4 and 5 of the girl would not be acceptable sharpness to me. Are you shooting from a tripod? Since it is hit and miss, I would lean to user error rather than a lens issue. How close were you to the fly and the leaf (?) ? That lens doesn't have a real close focus ability. Minimum focusing distance is 3.9ft.

    Derrick
     
  3. jamesino

    jamesino TPF Noob!

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    No they shots are all hand held, but I don't think the pictures display any signs of camera blur or motion shake.

    Pictures 4 and 5 were shots from quite a distance back than the previous pictures. You can use the size of the eyes are a reference. I've noticed that the image quality begins to drop off drastically as the focal distance (distance between me and the subject) increases.

    As for the fly and the leaf, both were shot from about 2m away. The 70-200mm has a min. focal distance of 1.2m and the AF point was able to confirm a proper focus.
     
  4. RyanLilly

    RyanLilly No longer a newbie, moving up!

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    This is a simple Depth of field issue. When shooting from 2 meters at f/4 and 200mm, DOF is less than an inch, so even though you focused correctly, even the slightest breeze will put you out of focus. That is why you missed focus on the leaf and fly. At those distances a tripod is a must
     
  5. davebmck

    davebmck TPF Noob!

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    Picture 5 is taken at 200 mm and is sharp. I noted that the camera is fixed here. So it doesn't seem to be a problem at the longer focal length. I agree with RyanLilly, it seems to be a DOF problem. At shallow DOF, when you are hand holding, you can move ever so slightly forward or backward and be out of focus.

    BTW, picture states it is at 55mm. How did you get that with a 70-200mm?
     
  6. jamesino

    jamesino TPF Noob!

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    Picture 8 was at 55mm, slightly above the picture you'll note that it was taken with the kit 17-55mm lens. The sharpness appears to be comparable to the 70-200mm.

    While the DOF issue certainly seems possible, the pictures were taken with me sitting on my porch with my elbows rested on my knees. I think one inch should be enough leeway to get the picture in focus.
     
  7. usayit

    usayit No longer a newbie, moving up!

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    200mm @ f/4 with the subject 10 feet away (i'm just guessing at subject distance) gives you a DOF of 1.32 inches.
    DOF is more likely the problem. Try shooting on a sturdy tripod to rule out the lens.

    So why do people praise handheld 200mm @ f/2.8 again?
     
  8. jamesino

    jamesino TPF Noob!

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    Oh ok thanks. What about Pic 5? I've noticed that if I'm close enough to fill the frame with someone's face, the facial features will be quite sharp. However, from far away, say roughly 10-20m, the image quality drops down significantly, which is upsetting given that this is a telephoto lens.
     
  9. usayit

    usayit No longer a newbie, moving up!

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    Do yourself a favor... mount on a tripod and take a test photo. There are so many variables asking what went wrong in pic 5 is all speculation. To be honest.... it looks sharp enough but no one can tell with Jpegs.

    Also.. you are doing yourself a disservice if you start to crop a small area and ask why isn't it sharp... Your crop is even more than the typical 100%
     
  10. jamesino

    jamesino TPF Noob!

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    I will be sure to try that when the sun is up.

    In the meantime, I used an online DOF calculator to calculate the DOF for a picture taken at 200mm, f/4 at 1.2m away and it gave me 5mm (millimetres) as the total DOF; is this possible? I had no idea that the DOF was that shallow.
     
  11. usayit

    usayit No longer a newbie, moving up!

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    Yes... www.dofmaster.com if you haven't already run into it yet.

    This is the number one reason why there is such a misunderstanding about shooting wide open in natural lighting. Those that use wide aperture as the end all solution without considering the ramifications or other possibilities are generally working off online/read knowledge rather than working knowledge. As you discovered through your experimentation...

    I love shooting with a 50mm f/1..... getting the DOF just right is part of the game.... not the source of frustration (once you understand the difficulty/limitations).

    ISO, aperture, shutter... its a balancing act.
     
  12. jamesino

    jamesino TPF Noob!

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    Ok, these two shots were taken around 2pm. The camera was rested on a porch handrail, which is more stable than a tripod, and a 3 second countdown with an MLU was initiated.

    Pic 9
    ISO 100, f/4, 188mm, 1/250s

    [​IMG]

    http://www.freewebs.com/olumak/sample6.jpg

    Pic 10
    ISO 100, f/4, 200mm, 1/250s

    [​IMG]

    http://www.freewebs.com/olumak/sample7.jpg

    Please note the link underneath each 100% crop links to the full-resolution, uncropped image- 4mb.

    There is a marked degradation in image quality and sharpness as the subjects move farther away. These shots were all taken from about 8m (roughly 24 feet) away on a windless day.
     

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