d7000 focus with nikkor 35mm

Discussion in 'Nikon' started by photomarche, Nov 26, 2011.

  1. Hi,
    I just bought a nikkor 35mm f1.8 to use with the d7000.
    I did some focusing test tonight, taking pictures of a mobile phone keyboard under artificial light.
    • ISO 100
    • RAW
    • Aperture priority
    • White balance auto
    • tripod
    • shutter cable
    • Mup
    I focused on the keypad, on the button "ABC", only ones than i turn the focus to manual and change only the aperture from f1.8 throughout all steps to f22. The keypad is approximatly 50cm away.
    On ViewNx2 I magnified each picture to 2x, I got the best sharp result at f8-f11. The keys are all blurred from 1.8 to 5.6, improving with greater steps.
    According to dpreview, this lens achieve the best sharp result around f3.5, whilst in my test the keypad appeart be blurred at 2x, and perfectly sharp at f8. For smaller aperture (e.g.above f16) it is a blur, but this is probably expected due to diffraction.
    I do not understand why the images are not perfectly sharp at f3.5 or f4 for example....
    Now, could the test enviroment (e.g. light) affect the result? I am going tomorrow to take some day shot with the tripod and see...
    I am very reluctant to use the af fine tuning, it is a trial and error approch and could make things worst, nor I believe that the d7000 has focusing issues....
    What do you think?
     
  2. My first though is about a photographer`s focusing error.
    Are all the keypad simply blurred? Have you checked if there is a focus shift? Which was the shutter speed?
    From what I have read, this lens should perform very good even wide open on your D7000.
    Your comments about light quality make me wonder... I`d repeat the test under really good daylight or flash. Focus on a contrasty subject, something like a newspaper. Manual focus and AF.
    Could you post a 100% crop? What about the f4 pic?
     
  3. tests:
    1) 1/13s @ f/1.8
    2) 1/8s @ f/2.2
    3) 1/6s @ f8
    Yes, It could be the light or something else in the enviroment....
    What would be a moreprofessional way to test this, what are the pro-photographer using? maybe I need to buy some charts?
    00Zeur-419399584.jpg
     
  4. Some lenses can focus close if focused manually, but do not focus equally close when on auto focus.
    What is your lens minimum auto focus range on D7000 ? Manual focus is 30cm and is camera independent.
    Step back a bit and try again ?
     
  5. If you were closer than about 10 inches, then, you may have been too close for the lens.
     
  6. This shutter speeds seem to me a bit... "unfriendly". But with the mirror locked up, a sturdy tripod&head and a solid floor there should not be a problem, I think.
    Anyway, I`d use better light (much better!) to repeat the test.
    I like to use an USAF test chart (just a home printed copy) for testing. It has black over white bars, in numbered groups of different sizes, easy to differentiate and evaluate.
     
  7. I am enclosing the sample at f/8, it looks sharper to me. Same distance, settings and light condition.
    Tomorrow I will test again with daylight and different subjects...
    00Zev8-419403584.jpg
     
  8. Looking at your pic I`d not say it is a sharpness or focus issue... at a first sight it seems to me very sharp, or should I say extremely sharp for a wide open pic, even with camera shake???
    You have an issue with your tripod setup. Congrats for your purchase. Looks to be a great combo.

    The f8 pic looks to me just slightly better, as expected. No camera shake here.
     
  9. thank you Jose, I ll use one of those USAF test chart you suggested.
     
  10. The focus point appears to be slightly in front of the phone which would explain your results.
    I prefer to use a 3-D object when testing a lens in the manner you did, I would lie the phone down, focus on the middle set of buttons and and re-shoot. And as Jose recommends, use higher shutter speeds.
     
  11. To start with your dof isn't going to be much at this distance. The fact that things got sharper at smaller steps indicates you probably didn't focus as perfectly as you thought. I don't really see anything in this shot which is in sharp focus, but that could be because you didn't sharpen your raw image.
     
  12. Also, you might want to check how the diopter adjustment on your camera is set, assuming you focused manually.
     
  13. Is that a "real world test"? If not, do one that is more realistic. non-micro lenses are rarely at their sharpest up close. Could be that at more "typical distances", f3.5 really is the sweet spot for sharpness. Those tests you are comparing to are not done at 10 inches...
     
  14. You can't tell anything shooting a subject like that under that lighting, and it tells you less than nothing if you didn't use a tripod.
    Try doing something like this - Camera AF Microadjustment- for free: http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html
    I check to see if AF fine tuning helps with all of my prime lenses. The moire pattern test referenced above by far the fastest, because of the least ambiguous test results.
     
  15. agree with elliot the first shot looks like front focus at the bottom of the phone. at f/8 this is less of an issue than at 1.8 because the plane of focus is deeper. if your distance was 30cm, that's right about at the limit of the 35/1.8 --29.9 cm according to Nikon-- and close enough to be within the margin of error. step back a little bit and try again. also agree that the lighting isn't great and shooting a 3-d image, or one at a longer distance, tells you more about the lens' characteristics than the shot you chose. i would only AF fine tune as a last resort, after eliminating any possibility of user error.
     
  16. Have you checked that the f1.8 shot is with the camera tilted? The plane of focus is in the front of the bottom of the phone, at the back in the top of the phone. This plane could easily goes across the "ABC" button(or, at least, very close).
    The second issue I see, is that the shot could be under the effect of camera shake (don`t know if subject shake). Check the house icon in the phone, and above; there are clear double lines. They could be of course produced by a "bad bokeh", (I`m not sure, it seems to me too much close to the focus plane, but who knows... ). It makes me suspect about the rigidity of the setup.
    Third, at f1.8 and 1/13 sec. light conditions seem to me a little poor for hand (eye) focusing; don`t know about the diopter correction and visual accuracy of the user with a DX screen designed for an "AF mostly" camera. I personally would not be able to focus under that conditions. Add to this that the lens is brand new on the latest Nikon model... (we could give Nikon a bit of credibility on the quality of his products).
    If the car doesn`t run... check first the fuel tank level. We can always think that even the most reputable car manufacturer could have a failure on the latest connector that goes from the air conditioner system to the whatever but... after checking that there is fuel on the tank! :)
     

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