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Thread: Need Help with HDR

  1. #1

    Need Help with HDR

    Hello all I’m new to the HDR. So if you can help please do so. I have a SONY A350 it take 3 photos in RAW format. But it not much different 1st -0.3 2nd 0 and the 3rd is +0.3 or the other setting is -0.7, 0, +0.7. So my question is can I somehow go in Photoshop CS5 and change the EV or something els on the same photos and save as new photos then do the HDR

  2. #2

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    Re: Need Help with HDR

    Hi "dwalley",

    Welcome to CiC - it's great to have you with us. What's your first name?

    HDR is needed when the dynamic range (or "range of brightnesses") in a scene is too much for the sensor in a camera to handle in a single exposure - so we break the scene down into several shots, with each capturing a portion of the scenes dynamic range. In the vast majority of cases there is little point in capturing information less than 2 stops apart; steps of 0.3 or 0.7 are pretty close to "nothing" (as you've already discovered).

    Unfortunately, "changing the EV in Photoshop" isn't possible because it's all about the information that's been captured. Information that's too bright for the sensor to record isn't recorded, and no amount of adjustment in Photoshop is going to reveal something that wasn't recorded in the first place. Conversely, if the light levels are too low then the shadow detail gets buried amongst the sensor's background noise, and no amount of processing is going to seperate the two.

    What DOES confuse a LOT of people though is the fact that the average camera sensor does capture a LOT of information that we can't see without manipulating it into a range where it's visible; Case in point, your A350 is capable of recording a dynamic range covering 11.5 stops, and yet the average monitor is only capable of displaying around 6 stops, and the average print only capable of displaying around 4 stops ... so there's already a LOT of information hidden away that we can make good use of.

    In terms of what you're trying to capture, for starters, I'd suggest adjusting your exposure so that you just just just just capture the highlight detail that you need (ie push the histogram all the way to the right, but not over) (so no big spike at the end) and then use the FIll Light control in CS5 to reveal the darker areas ... 9 times out of 10 there's more than enough detail already contained in the capture, and HDR techniques aren't required.

    If you DO require more than 11.5 EV of dynamic range (which is possible, although unusual), then you'll need to get the camera taking multiple exposures that cover the necessary range, at around 2 stop intervals ... I'd suggest shooting in manual mode, and being very careful not to move the camera (on a tripod of course) whilst making the adjustments.

    We've had some good discussions about this in the past, so you might find these threads helpful ...

    So I had not really tried shooting a human yet - HDR philosophies

    Tone Mapping

    Also, you might get a better understanding of HDR in this thread ...
    Evolution of a Newbie - HDR software, technique, etc


    Hope this helps
    Last edited by Colin Southern; 15th October 2010 at 09:51 PM.

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    pono's Avatar
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    Re: Need Help with HDR

    I used the HDR function on CS3, and I think I had about 5 shots, shot on a tripod, but when the program merged all the photos, they weren't lined up correctly. For example, th subject was shown multiple times in different parts of the frame, with the different exposure rates.
    Any suggestions?

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    Re: Need Help with HDR

    Quote Originally Posted by pono View Post
    I used the HDR function on CS3, and I think I had about 5 shots, shot on a tripod, but when the program merged all the photos, they weren't lined up correctly. For example, th subject was shown multiple times in different parts of the frame, with the different exposure rates.
    Any suggestions?
    This can happen if the camera moves between shots - if you vary the exposure by varying the aperture - or if the camera refocuses between shots. To get around it ...

    - Use a sturdy tripod - remote release - and mirror lockup (or lifeview)

    - Focus the camera and then switch to manual focus

    - Vary the exposure by varying the shutterspeed, not the aperture

    - Tell Photoshop to automatically align the images (if you have that feature)

    - See if you REALLY need HDR at all; often by shooting RAW folks can recover plenty of shadow detail by simply using the fill light slider in ACR (just be sure to push the exposure to the max in the first place).

  5. #5
    Shadowman's Avatar
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    Re: Need Help with HDR

    Quote Originally Posted by pono View Post
    I used the HDR function on CS3, and I think I had about 5 shots, shot on a tripod, but when the program merged all the photos, they weren't lined up correctly. For example, th subject was shown multiple times in different parts of the frame, with the different exposure rates.
    Any suggestions?
    Hand holding the camera is even more difficult, especially if there is vertical movement of the camera. Even with a tripod you might get some movement unless you use a remote shutter release.

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