Exposure Help Needed

Discussion in 'Beginner Questions' started by arlingtonbeech, May 20, 2022.

  1. I have noticed recently that in post, my images of delegates on stage during conferences lack overall definition and are grainy despite being in focus. The images are backlit from the large conference screen.

    I shoot with a full-frame Canon with a 70-200mm lens @ 142mm. My settings were iso 800/f2.8/1/200th sec with a balanced histogram showing good overall exposure

    My other images, candids etc away from the stage were perfect

    Could it be that there is too much light coming into the sensor from the stage lighting that has contributed to the degradation of the image. Any advice appreciated.

  2. Maybe open the aperture up another stop or stop and a half, in relation to the shutter speed.
    arlingtonbeech likes this.
  3. Thanks very much Kmac, so you are thinking I am getting too much light on the sensor?
  4. It may be that the delegates, who probably occupy a relatively small percentage of the frame area, are underexposed because the backlighting is dominating the scene. I would spot meter on the actual delegates, or depending on the exposure mode, dial in plus 1.5 or 2 exposure compensation. I would also consider using a higher ISO than 800 in an indoor situation with poor lighting. Posting example pictures would help.
    kmac and rodeo_joe|1 like this.
  5. Thanks John appreciate your input. In actual fact the stage lighting wasn't bad for an indoor event. I shoot manual and in this image I made an adjustment - iso - 1000/2.8@200mm with my 70-200mm _P227235.jpg
  6. After seeing the sample shot, I'll echo John's suggestion that the bright screen is fooling the meter into underexposing the back lit subjects. Either spot meter from the people's faces, or use exposure compensation to add maybe 0.7 EV to the exposure.

    (A slight pop of flash would help too if it's permitted)

    Also make sure the lens is spotlessly clean. Back lighting can cause flare and degrade contrast with a misty or dirty lens/filter.
    Last edited: May 20, 2022
    arlingtonbeech and kmac like this.
  7. Thanks rodeo_joe1, I appreciate your input
  8. No, not enough light

    Your pic looks ok, but the lady is still a little under-exposed by about 3/4 to 1 stop. Back lit subjects need more exposure.
    arlingtonbeech likes this.
  9. Thanks Kmac - I initially thought it was a lens problem, but your contributions with others confirmed it is an exposure problem, Thanks again
  10. It would be helpful if you showed us the histogram.

    The suggestions to spot meter off the face to better expose the face make sense, except: (1) if the histogram spans the entire range, increasing exposure in that matter will cause some areas to blow out, and (2) regardless of #1, the imbalance--much brigher lighting behind the face than on it--will be unchanged. that is, the entire shot will be brighter.

    So, what I would do is one of these:
    (1) if there is room on the histogram, increase exposure (spot metering on the face would just be one way to do that), and then burn the background in post to darken it.
    (2) if there isn't room on the histogram to increase exposure, use the exposure you have, brighten the face by dodging, and darken the background.

    Unless you are blowing out the highlights, no. The problem comes from underexpositing the face.
    arlingtonbeech likes this.
  11. For backlighting normally you would have to blow out the highlight otherwise you underexpose the shadow.
    arlingtonbeech likes this.
  12. Seeing the brighter background and light colored clothing worn by the subject (in the OP's image), I would have added some exposure to help maintain detail in the subject's face knowing that I would inevitably need to lift the shadows in post processing. With mirrorless I would have added exposure until I saw the highlight clipping indications in my EVF and then backed off the EV comp dial. Same could be done with a DSLR with a test image. In this case, I would expect that any modern FF sensor would have enough DR to manage that image without blowing out the highlights. It would been fine even using my M43 camera with its much smaller Sony sensor.
    arlingtonbeech likes this.
  13. If it has to be done in post, the dodge and burn tools aren't the best option. They're unsubtle at best, and downright crude at worst.

    A better option would be to shoot RAW and use the 'preserve shadows' and 'preserve highlights' sliders in the raw developer if available.

    Failing that, create a brighter shadow layer using the curves tool, or exposure slider in RAW. Lower that layer and rub through the top (normally exposed) layer using a low opacity eraser brush to reveal the brightened shadow areas where necessary. Slightly more work, but much more subtle than dodge and burn - which can just look as if white or grey paint has been sprayed on the affected areas.

    Here's that exact technique used to brighten a grossly underexposed foreground while keeping a brighter sky well-exposed.
    Original SOOC.

    2nd brighter layer created from RAW file and foreground rubbed through using eraser tool:
    Last edited: May 20, 2022
  14. Really. Who knew?

    I actually didn't suggest using the dodge and burn tools. I suggested dodging and burning. Since you assert that this is "downright crude", I'll give you the method I usually use, which was given to me by an expert photo retoucher. I'll use dodging for an example, as it would be more important in the OP's image.

    1. add a curves adjustment layer, bring up the midtones (or other parts of the curve if you want to be fancy) until the area that you want to dodge the most is at least as light as you want. No harm in going a bit farther, as you'll see.
    2. Invert the mask.
    3. Select fairly soft white brush (hardness depends on the image), with 100% opacity and a very flow flow. I typically use between 9% and 12%. This is important, as opacity and flow work very differently when you are attempting to build up an effect.
    4. Slowly paint on the burning where you want it, building it up more where you want a stronger effect.

    The advantage of this approach is it completely separates relative amounts of burning, which you control with the brush, and the absolute level of burning, which you can control by changing the curve itself. And, of course, you can lower opacity.

    Somewhat similar to your second method, except that it dispenses with the superflous steps and pixel layer.
  15. Ahhh, Paddler, this is the internet, where your every word will undoubtedly be pounced on by the Internet Corrector Brigade. So, when you say dodge, in order to correct you and appear just a bit mightier than you, it’s assumed you mean the specific tool rather than the concept behind it. The thing is, no matter how hard you try, you won’t be able to avoid this, because language, like humans, is never perfect, so you won’t ever pick just the right terminology or phrasing and someone will always be lurking in order to one-up you. The best you can do is the best you can do, allowing the sore thumbs to do what they do best. The other readers will decide the relative worth of each post and will decide for themselves how important is a strict adherence to absolute definitional precision and poster self satisfaction.
    Last edited: May 21, 2022
  16. Ah, samstevens, in general, I agree, but I don't think that was the problem here...

    I was actually being precise. "Burn" doesn't mean "use the burn tool". It means the process. When I started out, it usually meant waving a piece of cardboard with a hole cut out of it underneath the enlarger. Even people inexperienced with photo editing can find 3 or 4 (or more) ways of dodging and burning with a quick web search, most of which don't use the dodge and burn tools. For example, this page has 4 methods, only one of which uses those tools, and it's not a complete list. It omits at least one common one (which I never use), which is using a neutral gray layer, e.g., Photoshop Dodge and Burn with 50% Grey Layer – SLR Photography Guide.

    I've had some back and forth with one very experienced retoucher about this. He often uses selections, but I find it hard to get smooth transitions that way, so I use the method I posted, which he also taught me. One additional advantage of this approach over some others is that it makes it trivially easy to reduce the dodging and burning. Just switch the brush to black. As long as the flow rate is very low, you can make fine adjustments that aren't at all apparent in the final result--that is, you can't tell where the boundaries are.
  17. As I said, I’m not going to make an issue of precision of terminology.

    I use similar methods to yours. You’ve described them well and that should be helpful to the OP.
  18. Exactly!
    Much more helpful than 'dodge' and 'burn'.
  19. You just can’t help yourself. :(
  20. Paddle
    Paddle4 thanks very much for this. From the comments made I am now clearer as to where the problem lies. I tried to be too clever by half to get a clean sponsor's logo on the projector screen when shooting wide shots by exposing for the highlights on the screen. I maintained this exposure profile when I came in for close-ups hence the under-exposed subject. I checked the histogram at the time which was fairly balanced. After your comments I can see that there was scope to push the histogram further to the right to better expose for the subject and to react to any highlights from the screen in post. I have learned a couple of valuable lessons through this post. Thanks very much.

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