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Checking Lens Sharpness

Discussion in 'General Discussion' started by midocr, May 15, 2011.

  1. midocr

    midocr

    Mar 28, 2008
    OH - IO
    Mike
    I need some recommendations for how to test the sharpness of a lens. I have several lenses in the same focal range and am trying to decide which to keep. I want to keep the sharpest of them. I've done arbitrary tests and can't come up with a definitive winner. I'm not talking about AF accuracy. I can make that adjustment in camera if it's needed. How is the best way to test a lens for sharpness?
     
  2. ejstefl

    ejstefl

    385
    Jan 13, 2011
    Milwaukee, WI
    I've never done this, but tape some newspaper on the wall, throw the camera on a tripod, and shoot the newspaper. After that you can examine it at 100% to see. Also a good way to test what apertures are the sharpest on a given lens.
     
  3. midocr

    midocr

    Mar 28, 2008
    OH - IO
    Mike
    I've tried shooting print but I don't think print itself is sharp enough to tell minute differences in the image. Most print on paper bleeds and is not very sharp itself.

    I've looked at several youtube tutorials and am going to try some of those. I just respect the opinions of the people here more than youtube.
     
    Last edited by a moderator: May 15, 2011
  4. I rarely test lenses unless I am experiencing an issue in my shots, so I can't recommend a technique. There are several factors in lens performance in addition to sharpness. Many of the cataloging programs (including Lightroom) will allow you to create collections of shots taken with the same lens. I suggest looking at the images you have taken with each of the lenses in question and picking the one that produces the results you like most.
     
    Last edited by a moderator: May 15, 2011
  5. RWBlue01

    RWBlue01

    773
    Oct 20, 2010
    home
    I get most ****** off about sharpness when taking pictures of flowers. They have enough detail that when I get it right, I know and when I don't, I know.

    So if I was testing lenses, I would get some flowers to test against.

    An orange may also work, but I just don't know.
     
  6. midocr

    midocr

    Mar 28, 2008
    OH - IO
    Mike
    That's the problem. I can get good images from all the lenses. Every now and then I'll get a really good, sharp one. So there doesn't seem to be a pattern to this. I shoot a variety of conditions both handheld and with a tripod. I think I just need to set up some type of controlled test to figure out if one is sharper than the other. Just haven' come up with a definitive method yet.
     
  7. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    Brick wall at a distance. Make sure sensor is square to the wall.

    This may sound odd but you can also compare file sizes when shooting the same subject. The image with more detail will compress less.

    You can use Imatest, but be warned that shooting targets requires a precise and consistent setup to produce results that are reliable. Most people will not go far enough to maintain such a setup.
     
  8. Lurker

    Lurker

    Jul 21, 2007
    NJ
    Seriously, if they're that close together why worry about which one is the sharpest? Instead I would worry about other things like AF accuracy, speed, build quality, etc.
     
  9. midocr

    midocr

    Mar 28, 2008
    OH - IO
    Mike
    Yea, I understand that.

    True.

    To clarify, the lenses I'm testing are Nikkor 24-120 F3.5-5.6 VR, 18-200 F3.5-5.6 VR, and the Tamron SP 24-135 F3.5-5.6. Of the three, the Tamron probably has the reputation of being the sharpest. It does not have VR, which I find helps when hand holding.
     
  10. How often do you enlarge to 20x30? At 8x11 I doubt it if you will be able to notice a significant difference among the lenses you are concerned about.
    If you are using DX bodies you should do very well with your 18-200 VR, unless you do not have use for a wide angle. The 18-200 VR is a very practical all around lens and although slightly soft at 200mm toward the larger openings unless you have a critical eye and you are looking at a big enlargement I do not believe you will see the differences in the resolution of details.
    Of those three lenses use the one that better fit your photography and do not agonize on them about sharpness.
    By the way, I have seen awesome enlargements from that 18-200 VR.

    William Rodriguez
    Miami, Florida.
     
  11. Lurker

    Lurker

    Jul 21, 2007
    NJ
    With superzooms like that I would look, as William mentions, into corner sharpness and purple fringing. That's the weak spot of any zoom lens and usually the larger the zoom range the weaker the lens gets.
    Shoot some high contrast shots (tree leafs against the sky for instance) and pixel-peep to see how they're dealing with that. Purple fringing is fairly good to correct in post processing though. If the 18-200 doesn't come out that much worse than the others you might want to keep it given its wider zoom range.

    For fairness you should compare all three lenses at the 24-120 range though. The 18-200 might be softer at 200mm but the others don't offer that - so see how it compares at 120mm (and the same for the wide end of the range)
     
  12. I would do this far less scientifically than everyone else here is suggesting. I would go through your photos, and decide which of these lenses has produced the most keepers. Keep that one, and sell the others.

    How sharp a lens is viewed on a monitor at 100 percent or greater is largely academic. Photography can be after all an art form, and for some photographers certain lenses have a certain... feel to them.
     
  13. Which body are you using?

    I only ask because I used the AF Fine-tuning on my D7000. Then I upped the in-camera sharpening and my shots started to pop like I expected.
     
  14. midocr

    midocr

    Mar 28, 2008
    OH - IO
    Mike
    D300. I've checked focus on all three and they are pretty much dead on. I may have to play with the sharpening in the pic controls to see if that gives me more of what I'm looking for.

    I might try to set something up this afternoon and run some tests. I'll post comparative images if I do.
     
  15. midocr

    midocr

    Mar 28, 2008
    OH - IO
    Mike
    How do you mean?
    So true. I shoot with a gentleman who has made living at it for years. Very technically perfect photographer, but his end resulting images look more like fine art paintings. That's what he's trying to achieve.
     
  16. Unless you have another lens to cover the wide end the 18-200 is the logical choice. 24mm is not nearly wide enough on DX IMO.
     
  17. The sharpness/IQ/technique required to make a sharp looking 12X18 or even just a sharp looking internet sized file is not the same thing as the sharpness required for a shot to look good viewed at 100 percent on a monitor. Prints, even large ones like 12X18 (and to an extent, sometimes even larger) will hide flaws. It's a lot of technical mumbo jumbo but viewing your shots at 100 percent is like viewing your shot enlarged to mural size from 2 feet away. Many of my shots simply will not stand up to 100 percent pixel peeping simply because I refuse to religiously adhere to hyperfocal rules. I'd rather have something slightly less sharp in the frame than move back 2 feet and change my vision of the scene. Plus having one part of the frame slightly sharper than the rest can draw the viewer in. It's something that has to be practiced and you have to be aware of it at all times but it can work quite well. Simply put when art is the goal perfect, lab sharp photos are not always necessary. So long as there are no technical problems with any of these lenses they are all 'sharp enough' for you to create art.

    Unless of course stock photography is your goal, then you have to find the sharpest one of them all. The reason everything has to be perfect within the frame for stock is because the client my only want to use 20 percent of the picture for his ad. If the 20 percent he chooses to use isn't sharp then it's useless to him.
     
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