Number of bracketed shots for HDR

Discussion in 'Nikon' started by barry clemmons photography, Feb 22, 2013.

  1. I have started doing a little more HDR photography, especially with my landscapes. I am wondering how many bracketed shots other people feel is necessary for optimum results. In doing some research I have read the "more is always better" argument in favor of nine shots, but since I have started shooting with a D800E that means almost 500 MB for each. That eats up memory cards pretty quickly if I am out shooting for the day. I recently did a little experiment with a landscape where I had taken nine shots with one stop between each. I then used Nik HDR 2 to process using all nine, then seven, five and finally three shots. What I found surprised me a little. I found that, at least for that scene, that five looked best to me. Using nine and seven shots took away some detail from the clouds in the particular scene while not handling shadow details in the trees significantly better than five. Three was least pleasing to my eye although it too was very good. One of the complaints from some D600 users has been that it will take a maximum of only three shots using the BKT function. I know that it is "in the eye of the beholder", but I was just wondering how many shots others are using for HDR photography.
     
  2. As a general guideline, one wants to pick the two endpoints that (1) cover all highlights without blowing them, and (2) reach far enough into the shadows that your final rendering will not show blackpoint clipping where you don't want it.
    There's definitely no need with a modern camera to use 1-stop bracketing. With a D800/E, you can use between 2-3 stop bracketing. The important thing is your choice of the longest and shortest exposures. The total number of shots needed is only enough to cover the dynamic range in between them.
    As you suggest there's a point of diminishing returns. Optical and electronic aberrations can be exaggerated. And time is a cruel master in more ways than one.
     
  3. I'll second Luke's assessment. Only two frames should be needed as long as the required dynamic range is covered, and that the extended range doesn't exceed the camera's basic 12 stop range. However, Luke is incorrect in saying that the D800/E can be set to a bracketing interval greater than 1 stop; the maximum interval between bracketed frames is only 1 stop. Therefore you have to take as many bracketed exposures as the number of extra stops needed, and this is limited to 9 stops. Nine stops should be plenty for any HDR project, but having to take 9 shots to achieve it isn't sensible, and takes time; during which the light might change or the subject move substantially. (It's to be hoped that Nikon can address this quite severe drawback in a future firmware update.)
    Of course, if you're happy with JPEG only output, a 3 stop "differential" and the way that the camera processes the shots, then HDR is available direct from the camera. I think this lame and limited set of options show that Nikon really don't understand the nature or purpose of HDR shooting.
     
  4. Luke and RJ, thanks for your input on this. The new D7100 shows that it can be set to bracket up to 3 stops with a maximum of 5 shots for a limit of 15 stops. I really wonder why Nikon didn't give the D800/E the ability for at least 2 stops between shots. I haven't tried the in-camera HDR because of what RJ pointed out.
     
  5. ``I found that, at least for that scene, that five looked best to me. Using nine and seven shots took away some detail from the clouds in the particular scene while not handling shadow details in the trees significantly better than five.``
    Barry, an important consideration is that the blend ratio should be relative to the bracketing steps.

    If you shoot in one-stop increments and take 5 shots, the blend ratio, when the photos are layered, should be 100% opacity of the brightest (base) layer, followed by 50% opacity of the next brightest layer (one-stop down), 33% of the third layer, 25% of the 4th layer, and finally 20% of the 5th layer.

    In other words, 100% of the brightest, 1/2 of the 2nd, 1/3 of the third, 1/4 of the fourth, 1/5 of the 5th, etc.

    Of course one would finally adjust the flattened layer o taste.
     
  6. RJ, I did not say anything about using auto bracketing. I'm only too aware of Nikon's ridiculous limitations on that. For years, I've done my HDR bracketing with a quick finger on the command dial.
    Also, I did not say that only two frames were needed. I said it was important to pick the two endpoints, and then the number of shots would be determined by the distance between. Two stops have always been a safe interval, but between 2-3 stops should be just fine for a low noise camera like the D800.
     
  7. Joel Grimes who's background style is based on HDR, moves the shutter dial manually counting the clicks then activates the shutter with a remote. I dont follow camera specs too closely, but does that camera really have a 12 stop range instead of 6-8?
     
  8. I would never try and blend an image with a 2 stop difference, 1 maximum.
     
  9. Bob, actually according to DXO testing the D800/E cameras produce a range of 14.4 Evs when shooting in RAW. The new D600 isn't far behind at 14.2.
     
  10. ShunCheung

    ShunCheung Administrator

    Simon, why wouldn't you attempt HDR with two-stop increments?
     
  11. Simon (and Michael Chang) might be talking about actual "blending" which is just a subspecies of HDR. It's a good way to handle some situations where one might otherwise use a GND. But I don't think this is what Barry is doing.
     
  12. I've never found the results very pleasing Shun with 2 stop exposures over, as odd as this might sound and I don't HDR very often I slightly underexpose my normal exposure and then go a stop either side of it. We have so much latitude with these cameras that I don't think we need to go the full extremes.
    I have often found the 2 stops over frame problematic (highlights) and don't bother with it anymore.
     
  13. Simon, it still sounds like you're talking about "blending" as in layer blending in photoshop. And in that case, I could see good reasons for doing what you're doing. But in the case where one is generating intermediate files, e.g., OpenEXR files, in floating-point space, followed by tonemapping, I don't see where the issue is in 2-stop bracketing.
    I also think that the success of the blending method (or the tonemapping method) also depends upon what kind of tone curve one is using. Blending files of differing exposures that all use the "normal" (in Nikon terms) tone curve would involve an awkward combination of the shoulder of one exposure and the toe of another. I always do HDR captures using the "linear" or "neutral" tone curve to get the smoothest first-order data.
     
  14. Luke, can you go through your process to create HDR images? In other words from capture through processing, including the software you use. Let's assume it is a landscape image with with bright highlights in the sky and deep shadows in trees.
     
  15. For any given situation, tools and methods may differ somewhat. For a landscape image of the kind you're describing, a blending process might even be the method of choice. But there are some guidelines that are worth keeping in mind.
    1) Determine the high and low exposure limits as described above. Shoot at 2-stop intervals to cover the range between the high and low limits.
    2) Capture to 16-bit TIF using the "neutral" (NX) or "linear" (C1) or "camera linear" (LR) profiles to maintain the linearity of the dataset and the accuracy of interpolation. Apply WB equally. Turn off NR and other enhancements. I recommend avoiding embedded RAW processing in the HDR tools themselves, which are provided only for convenience.
    3*) Using the tool of choice, make an HDR file, e.g., an OpenEXR, then tonemap. Perform additional post-processing in photoshop.
    As many tools have developed and will develop, the choices will vary. Some tools may have improved methods for maintaining color accuracy throughout the process. Some may allow one to edit in 32-bit space. Some may have better methods for relighting, smoothing, and detail enhancement. This is a matter of judicious choice.
    I recommend the HDRI Handbook, 2nd Ed. by Christian Bloch. This is a new and completely rewritten edition that is just out in the last two months. It has some very up-to-date information and is suitable for industry f/x professionals as well as photographers.
     
  16. Luke, thanks so much for your explanation. I had purchased "The HDR Book" by Rafael Concepcion when I first started researching HDR, but will also take a look at the book you suggested. I prefer the HDR image that has a more natural look, but from time to time I have experimented with the high saturation rich color look as well. My wife likes the highly "structurized" HDR image that looks more like a painting. As I said above, it is in the eye of the beholder.
    I have been doing photography for over 30 years but learn something new every week. I have probably learned more reading this forum and the input from the many participants in the last few years than I did in the first 20 years of teaching myself. I loved shooting film, but I have to admit that digital photography has stimulated the creative part of my brain far more. I know that will be blasphemy to some. :)
    Thanks again for your explanation, and for the input from everyone else as well.
     
  17. Luke I am talking about HDR using Photomatix and not the exposure blending. To be totally honest I won't use the colorspace in that programme, I will use most of the presets at the very minimum and usually convert the finished file to black and white. All these bracket counts and spacings depend on what you are shooting anyway, I find the HDR process to be very unpredictable so I only do it once in a while.
    If I am outside and use an exposure 2 stops over, it will often blow the cloud highlights, which I just don't like doing, this is with 3 exposures. I am pretty sure this was a 3 bracketed shot, I shot it 3 stops apart as I wanted some definition in the clouds, I could have done this in Photoshop anyway with a single exposure but covered my bases.
     
  18. I am new to HDR. I dont have any software like Photomatrix etc.So , I want to use PS6, LR3/4,or Canon DPP.
    PS6, Canon DPP has HDR feature built in, not sure about LR. I dont know how useful these are for HDR when compared to Photomatrix etc .special softwares.
    Can anyone give advice to make HDR with thesePS6, LR3/4,or Canon DPP softwares!
     
  19. Thakur select the exposures you want to use in Lightroom and then there is an export tab to Photoshop
    Photo/Edit in/ Export to HDR Pro. It's very straightforward.
     
  20. Simon, really nice work! In your case, I'd say you're computing the endpoints just as I'd say, and it just happens to be that this is the number you need -- just enough to cover the highlights and shadows for your intended rendering. Again, really nice work.
     

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