Please provide feedback on these Sigma 30mm photos

Discussion in 'Digital Photography' started by Eauboy, Mar 25, 2008.

  1. Eauboy macrumors regular

    Eauboy

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    #1
    I recently purchased the Sigma 30mm f/1.4 lens for my Nikon D80. As a bit of background, reports on this lens are mixed. A significant portion of reviews mention a 'front focus' problem with this lens. Everybody else seems to rave about it. I'm really having a hard time with this lens and I'd like some feedback on a few samples that I have posted:

    http://picasaweb.google.com/greg.pickens/SigmaTest

    In short, I'm trying to decide whether or not to keep the Sigma. I bought it for its short focal length and wide aperture, but if it won't behave with autofocus then I'll never get much use out of it. I can only keep it for one or two more days before I have to return it. I'm open to better/more testing suggestions.

    Any photo tagged as 30mm is the Sigma. The photos tagged 60mm are from my Nikkor 60 Micro, which I consider to be a sharp lens. All are autofocus shots in moderate to strong light. The camera is set to AF-A focusing. I shot aperture priority on all shots, with 'single area/normal zone' selected for autofocus.

    The text crop of the REI ad is from a setup I made this afternoon to try to fairly compare the two lenses. Due to the focal length difference I had to re-do the setup between lenses, so it isn't a perfect comparison. I see a profound difference between the Sigma and the Nikkor at the same aperture (2.8, the lowest the Nikkor goes).

    The Spongebob photo I took to showcase the soft focus issue I think that I am seeing. On the photo where Spongebob is parallel to the focal plane nothing seems in particularly sharp focus to me. In the example where I shot him at an angle, some portion (more to our right) does seem to be in focus. Those shots were at a very wide aperture, but I'd still expect a flat image to be in better focus than I saw with the flat-on photo. The REI ad doesn't seem to be TOO bad, but when compared to the Nikkor you still see a pretty profound difference in sharpness/contrast (focus?).

    The cat photos are with the Sigma and Nikkor, both at f/5. Hard to compare of course since the cat is always on the move. The Sigma certainly doesn't look so bad here.

    The flower doesn't look too bad either, but that's at f8. What I don't show in the gallery are any people shots. I took several of a friend and self-shots of myself. None of them looked sharp to me, but perhaps my expectations are too high for wide-open operation.

    Finally, check out the distinct lack of sharpness on the presidential seal photo. That's a raised emblem, and I couldn't get it any sharper than that in five tries.
     
  2. Abstract macrumors Penryn

    Abstract

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    #2
    Maybe your copy of the lens DOES have a problem. You don't need to return it. Just send it to Sigma to be calibrated, and they'll sort this issue out for you.

    Mine is great, and works well. Actually, I bought it and didn't use it often, but over the past month, I've been using it very often. It hasn't left my camera.

    EDIT TO ADD: I don't really see why you'd return it for something that's fixable. I'd understand this more if you didn't like the focal length of the lens, but I feel this lens is very useful. You just need to be careful with focus and nail it when you're using the lens at f/1.4 or f/2, since the depth of field will be very very small. If you take a portrait photo, focus on the eyes of the subject.

    Here are some photos from over the past 7 days, all using the Sigma 30 mm f/1.4. The ice cream photo isn't sharp, but only because I didn't focus on it. The restaurant I took the photo in was quite dark, so I was forced to shoot at f/1.4. No flash. Combine the f/1.4 aperture and close focusing distance, and you get a very short depth of field. I'm still quite happy with the result.
     

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  3. Eauboy thread starter macrumors regular

    Eauboy

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    #3
    Abstract, thanks.

    Your shots all look fine to me. I agree that the 30mm focal length is very useful, but only if it also performs at lower apertures. Did you notice any softness and/or failure to focus perfectly on your low-aperture, relatively-close-up shots? I took some head shots of a friend and none of them were especially sharp, even when I aimed the AF point right on her eye. Very similar to what I saw with my buddy Spongebob.
     
  4. Abstract macrumors Penryn

    Abstract

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    #4
    Sorry, but if you're going to take somewhat close-up shots of a person at f/1.4, they're going to be soft. Either the eyes are sharp and the nose and ears are blurry, or the nose is blurry and the rest of the face is soft.

    You can't blame the lens for physics. ;)
     
  5. Eauboy thread starter macrumors regular

    Eauboy

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    #5
    So, you don't think from looking at the Spongebob and presidential seal photos that something is amiss? It seems like nothing in those photos is in focus. I understand the concept of extremely shallow depth of field (physics) but surely in relatively parallel subjects like a piece of paper it would be able to focus sharply, and that when taking a portrait, at least the part of the subject's face that I focus on (eye) would be sharp.
     
  6. Abstract macrumors Penryn

    Abstract

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    #6
    No, I said you may get soft images if you shoot people/things, even if your lens WAS perfect.

    I suggested that maybe your lens really was "off" a bit, and to email Sigma about it. Their customer service is supposed to be the best. Just email them, and ship the lens off to them for a calibration.

    I'm going to get my Sigma 24-70 mm f/2.8 rechipped for free because it doesn't meter properly at 70 mm. I don't know why the lens has anything to do with the metering, but there you go. Anyway, it's a free fix.
     
  7. Father Jack macrumors 68020

    Father Jack

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    #7
    There certainly is a problem although most occasions where nothing is sharp the culprit usually is camera shake not lens or focus problems .... :eek:
     
  8. SLC Flyfishing Suspended

    SLC Flyfishing

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    #8
    lately I've been doing about 95% of my shooting with a 50 mm f/1.4 lens. I thought it had a problem with front focusing for a while but it was only because I still hadn't grasped entirely just how shallow the Depth of Field is at f/1.4. Trust me, I've gotten shots where only the nose, cheeks, chin and forehead were in focus and everything else was in some sort of disarray. Then I started shooting at f/2.8 or higher for any close-ups and voila, problem solved.

    f/1.4 is handy a lot of the time, but wide open apertures almost never give a lens it's maximum sharpness and the DOF can be a real problem. That's probably most of what you are experiencing. I would e-mail Sigma about getting the lens calibrated though, it will be free and then you can rest assured that it doesn't have a front focus tendency!

    Edit: looking at your gallery, I'm almost certain that you have 2 problems. In the first photo it looks as though the spongebob thing was in focus but you have camera shake making it blurry, I say this because nothing is really in focus and it looks like camera shake is the contributing factor.
    In the second spongebob photo part of him is in focus, but the rest is not, if you look carefully the in focus area is a thin strip running vertically through the image, this is your DOF area. Signifying that in this photo it was just an issue of having a narrow DOF at f/1.4. You'll never get the entire figurine in focus at f/1.4 and that distance unless you shoot perfectly perpendicular to the subject. It also looks like there may be a modest amount of camera shake.

    The photo of the presidential seal looks like there may be some camera shake there too but it's not bad.

    The others look good and sharp to me.

    Work on your hand-holding technique, and google a DOF calculator to get an idea of what you are up against with an aperture such as f/1.4. You will enjoy your lens immensely once you get control over it believe me. I don't think there's anything quite like DOF control for facilitating creativity.

    SLC
     
  9. Abstract macrumors Penryn

    Abstract

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    #9
    He could very well have a valid complaint, though. Sigma's quality control isn't the best. Their lenses that work properly really work well. I love them. However, some of them do come with problems. I don't think this blurring is from camera shake. I think it's from poor focusing by the lens and/or camera.

    Do some more tests, post larger photos here so that we can see sharpness better, and if it's still bad, email Sigma. Take a photo of a 3D object (not Spongebob), and tell us what you focused on.
     
  10. Father Jack macrumors 68020

    Father Jack

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    #10
    Can I suggest using a tripod when doing any tests. There is definitely camera shake in some of your images. As already pointed out by others, Depth of Field at f1.4 is practically nil.
     
  11. Abstract macrumors Penryn

    Abstract

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    But to be fair, he took 2 photos of the writing, and the photos with the 60 mm f/2.8 are sharp, while the 30 mm at f/2.8 isn't. Same shutter speed was used. The depth of field of the 30 mm lens is probably better than that of the 60 mm.

    You could be right that there is camera shake, but I personally believe it is poor focus performance.
     
  12. Father Jack macrumors 68020

    Father Jack

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    #12
    I think this is a case of both of us being correct.

    There is some camera shake evident and this isn't helped by the lack of D of F at such wide apertures.

    You are correct in saying that you have more D of F at 30mm than you do at 60mm.

    The main problem with the Sponge Bob pics is probably caused by either the paper not being parallel to the camera or as you say by poor lens performance. The best way to solve this problem is by running the tests again only this time using a sturdy tripod.

    When carrying out any sort of lens testing a tripod should always be used.
     
  13. Abstract macrumors Penryn

    Abstract

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    #13
    I agree about the paper. I think testing on a piece of paper is just a bad idea unless you're a pro that will take the time to do it perfectly. I don't even know how I'd make sure that the two planes are parallel, nor would I try it. Personally, it's too difficult to do at my home unless the object is far away (so that any slight difference in angle won't matter as much) That's one reason I asked him to pick a 3D object. It's just so much easier to do with any typical 3D object. Pick a Coca-Cola can. You can easily see blur from depth of field on a cylindrical can, along with the sharp, focused parts. Maybe focus on the lettering. I don't know.
     
  14. Eauboy thread starter macrumors regular

    Eauboy

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    #14
    My thanks to everyone who helped me out with this question.

    I decided to keep the lens. After performing a second (or was it third?) set of tests with both the 60mm and the 30mm I saw some of the same issues -almost certainly involving more camera shake than I care to admit- with both lenses. Tests with FAST shutter speeds and/or more careful camera holding revealed that I could under ideal conditions get better results than I had the first time around, but still not reliably at wide apertures. Like several thread contributors, I still believe that a small amount of calibration might help the lens, but it wasn't the main reason I saw problems in my testing.

    I will continue to use the Sigma lens to sharpen my skills with it, and with wide-aperture photography in general. If in the future I decide that calibration would help, then I know what to do. I used the Sigma Friday morning for an opportunity that I knew would require wide angle and some wide aperture. Still evaluating those shots.

    Some FYIs for the test shots that I posted:
    - The REI ad photos were made using a pretty sturdy tripod. The rest were hand-held.
    - I deliberately turned Spongebob at an angle for some shots just to prove (to myself) that there was a least a thin layer of sharpness with the wide-open aperture.

    Thanks again. If I do any more controlled testing I'll be sure to share.
     
  15. pdxflint macrumors 68020

    pdxflint

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    #15
    Just to add a little thought to this discussion: If you're checking/testing the lens wide-open and it's a f/1.4 lens, definitely manually focus the lens, don't rely on autofocus - just to make sure it's really the lens. I think the same thing that applies to macro shots applies here - precise focusing is required as you're looking at the image, intuitively you'll see when you've got the focus where you want it much better than AF can do it. Tripod - manual focus = best results for testing. (Father 'Professor' Jack brought up a great point about the sturdy tripod.)
     

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