Over / Under Exposure

Discussion in 'Photography Beginners' Forum' started by ccaballero, Dec 11, 2018.

  1. ccaballero

    ccaballero TPF Noob!

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    Hello TPF friends, I have a question that could not find a specific or more direct thread for it.
    I have a Nikon D3100 with a Nikon 18-200 VR (just as an FYI) and Im confused when it comes to Over / Under exposure, at witch end is the picture unrecoverable? Is it better to Under exposed if unsure or is it better to Over expose and fix in PP?
    Im aware this is only pertaining RAW / NEF files.

    Thanks in advance


     
  2. greybeard

    greybeard Been spending a lot of time on here!

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    As a general rule it it better to underexpose than to overexpose. Underexposed shots can be recovered (to a point) in post processing but overexposed shots can not. I look at digital much like I did when shooting color slide film. With this I had to expose for the highlights and let the projector take care of the shadows. With digital I expose for the highlights and bring up the shadows in post processing. There are exceptions to these general rules but as a beginner just starting out, expose or the highlights and process for the shadows is a good starting point.
     
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  3. ccaballero

    ccaballero TPF Noob!

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    Thanks, I notice I have been overexposing the majority of my photos and not using my exposure compensation enough
     
  4. ac12

    ac12 Been spending a lot of time on here!

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    Set your back screen to show highlights. Any place that blinks, is unrecoverable highlights.
    The tricky part is, unless you zoom in, you won't see the smaller highlights. In something like a large group photo, that blown highlight could be a face.
     
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  5. Ysarex

    Ysarex Been spending a lot of time on here!

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    Your original question begs further questions. You referenced NEF files in your original question: How do you know if they are over, under, or properly exposed?

    Joe
     
  6. ccaballero

    ccaballero TPF Noob!

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    Ysarex thats were I take the noob out for a walk LOL. I have my D3100 set to take both JPEG and RAW (I wrote NEF because that is how it shows in Capture NX-d) I might have this one very wrong. When I say overexposed is because I took a lot of pictures on Saturday on the bay, under a sunny sky at 3pm and the pictures were extremely bright, not all of them I did fiddle some more to get to a place were in my beginner sense were ok. But for some reason my starting point was always bright.
    I apologize if Im describing this wrong, or have the wrong idea in regards to exposure.
     
  7. Braineack

    Braineack Been spending a lot of time on here!

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    The D3100 has a hard time recovering in any direction -- but still, I'd rather underexpose than over.
     
  8. Ysarex

    Ysarex Been spending a lot of time on here!

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    Might not be a bad idea to show us a few of the photos that were extremely bright -- possible problem?

    An NEF file is a Nikon raw file. You have your camera set to save both -- good. The whole topic of exposure can be a bit of rabbit hole. Thinking about the NEF files which contain the sensor readout converted to digital values and not concerning ourselves at all yet with any image that you can see, data recorded is exposed within the sensor's threshold limits. Any data that we fail to record beyond the sensor's high end threshold is overexposed -- failure to record. Any data unreadable/indistinguishable from noise is underexposed -- failure to record. The data then that is recorded during an exposure ranges in "quality" (noise, detail, color fidelity, etc.) in direct proportion to exposure such that the data exposed the most is best and the data exposed the least is worst.

    Failure to record is unredeemable -- my niece would say duuuuh. The two limits (high end/low end) are somewhat different. The high end limit is very hard, crisp and sharp; think edge of a cliff. The low end limit is kind of mushy; maybe like a quicksand bog. I think we can call the low end a noise bog. Typically our camera's sensors record more data than we need to make a good photo. That means there's some breathing room; latitude for error or sloppiness or if you prefer room to hedge a bet.

    So if you're not confident about exposing a digital sensor and you decide you want to hedge the bet which way do you lean? You want to risk going over the cliff or find yourself knee deep in the bog? Most folks as was suggested above hedge that bet preferring the bog over the cliff. It's fairly reasoned that if you're knee deep in the bog at least you're not dead yet which we can't say for cliff jumpers. :)

    Joe
     
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  9. ccaballero

    ccaballero TPF Noob!

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    Last edited: Dec 11, 2018
  10. Braineack

    Braineack Been spending a lot of time on here!

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    get out of shutter speed mode if youre not going to set the shutter speed appropriately.
     
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  11. Ysarex

    Ysarex Been spending a lot of time on here!

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    The first photo is certainly badly overexposed. The second photo of the same scene is much better. There's slightly more than a stop difference between the two exposures but more than that in the two images and so we need to look for causes and possible trouble.

    The files indicate that you had the camera in an auto exposure mode. What was that mode on the camera?

    Right up front I see potential trouble: f/25. Did you set the lens to f/25 deliberately and if not back to the question above -- what exposure mode did you use on the camera?

    F/25 may well be the smallest possible aperture that lens is capable of. Trying to set a hardware max limit value could be an issue.

    The difference between the two photos is 8 seconds. I don't believe you made any change to the camera settings between the two shots so the exposure difference needs an explanation.

    My gut reaction would be to look to the lens aperture. All of our cameras operate using a methodology we call open aperture metering. The aperture stays wide open so you can see the image through the lens and metering is computed for the f/stop that will be set when you take the photo. You trip the shutter and the mirror lifts up out of the way. While the mirror is being lifted the lens aperture closes down to the set f/stop. F/25 would be the farthest mechanically that the aperture would need to close and if it's sticking even a slight bit then it could fail to reach the set f/stop before the shutter opens -- overexposure is the result.

    Joe
     
  12. Ysarex

    Ysarex Been spending a lot of time on here!

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    That would explain it. Shutter priority and the lens can't stop down any further than f/25. I was overthinking it.

    Joe
     

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