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"Sweet spot" (distance from subject-wise) for 75mm f1.8 lens??

Discussion in 'Native Lenses' started by MaryAnnMachi, Jul 13, 2015.

  1. MaryAnnMachi

    MaryAnnMachi Guest

    Greetings, I've noticed with my 12-40mm Pro lens that the best shots (most sharpness) come when I'm about 100 feet from the subject, shooting at or near 35mm. I can't yet find an optimum distance with my 75mm lens, if there is one. Usually shoot about 1/320 sec. and above and have tried near, medium and far distances. Just can't get a sharp image, even on tripod. Beginning to wonder if I have a bad copy of this lens. Or maybe it's just operator error! Any advice appreciated.
  2. kevinparis

    kevinparis Cantankerous Scotsman Subscribing Member

    Feb 12, 2010
    Gent, Belgium
    100 feet?... is that a typo? That seem awfully far away.

    The 75 is a sharp lens... across its range... suspect either user error or perhaps a bad copy of the lens. Can you post some examples, maybe we can narrow down the problem

    • Agree Agree x 2
  3. MaryAnnMachi

    MaryAnnMachi Guest

    100 feet is correct for the 12-40 lens. Get some very sharp pix at that distance.
    The 75 not so much. I do see the ISO is 640 on this image. I usually aim for lower.
    Hookton Road hay bales.JPG
    Subscribe to see EXIF info for this image (if available)
  4. hazwing

    hazwing Mu-43 Hall of Famer Subscribing Member

    Nov 25, 2012
    what aperture did you shoot this with? By not sharp, do you meant the foreground is out of focus?
  5. Drdave944

    Drdave944 Mu-43 All-Pro Subscribing Member

    Feb 2, 2012
    I get sharp images all the time at all distances using auto focus/center focus. For sunny day I use A mode, ISO 200,widest aperture you can get without overexposure, probably about f2.8. Use IS 1.Touch screen works well so point at subject and auto focus locks on and it also takes the picture. You get a sharp picture every time. Only time you have trouble is macros ,where you use manual mode and magnify picture before focus. If you are having trouble something is wrong. Try manual focus . What are your results here? What body are you using? They should all work.
  6. DeeJayK

    DeeJayK Mu-43 Hall of Famer

    Feb 8, 2011
    Pacific Northwest, USA
    I agree with @kevinparis@kevinparis that a 100 foot working distance with the 12-40 at 35mm seems pretty long. In fact, I'm not sure I've ever heard of your concept of a "sweet spot" working distance for a lens. I'll admit I'm not a pixel-peeper, but I've not noticed any distinct differences in sharpness based on working distance with any lens I've ever used (obviously beyond the minimum focusing distance of the lens). Perhaps I'm simply not as discriminating as you are.

    I also agree that the best way to solve this mystery would be if you were to provide sample images that show us what your concern is. It would help if these images were shot with the most favorable and consistent conditions in terms of ISO, lighting and camera stability. I'm not sure that the image above is enough to diagnose any issues with the lens or anything else, particularly absent information about the aperture, focus point, etc.
  7. MaryAnnMachi

    MaryAnnMachi Guest

    1/1600 of a second. I realize the foreground is out of focus. It's the general sharpness of the images I'm getting with this lens.
  8. MaryAnnMachi

    MaryAnnMachi Guest

    I'll take a bunch of shots with those settings and check the results. I have an Oly OM-D E-M5. I have been using the EVF so maybe that is part of the problem. Thank you.
  9. MaryAnnMachi

    MaryAnnMachi Guest

    My question is more related to the 75mm. Just saying I have had better success with a particular range/distance with the zoom & wondered if the same applied to the fixed. Sweet spot is an old concept. I'll be working on shooting a batch. Thank you.
  10. DeeJayK

    DeeJayK Mu-43 Hall of Famer

    Feb 8, 2011
    Pacific Northwest, USA
    I've heard the term "sweet spot" referring to the aperture that delivers the sharpest image for a given lens (which is generally a couple of stops from the lens' maximum aperature), but I've never heard this term used in reference to a particular distance from subject.

    1/1600 is a shutter speed, not an aperture. Aperture is measured by f-number (or f-stop) and is a ratio of the focal length to the size of the hole through which light is allowed into the lens.
    • Agree Agree x 1
  11. felipegeek

    felipegeek Mu-43 Enthusiast Subscribing Member

    Jan 8, 2014
    Miami, FL

    Just note that MFT cameras, due to their smaller sensor, start losing sharpness at and above f8 due to diffraction depending on the lens. At apertures above f11 its gets unsharp rather quickly. Another thing that might be affecting your shots is shutter shock where at certain shutter speeds (1/10th-1/200th) the vibration created by the shutter actuating causes the image to become blurred. However, looking at your image I'd think this was shot at a wide open aperture (maybe f1.8-2.8) due to the foreground hay bale being quite a bit more out of focus with the focal point at or near the the electrical pole. The far background is also quite out of focus comparatively.

    Try a set of controlled shots with the camera preferably mounted on a tripod, of a similar scene at different apertures f1.8 through f8 in 1-stop increments in aperture prior mode (A) while always focusing on the same target in the middle of the scene. The shutter speeds will vary since the camera will decide what to set that at in (A) mode. You should find that at f1.8 the target you focused on should be sharp but the foreground/background elements should be quite out of focus starting relatively close to the target. At f2.8 the target will sharpen more and the fore/back elements will get a little more definition to them. At f4 the definition of the fore/back elements will improve more still. By f5.6 most of the image should be reasonably sharp with the focus point very sharp. At f8 it should be sharp all around. Note the intensity of the out-of focus area will vary depending your distance from the target and the distance of the foreground and background objects from you and the target. You are looking for the relative difference between each test shot on the same scene to judge the behavior of the lens. Additionally, If you notice that some shots the entire image is a little blurred as if the camera was shaken slightly check the shutter speed that the shot was taken at that may be the shutter shock I mentioned earlier.

    If regardless of aperture the shots appear unsharp (soft) at the target then you may have a lens problem.

    I hope the information was useful.
    • Like Like x 1
  12. gr6825

    gr6825 Mu-43 Veteran

    Oct 10, 2012
    Bjorn Rorslett often comments on how a lens performs at various distances.

    The obvious example is a macro lens designed to perform well close up. The Nikkor 55mm f/3.5 is one example.

    "The 55 mm Micro was optimised for close-ups with peak performance at 1:10 magnification, and the image quality suffered when it was used for landscape shots." LINK

    Here are his comments on the 28mm f/2.8:

    "Images taken up close really are extremely sharp in the middle part of the picture and sharpness extends quite gracefully into the corners. Optimum near-focus sharpness is obtained at f/5.6 and f/8. For distant scenes, however, corner sharpness isn't that remarkable and ghosting under adverse conditions can be troublesome." LINK

    Of course, "sweet spot" can be a little subjective. But I think the OP is just wondering whether the 75mm is optimized to give the best performance at certain distances.
  13. MaryAnnMachi

    MaryAnnMachi Guest

    My apologies for asking a confusing question. If I may restate it: I'm having a lot of trouble getting a sharp image with my Oly 75mm f1.8. Is there an aperture(s) where I'm likely to get a better image? Are there any settings that contribute to a sharper image? (Disregard any of my initial comment re: the 12-40 lens.) Must one always use a tripod to get a sharp image. I thought using a fast shutter speed might work, at least in some circumstances. Thank you again.
  14. 50orsohours

    50orsohours Mu-43 Hall of Famer

    Oct 13, 2013
    Portland Oregon
    You do turn off the IS when the camera is on a tripod yes?
  15. MaryAnnMachi

    MaryAnnMachi Guest

    Definitely helpful. Thank you.
  16. MaryAnnMachi

    MaryAnnMachi Guest

    I will. Thank you.
  17. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    As far as I know focus distance usually does not influence the image sharpness. The main exception that I know is infinity focus where some lenses performs differently when at infinity.
    I've read of a couple of famous portraits lenses (Zeiss?) that have been redesigned to optimize a specific focus distance minimizing aberrations at that specific distance (a couple of meters). But my impression is that it was something extremely subtle like apochromaticity and similar concepts. I suppose the same goes for macro lenses.

    In other words I do not expect the focus distance to affect the image so much to be clearly visibile in a generic shot like the one you posted. That is actually not much sharp. I suppose it is the full image scaled down, correct? Or is a 100% crop?

    Even diffraction shouldn't affect the image that much. Shutter shock at 1/1600 is strange. Where did you set the focus point? What aperture? At 1.8 the DoF in front of the subject is quite small even focusing at 100 or 200 meters. The 75 is good at all apertures (except for a little diffraction).
  18. gr6825

    gr6825 Mu-43 Veteran

    Oct 10, 2012
    If you can find any examples, it would help with diagnosis. Judging by the online reputation of the 75mm, you should not be having trouble with sharpness unless: (A) something is wrong with the lens; or (B) something is wrong with your technique.
  19. MaryAnnMachi

    MaryAnnMachi Guest

    That probably explains why all my tripod shots were not sharp. I thought using a tripod & remote would solve the sharpness problem. Will try again with this change of settings.
  20. tkbslc

    tkbslc Super Moderator

    I think this moves into the realm of worrying way too much.
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