Do I have a defective lens???

Discussion in 'Nikon' started by wade_thompson|1, Dec 16, 2015.

  1. [​IMG][​IMG][​IMG][/IMG]Hey you people.
    Been here on the forum for some time.
    I am very frustrated with the sharpness of a used lens I bought a year or so ago and I have tried everything I can possibly think of to get it in sharpness...but simply cannot. I would like your insight and help/
    Lens in question: Nikon DX 17-55 f2.8
    Camera bodies tried on: Two D300s and two D7100... sample bad results.
    Tried AF fine tune in each (-20 all the way up to +20), no consistent better sharpness.
    Only thing I have not tried is adding a filter.
    Here is a typical photo. F2.8 in this case...[​IMG]
     
  2. ShunCheung

    ShunCheung Administrator

    Wade, at least this particular image sample looks fine to me for the 17-55mm/f2.8 DX AF-S wide open @ f2.8 and 50mm. The girl's face and her clothing look sharp. And I opened the full image on PhotoShop to check.
    If you still have doubts, forget about AF fine tune for the time being. Set up the camera on a tripod and use live view to fine tune focus manually and check results. That should eliminate all contribution and issues from AF.
     
  3. This small jpg looks sharp to me. I can see the tiny fuzz on the white vest of the little girl. Have you compared this lens to others you consider adequately sharp? Have you tested with a flat textured surface such as a brick wall and on a tripod? Have you tested in live view? Are you shooting jpg or raw and what type of processing have you done? Wide open is usually the least sharp f stop for most lenses. Have you tested a range of apertures? Lastly, usually when I have a lens I don't like, I just sell it and get another one!
     
  4. I doubt that a filter will help your cause. The small girl (eyes and face) look sharp....tho I'm judging this on a small screen and have no idea how it will render at say 16x20 enlargement. If you wished to have both people in focus, then you'd have to re-position yourself (to catch both on the DOF line) or shoot at larger F-stop to accomplish that.
    I'm not familiar with DX lenses, so I can't make any judgment on that. Having said that, most lenses don't perform all that great at its widest opening....whether the AF is right on the money or off.
    Les
     
  5. ShunCheung

    ShunCheung Administrator

    I should point out that the image of the girl in Wade's opening post is actually 1599.x1536. While it is not full size, it is not that small. As I said, I opened that in PhotoShop to check.
    I also have the 17-55mm/f2.8 AF-S. Its weakness is on the wide, 17mm end. If you use it near 17mm, corner sharpness is somewhat poor and it also has some chromatic aberration.
     
  6. i'm not sure it's reasonable to expect better sharpness than that @2.8. i can see the catchlights in the girl's eyes. there appears to be a little bit of contralight coming from the right of the photo, causing slight overexposure of the girl's hand in the lower middle of the shot, but its effects don't really impact the shot too much overall . also it's hard to get too much detail out of white in bright sunlight wide open, but that is more of a technical thing. looks about the same as results i would expect from nikon 24-70 and other 17-xx 2.8 DX/APS-C lenses i've used. if it doesnt sharpen up by 5.6-f/8, there may be a problem. Also, my understanding is that AF fine tune mainly works to correct front/back-focus issues caused by improper tolerances. It's not a magic sharpening tool for lenses, but rather something which can help align shots if focus is continually missed from where you aimed the focus point. A filter could actually make the lens less-sharp and susceptible to flare, if you get a cheap, non-multicoated one. If you could post a range of shots with the same subject at the same distance from 2.8-f/8 under ideal shooting conditions and base ISO, it would be easier to tell if there's something wrong, but it doesn't look like it based on that one shot.
     
  7. Wade, it seems your flash blew out the highlights (see dark areas on image below). However, this lovely girl's eyes, nose, and smile are nicely sharp at f/2.8.
    If you shot in raw, there is a good possibility you can recover the highlights and see some detail on the hand, hat, and part of the jacket that is blown out.
    Remedy for the future: Enable highlight blinking on Playback, so you will detect blown out areas immediately.
    00ddfF-559783684.jpg
     
  8. I agree with the other posts that the sample image appears adequately sharp. So much of a shooting environment can affect the outcome that its difficult to determine the cause without some testing. If the lens is not performing to your standards then testing is in order. A google search for lens test targets resulted in these two links within the first few hits.
    http://bobatkins.com/photography/technical/testing_lenses.html
    http://www.normankoren.com/Tutorials/MTF5.html
    I use Norman Koren's charts, printed 2 charts per sheet of legal size paper going in opposite directions with several copies attached to 16x20 foam core to check/setup large format rangefinders, focus scales, and ground glass alignment. I printed them on an Epson R2400 at high dpi in advanced B&W mode.
    There are also a verity of test targets available for free download by searching for ' downloadable lens test targets ' that are of high enough resolution for home/studio testing. Print at fine photo or best photo setting on most current printers and a careful setup keeping the camera either perpendicular to the target or at the precise angle for focus point testing and a few test shots will tell you what you want to know about your lens/camera setup. Some tripod/head combinations may introduce vibration into your image also.
    I have a D300, 60mm f2.8 Macro, 2 35-135 f4.5-5.6 AF zooms that are all adequately sharp. The 18-55 f3.5-5.6G VR that came with the body is OK for snapshots and my 75-300 Nikon AF zoom sucks to put it mildly.
     
  9. i didn't look at the EXIF, so i didnt see that flash was used. but that would seem to explain the blown highlights which give the appearance of lack of sharpness. you also have ISO 280 and 1/200 @2.8 on what appears to be a bright sunny day. did you use full power flash here? if so, dialing down the flash to 1/4 or 1/8 should give just enough fill to balance ambient light. the problem with these types of shots is that you are shooting wide open but your shutter is limited to Xsync speed of 1/200. that's probably more light than you need. and you may not have needed flash at all -- cant tell offhand how bright those backgrounds were or if you were shooting directly into the sun.
    in any event, this doesnt seem to be a lens issue, but rather an exposure issue. the background seems far away enough that you probably could have stopped down 1 or 2 stops to f/4 or f/5.6 for increased detail and sharpness and still isolate the subject, which would also mitigate your overpowering flash. or use the flash in manual for fill as noted earlier. you could also use an ND filter if you insist on shooting at 2.8. or put flash into FP mode which reduces overall output but also lets you use faster shutters.
    in general, if there are questions about a lens' sharpness, i wouldnt use a flashed shot to test it, for this exact reason, that the flash can overexpose. in this case, you could have shot the shot, then chimped the playback and flipped on the blinky screen, adjusted your settings, and reshot. hope that helps.
     
  10. Wade,
    i agrre with all the other advises on this post.
    Just one more, if using flash for this kind of shots, get it off camera ( possibly use a flash bracket) and if possible add a diffuser.
    Camera mounted flashes are very portrait unfriendly in most cases, and i this case makes the hair of the child look grey ( and yes if you can see the individual hairs in the fine hair of the girl the picture is sharp..)
     
  11. Do you think the focus issue you are experiencing is due to poor AF or bad optics? Do you ever get really, really sharp images, either with AF or MF?
    For the cost of shipping, you can have Nikon check your lens for you. Should there be an issue, the repair cost would probably be reasonable and would probably be worthwhile doing.
     
  12. The image looks normal for this lens.
     
  13. ShunCheung

    ShunCheung Administrator

    We certainly do not evaluate a lens with just one image, especially since it is a zoom, it is best to capture a number of sample images on both ends of the zoom range, namely 17mm and 55mm and some more in between, at different apertures and different distances.
    The 17-55mm/f2.8 DX AF-S has a similar design objective as the 24-70mm/f2.8 AF-S. These are party, event lenses, mostly used indoors at weddings, etc. They are at their best when the subject is 10, 15 feet away, i.e. around 3 to 5 meters. I find the 17-55 not as good at infinity.
    There is an old saying, if it ain't broke, don't fix it. If there is nothing clearly wrong with a lens, when you send it to Nikon for "repair," it is very much possible that it comes back worse than before.
     
  14. " I have tried everything I can possibly think of to get it in sharpness...but simply cannot. "

    I owned an used this lens for several years for event photography and never had a sharpness problem. Few ever complain about sharpness issues with it. This lens is known for its sharpness So it sounds like the lens is not functioning as it should.

    Having it checked by experts makes sense. After all, who would want to use any lens that does't provide satisfactory image quality for any reason?
     
  15. The little girl's eyes and face look quite sharp to me. There isn't any type of filter that would help with sharpness.
     
  16. it sounds like the lens is not functioning as it should.​
    i dont think there's anything wrong with the lens, based on this particular photo, which has blown highlights from using flash wide open in bright sunlight with a 1/200 shutter. most lenses would perform similarly in this scenario. even so, the lens captured catchlights in the girl's eyes, and the face shows detail and microcontrast. if indeed there is an issue, we would have to see a range of shots at various apertures to correctly diagnose. according to photozone, the 17-55 has excellent center sharpness at 2.8 and peaks at f/4-5.6, where the corners pick up. but from where i stand, it seems like more of a technical/settings problem than a defective instrument. before sending the lens in, i would first try to eliminate the possibility of user error.
     
  17. The sharpness is crisp and beautiful. Don't see anything wrong with the lens.
    As we in systems loved and hated to say, this is "user error". Don't worry, it is a common disorder in these days of high-tech cameras and gadgets with deficient 1000-page instruction manuals that no one reads. Fortunately it is curable - one will see more "sharpness" and contrast when the blown-out highlights are recovered. User Erroritis is common. I suffer from it too - more than I care to admit. ;-)
     
  18. ShunCheung

    ShunCheung Administrator

    Related to the over-exposure, while having the flash on the hot shoe is not ideal, it has the advantage of simplicity. For day-time fill flash, I typically set the flash to -0.7 or -1.0 stop, give or take. That should help prevent the overexposure issue.
     
  19. All great suggestions. I'll try some of these. Appreciate it!
     
  20. Suggest trying a sample shot with the 17-55 at 50mm and also with a 50mm prime.
    If the zoom result is close to the prime, then you know the lens is OK.
     
  21. Wade, before you send this glass to Nikon for evaluation, you can take your time and test the lens yourself (at various mm and F-stops)...whether in AF or MF....and make a final decision based on what you're getting. Also, this may be helpful as to which parts of that lens you may wish to avoid.
    Les
     
  22. Try "slrgear.com" for their lens test reviews, thats if they have a review for your lens. They do comprehensive testing of lens with an very informative chart of the lens blur factor that can be set for both any aperture and focal length. I use the blur chart to help determine the best aperture for my lens to optimize my image capture to obtain the highest sharpness from the lens that I've been using.
    Keep in mind that most lens produce their best sharpness with the aperture set in its middle range.
    Example; If the lens has a maximum aperture of say f/2.8, stop the lens down to f/5.6 to f/8. You my find also that your lens being a zoom will have different optimal aperture/sharpness for the different focal lengths.
    Also, always use the highest shutter speed possible if your going to hand hold your camera, even with VR, which you don't have with that lens. And keep in mind DOF (depth of field) which is controlled by the aperture.
    There are hundreds of online tutorials that can help teach you more about the technical aspects of lens physics.
    Pete Resetz
    00dfF7-560020184.jpg
     

Share This Page