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Thread: How to Handle Overexposure

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    How to Handle Overexposure

    Iím fairly new to digital. I recently purchased a 645D and have discovered that a sensorís response to over exposure is quite different from that for film. IĎve attached an image taken with the 645D. Film would have likely yielded an acceptable image of the overexposed sun, but the digital image is very unappealing with an irregular pattern of pure white. I tried opening the file in ACR twice and pasting different exposure settings - somewhat helpful, but thereís nothing to be recovered in some areas. How should I handle a situation like this in the future? This was handheld and a tripod would not have been very practical, so multiple exposures would have been difficult. Thanks for any advice.

    Tom

    N.B.: I did post this at Luminous Landscape as well, so I apologize for the repitition.

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    Re: How to Handle Overexposure

    If you are working from a tripod it's a fairly easy thing to make multiple exposures and blend them together. So at a minimum, one exposure for the sun/sky and another for the foreground. Then either mask them into one image in photoshop or use the blend command. Or you might consider HDR to combine multiple exposures of scenes where the DR is beyond your sensor's ability to capture it in one exposure.

    Tim

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    Re: How to Handle Overexposure

    Digital capture, even with the best of the recent sensors, has a limited dynamic range compared to negative film. So if you can make only one exposure, you're more or less stuck in a situation like this - you need to decide what combination of highlight and shadow information you're willing to sacrifice for best overall effect. With experience, you'll be better able to judge how to peg the exposure to achieve a result you find most pleasing. In the meantime, it might be worth your while to bracket each scene. Even if your hand-held exposures can't be cleanly superimposed for HDR processing, processing the different exposures will help you learn how your camera behaves and calibrate your judgment of different scenes.

    EDIT: A second thought: you might also try using graduated ND filters. Not every subject with a long SBR lends itself to one, but when it "fits", it can make the difference in achieving a usable picture.

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    Re: How to Handle Overexposure

    Maybe GND filters can help here
    Tareq

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    Senior Member edwardkaraa's Avatar
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    Re: How to Handle Overexposure

    I think it would be best to expose for the highlights and open up the shadows later on in PP.
    M262 ZM 25/2.8 35/1.4 50/2 85/2

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    Re: How to Handle Overexposure

    Even handheld you can do exposure bracketing. You do have to make sure you capture wider than what you want to end up with eventually. Aligning the different images in PS will cause you to loose on all sites. Naturally you need try to capture the same frames as much as possible but it doesn't matter if it is somewhat off. The more it is off the more you loose with aligning the various frames of course.

    I would do this before opening up the shadows (while exposing for the highlights). Opening up the shadows in an image like this will be opening up a can of worms. Bad things reside in these shadows. Even with MF I find there is a steep penalty for opening up shadows.

    It goes without saying using a tripod would always yield the best results (potentially).

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    Re: How to Handle Overexposure

    In your case, with the sun more or less on the horizon, the best option is either a Singh-Ray reverse-gradient, or a stack of Lee/Singh-Ray graduated neutral density filters. You can fairly easily control the amount of exposure reduction applied. This is my preferred method of exposure control, as I feel as if it ends up looking the most "natural."

    There's also the method of bracketing your shots and blending multiple exposures to maximize dynamic range. Not a bad method; I've used it before. As long as you're only blending exposures, it will look fairly natural. I do not care for the "HDR" look made popular by the program Photomatix. I find that it destroys contrast and imparts a "Disney-esque" surreal feeling that is not always appreciated (or sought). Skip it if you want to maintain natural looking images.

    Last method is pretty ingenious, but it's only applicable to fairly lengthy exposures. Using a cloth, cover the top-half of the lens as to block out the light. Start the exposure, then slowly move the cloth upward, opening up the rest of the scene. It works fairly well, but again, only for longer (30+ seconds) exposures.

    Like I said, grads are my preferred method. The Singh-Ray reverse-gradient filter is a pure genius.

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    Re: How to Handle Overexposure

    Quote Originally Posted by Oren Grad View Post
    Digital capture, even with the best of the recent sensors, has a limited dynamic range compared to negative film.
    Oren, which digital backs and film have you shot that you are using for your comparative statement? Or are you judging based on numbers floating around (e.g. dX0 assigns X number of stops to camera Y)?

    Also, this is not just an issue of absolute dynamic range. A system with better dynamic range would allow you to recover better detail out of the area around the sun. However the sun itself (the very center sphere) will not fit in the dynamic range of ANY (non-scientific) capture device, film or digital, when exposing for the rest of the image. Nor, do I think most images would benefit from getting detail in the sun itself. So it matters how the sensor, a/d convertor, firmware, and software will handle the harsh transition from 'completely blown out' to 'bright highlight' and just as importantly how good the color fidelity and smoothness in those highlights.

    If you're curious how other medium format systems handle this kind of difficult image-quality-challange here is a sample IQ180 raw file shot by forum member Siebel:
    Phase One IQ180 Raw File

    Download the raw (please do not judge based on the compressed web-size JPG) and open it in Capture One 6. Look at the transition from blown out sun to the rest of the sky and play with the sliders to see how the file handles being pushed around.

    Since you already have the 645D my suggestion would be try the same file in a variety of raw convertors, each of which have their strengths and weaknesses. A different raw convertor might help you pinch a bit more out of your existing system.

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    Re: How to Handle Overexposure

    Quote Originally Posted by Dustbak View Post
    Even handheld you can do exposure bracketing. You do have to make sure you capture wider than what you want to end up with eventually. Aligning the different images in PS will cause you to loose on all sites. Naturally you need try to capture the same frames as much as possible but it doesn't matter if it is somewhat off. The more it is off the more you loose with aligning the various frames of course.

    I would do this before opening up the shadows (while exposing for the highlights). Opening up the shadows in an image like this will be opening up a can of worms. Bad things reside in these shadows. Even with MF I find there is a steep penalty for opening up shadows.

    It goes without saying using a tripod would always yield the best results (potentially).
    This ^^^
    -bob

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    Re: How to Handle Overexposure

    Quote Originally Posted by dougpetersonci View Post
    Oren, which digital backs and film have you shot that you are using for your comparative statement? Or are you judging based on numbers floating around (e.g. dX0 assigns X number of stops to camera Y)?
    Judging based on making pictures and wrestling with the files, using a range of raw converters. I've tried two medium format devices myself - ZD and Aptus 75 - as well as many different DSLRs both APS-C and full-frame, of which the most robust DR-wise have been the Fuji S5 and the Nikon D7000 at low ISO. I've also played with sample files that others have made with many other medium format and pseudo-35 digital cameras. As for films, many different B&W emulsions, and in color primarily Portra 160NC and 400NC, as well as the Kodak Gold/Ultramax consumer roll films.

    I agree that some camera/converter combinations handle the roll-off to clipping more gracefully than others. But in the end, digital capture still saturates sooner than negative film - necessarily so, given current technology. The shoulders of the negative films I use go on, for all practical purposes, forever. Some degree of tonal differentiation holds out well past the point where digital capture hits the wall, and when tonal differentiation is finally lost, highlights dissolve gracefully into the texture of the grain.

    Digital capture has many advantages, but the ability to pleasingly render the extreme brightness range represented by the OP's example through a single capture just doesn't happen to be among them.

  11. #11
    richard.L
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    Re: How to Handle Overexposure

    for a somewhat technical discussion try McCann's lectures at Google... here is a link to one

    http://www.youtube.com/user/GoogleTe.../3/ALfiTDYLtAQ

    don't be afraid of the HDR title... this doesn't mean he is going to tell you how to do exposure stacking in a generic or dedicated DET.

    richard. Laughlin... atop the Tejas Triangle.

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