Inconsistent exposures with D90

Discussion in 'Nikon' started by owen_farmer, Sep 11, 2010.

  1. I just returned from a trip out West with my newly acquired D90 with a Nikon 16-85mm VR lens. In general I found that the camera overexposes 1/3 or 2/3 stops. That is easy to correct, but inconsistent exposures are troubling. Here are a few examples from shots around Crater Lake in Oregon. In all cases matrix metering was used with 0 exposure compensation. Also, there was a polarizing filter attached, but I don't know how the filter was turned (in some pix it is obvious). When there is a high polarizing effect the exposures are good, but otherwise overexposed.
    00XGSq-279511584.jpg
     
  2. Can I attach multiple images to a single post? Anyhow, here is another image of Crater Lake.
    00XGTO-279519584.jpg
     
  3. I don't know how "bad" the second one is, doesn't look like many blown highlights to me. Just a flatter image. Yes I like the first exposure better, but the second one just probably needs a polarizer...
    However...
    I would shoot these aperture priority not shutter. That's what I noticed looking at the EXIF data. Shutter Priority is great for sports, but for landscapes, aperture is more useful.
     
  4. Why don't you do a test without the filter? It'll take only a few minutes to decide if the filter is the reason.
    Most people here would do that if they have your camera in their hands
     
  5. To my eyes, the first photo appears underexposed. Go figure.
     
  6. What brand polarizer are you using ?
    One shot is F8 and 1/250 , the other is F11 and 1/125. If my math is correct, that is the same exposure. So the camera read both of those as the same EV value.
     
  7. OK if you are only shooting *.jpg from the camera ignore my post, continue if you shoot RAW.
    Please keep exposure and processing apart.
    To be certain if highlights are blown (overexposure) you have to look at the raw data using a dedicated software that can evaluate the raw data or a RAW converter that will do so reliably.
    Otherwise the way your exposure looks depends on the RAW converter and especially its settings.
    I use Adobe Camera RAW 6.2 for conversion. It will show clipping of individual channels and this is fairly reliable. If there is no clipping but the image looks too bright exposure will be at best (exposure to the right). If this is the case you did not loose any information in the highlights and get the least amount of noise in the dark parts of the image.
    If this image without clipped highlights looks too bright and overexposed (which is not the case in the raw data) simply turn down brightness and or play with exposure, contrast, saturation, black point, camera profile etc until you get the look you like best.
     
  8. Walter,
    I believe the OP was trying to determine if his camera was doing something it shouldn't, not trying to figure out how to fix it, in post production.
    At least that's how I read his post.
     
  9. I think primarily what you're seeing is your camera's metering system exposing for different things. In the second shot you've got a lot more dirt/rock than you do in the first.
     
  10. The only way to truly determine if your camera is underexposing is to compare the meter in your camera to an external meter you know is accurate. While our eyes will detect obvious metering errors, more subtle meter reading variations can only truly be determined if you approach it from a more scientific method. I'd do a bit more investigating to determine the true cause of your "apparent" underexposure before compensating.
     
  11. more scientific method​
    agree
    more investigating to determine the true cause​
    exactly. I would do more experiments and get more data before guessing anything
     
  12. I have been shooting JPEG and not raw.
    I have a Sekonic L-308S digital meter, but I don't see the point of checking the accuracy of the D90 vs. the Sekonic. The issue is apparent inconsistency. It seems to me that the camera's metering system is likely doing what it was designed to do, i.e., "exposing for different things", but that is a problem if I am relying on the smarts of matrix metering and it is not giving me what I want. For 30+ years I have been using Olympus OM 1/2 (with manual exposure). My practice had been to scan a scene, noting the exposure reading and decide whether to slightly over or underexpose. My results with slide film were good overall. I am wondering if for scenes with a large range of light intensities I would be better replicating that procedure by putting the D90 in manual exposure (and get an analog exposure display) and choose center weighted metering.
    I used a Tiffen circular polarizing filter. The next time I am shooting something similar I will experiment with the polarizer on and off, but whatever the answer I am not sure what I would do with the answer, particularly if I don't have the problem with manual metering. As suggested, some experimentation is in order.
    BTW, Active D-Lighting was on Auto.
    Thanks for the help.
    Owen
     
  13. "a problem if I am relying on the smarts of matrix metering"
    Don't forget that you are driving your camera. No matter how "smart" it is, check the output and adjust the camera (EV, Shutter, Aperture, etc) .
     
  14. if I am relying on the smarts of matrix metering and it is not giving me what I want.​
    Usually when some thing tries to be smart, it may become a smart-xxx. The manufacturers put a lot of things in their cameras because they cannot know what works for you, what you like and what you don't. You make your choice
    My practice had been ...​
    You don't have to change the method that you had been used, just notice that the digital sensor may behave a little different from your film. But the easy part is that you have only one sensor
    I am wondering if ... I would be better ...​
    Do what you want to do, what is more convenient, more efficient, more successful to you
    putting the D90 in manual exposure ....​
    Manual exposure is good. Try to use it as much as you can. I do that all the time
     
  15. The "sunny 16" rule never fails me, the most up-to-date DSLR's in the world aren't always going to be right. This is where manual exposure and RAW comes in just ideally.
     
  16. Different camera bodies will meter an identical scene differently. Different people will prefer one exposure over another for a particular scene and there is really no one absolute correct exposure for any photo. Shots that have both light and dark areas in them are the most difficult for a camera to meter correctly because only the photographer really knows what 'look' is desired.
     
  17. Owen if you do landscapes and manual metering worked for you for a long time then go ahead and continue with the way that worked, especially if you want to do jpg from the camera.
    Just set everything to manual in your camera and that excludes auto anything (like auto D-lighting) since anything auto is out of your control. Measure light with your light meter and set A and S to your estimate from your "Bio-Computer". A trained photographer will do better any day than matrix metering unless you shoot action.
    You can get a lot of help from a modern camera by shooting bracket series. I often shoot 3 images with +- 0.3 whenever dynamic range is small up to 5 or even 7 shots at +- 0.7 if the dynamic range is large. Storage space is cheap and this way you will always get a perfect exposure.
    Your only switch from slide film will be a little bit of fine tuning to get to jpg shooting.
    There is no reason to use all the high-tech gimmicks if your system worked well for decades :)
    You would still have to do some in camera settings for say contrast, sharpening color saturation etc that will modify the in camera processing. That will take some time to optimize.
    Happy shooting.
     
  18. I had the same problem with my D90, with a 16-85 and 70-300. One day on a trip to the mountains the exposure was suddenly unpredictable. I sent the body to Nikon -- they made corrections and it's ok now.
     
  19. Start with using integral metering. Matrix metering is totally unpredictable. If you take several pictures of the same subject and while moving around a bright or dark object moves to another segment in the matrix metering, the overall measurement will be different. This is less of an issue with integral metering. When you really want to do it properly, use spot metering and manual settings.
     
  20. The more I think about it, the more I'd like to hear what Nikon repair might say. By all rights, the meter should have seen the second shot as brighter and wanted to make the large amount of dirt more 18% gray, which would have darkened the shot. Yet, by the EXIT data, it determined that each was an identical over all brightness. Since the OP is using a name brand circular polarizer, I don't expect that to throw the meter off.
     
  21. Hi Owen,
    I think the key to your "problem" may be:
    In all cases matrix metering was used​
    If I remember the discription of matrix metering correctly, the camera meters the entire scene, compares it to a database of scenes, and make the appropriate correction. All it takes ia a slight change in lighting for the camera to select another database entry and change its correction.
    It would be instructive to set the meter to centerweight or spot, meter off the same area, and see if the problem persists. If it does, you have a problem with the meter. If it does not, you have met one of the problems/features of matrix metering.
     
  22. Owen, I personally do not think one should expect perfect exposure in every shot, especially where there are portions of the scene that are much brighter or darker than the rest of the scene, or just very bright or very dark. The automation is handy, and often very good.
    First, as to the circular polarizing filter. Nikon itself, in the instructions for its own CP filter, recommends using center weighted metering with digital camera bodies instead of matrix metering. The polarized light is apparently not always going to give the best results with the matrix meter system.
    Second on using the CP filter. One should be able to rotate the filter while viewing the scene to see what the orientation is doing to the scene. The easiest places to look are the sky, clouds, and reflections off foliage, like tree leaves or the grass in front of you. Just turn it and see what you get. When it is not needed, it will reduce the light coming in and possibly degrade the image, say with reflections, etc.
    Chimping is good. I.e., check out the display. I do not have the D90, but it should have a histogram to view after the shot is taken, and one can set the display to show blinkies in highlight warning mode, which are likely, but not certain, blown out portions of the image. BTW, are you shooting raw or jpeg? The raw mode has more latitude to accommodate a wider dynamic range of exposure. The blinkies in the highlight warning mode are from the jpeg image that is contained in every Nikon raw file, which is narrower dynamic range than a raw file. So, there is the hope that what is looking blown out in a jpeg file might just be OK in raw, or retrievable in raw. However, to shoot it right, the goal for all of us I guess, is to check the display after each shots. For landscape, it is always best to check that histogram and/or take several exposures with over and under exposure.
    If the scene has difficult light, such as sky and darker foreground, why not do some bracketing using the continuous shooting mode? The camera has that feature, and you can simply pick the best exposure later on.
    Choosing a exposure measuring mode. Matrix is an educated guess by the camera's computer. However, nature, and the photographer behind the camera, will always find scenes that will not be accommodated by the matrix meter 's algorithm. If there is one portion of the scene that is most important to you, try using spot metering mode. Many years ago, when I had an SLR for film that only averaged the entire viewfinder, I used to pine away to have a spotmeter. One degree hand held spotmeters were on the market, but they were too dear for me at the time. We now have that wonderful tool right in the camera body now. My old accommodation trick back when shooting outdoors used to be to take an average meter reading off my hand held in sunlight, and then put that same setting into the camera in manual mode. No reason why that cannot work now. Sort of the poor man's Sekonic.
     
  23. Unless you are in shadow and the scene is not.
     
  24. Well, I thought it was obvious, that the light must be the same. I suppose I should have said it more completely. Though, one of the averaging cameras I used to use was an Olympus OM-2n, similar to the OP's experience. He may have resorted to the same trick. It is harsh sunlight which afflicted both of the OP's photos.
    Of course, if everything were in shadow, an averaging, or matrix, or virtually any kind of metering would have a good chance of coming out OK.
     
  25. I am using the D90 in RAW (matrix metering most of the time) together with Photoshop in post processing. I have also observed the inconsistence of the results, when first viewed in ACR. Currently, I just fix the exposure in ACR and that's it. Only with very much contrast I find blown highlights. But it would not occur to me to blame the camera for this.
    I also tend to fix the brightness in Photoshop towards the lower side, because colors look better then. I do this by adjusting the middle slider in the tone curve dialog. Turning down the brightness in ACR gives not so good results, strangely.
     
  26. Thanks for the the responses. David Ralph's info that matrix metering should not be used with polarizing filters is appreciated. I made some measurements comparing the D90 exposures with readings from my Sekonic L-308S as follows. I laid a gray card on the grass in bright shade on a sunny day. At 1/30 sec the Sekonic read f8.0,6 (about 1/2 an f-stop between f8 and f11 for both reflected and incident readings. I set the camera to shutter-preferred at 1/30 sec and the 16-85 lens to 50mm and the ASA at 200, non-auto. I moved close enough to fill the viewfinder with the gray card image, focussed and shot. With matrix metering the pix info showed f7.1. With centerweight the pix info was f9. This says to me that matrix metering should not be used for atypical scenes. The centerweight reading was about +1/3 f-stop compared to the Sekonic. That agrees with my observations of actual photo exposures, ie., that I should usually set the camera to -1/3 exposure compensation.
    Owen
     

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