What is HDR?

Discussion in 'Digital Photography' started by Kardashian, May 25, 2007.

  1. Kardashian macrumors 68020

    Kardashian

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    #1
    I've been looking around on Flickr for some pictures of Brisbane.. just to get a taster of whats to come when I go there for 6 months in December, and I noticed a lot of really beautiful, vibrant photo's. Upon opening them, everyone has left a comment saying ''Beautiful use of HDR" or something similar.

    What is this HDR?

    I searched on Wiki but it didn't make much sense to me... :eek:
     
  2. Doylem macrumors 68040

    Doylem

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    #2
  3. Martin C macrumors 6502a

    Martin C

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    #3
  4. M@lew macrumors 68000

    M@lew

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    #4
    You could think of it as getting all the details of a photo into it without glare or too much/little light. That's a very VERY basic explanation I think. I'd have probably missed out on a lot of details but it's the best I've got atm. :)
     
  5. compuwar macrumors 601

    compuwar

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    High Dynamic Range is just that. All visual mediumes have dynamic range, that is a continguous collection of levels of light that will resolve to something. In photography, we measure light in "stops," each stop being half or twice as much light as the previous or next stop in the list[1.] So, let's say you have a scene that's best represented by 10 stops of dynamic range, that is there are 10 levels of light between the detail in the deepest shadows where we want it to not be pitch black and the brightest highlight where we don't want it to be plain white. Now let's say our camera's sensor has 5 stops of dynamic range[2]- one photograph won't cover the entire scene's dynamic range. Simplistically, two shots, one with the exposure set so it covers from the low end to the middle, and one from the middle to the high end will cover the entire scene. With HDR, you then blend those two images together to cover the entire range. Many HDR images look "plastic" because the tonal range is much larger than we'd see in a normal image.

    [1] Which is why (amongst other things) f/2.8 lenses are more expensive as f/4 lenses, they can work in half as much light.
    [2] Sensor dynamic range can vary with ISO, it's not necessarily a static thing.
     
  6. Lovesong macrumors 65816

    Lovesong

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    #6
    Compuwar pretty much explained it. If you happen to be a visual learner, then here:

    In photography we are often confronted with situations where we have high contrast between 2 areas. A single image from a camera in that instance will either capture the highlights and underexpose the shadows, or will blow out the highlights, and capture the shadows. The first 2 pictures demonstrate this. The idea behind HDR is to intentionally capture just one area of the image, and then cobine it with other images (using software) so that the entire scene is properly exposed: ie picture 3.
     

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  7. epicwelshman macrumors 6502a

    epicwelshman

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    #7
    I'm not sure how I feel about HDR. When I first learnt about it I was all for it. Now, it seems a little gimmicky unless it's done really well, which it usually isn't.

    That being said, are there any free HDR programs (excluding photoshop)?
     
  8. Lovesong macrumors 65816

    Lovesong

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    #8
    I had some issues with it at the begining- I'm more or less a purist when it comes to photography. The way I think about it, and justify it- is that in reallity the HDR is what my eye sees.

    Man, where do I get that optic nerve attachment for the EF mount? :p
     
  9. Westside guy macrumors 601

    Westside guy

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    #9
    Of course "high dynamic range" refers to the original situation - the image end product doesn't really have any higher range in the color space than a normal image does. It's just that two (or more) different parts of the image have been normalized, in terms of dynamic range, independently of each other. That's why IMO the images tend to look fake - your eye just has too much darn dynamic range!

    I'm not a big fan - I've seen much more natural-looking results from people using things like gradient ND filters. But those have trade-offs as well, obviously; and my preferences may be swayed by the relative skills of the practitioners of each method (it's not particularly fair to compare what Galen Rowell or Tony Sweet have done against HDR images posted on a forum).
     
  10. seenew macrumors 68000

    seenew

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    #10
    this is one of those things where film prevails over digital, at least in what I've learned about black and white so far. You can expose your film for the shadow detail you want, develop the film for the highlight details, and then use a filter, or split filters, to tweak it just right. The dynamic range in a traditional photographic print is amazing.
     
  11. compuwar macrumors 601

    compuwar

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    #11
    That's heavily dependent on the color gamut and dynamic range of your output medium, as well as what file format you can get to the output medium with. If you're printing from a TIFF onto a relatively high-range medium then you're likely to see a tonal graduation difference at both ends of the spectrum versus an 8-bit JPEG file. A screen really isn't the "right" way to critically view an image, as it's very limiting.

    It's not all that amazing. People have started to wax philosophically, but we're at the point where digital sensors are getting to about the same as color print film and with HDR you can reproduce the dynamic range of most B&W film. Shooting digital is like shooting positives, you expose for the highlights and let the shadows fall where they may, but you get back shadow detail with HDR- all the tweaking happens in PS, but there's a lot of room in an raw file for tweaking too.

    I think a lot of the issue is that people are comparing analog prints to what they see on a monitor, not to analog prints- and that'll always foul things up.

    If you look at sites like:

    http://www.dantestella.com/technical/dynamic.html

    You'll see 9.5 stops of DR for the good (old) D2x, if you do a full auto-bracket at 1 stop increments, you'll get seven additional stops of data, putting you at 16.5 stops. That's only half a stop under the TMax 100 DR, while the base is over Kodachrome 25. Without an iris change, your eye is at 7 stops- since an image isn't just about contrast range, and since digital doesn't shoulder and toe like reversal film, you can't do a pure apples-to-apples comparison, but digital compares very favorably overall and the post-shooting manipulation is *so much easier* too! Not to mention the fumes, chemical disposal...

    Frankly though, the other piece of the puzzle is flexibility. If you look at the following link:

    http://www.imaging-resource.com/PRODS/D2XS/D2XSIMATEST.HTM

    They're touting acceptable 13x19 prints at ISO 1600 from a D2xs- which if you listen to the measurebators, is completely unacceptable past ISO 400. To get a clean 11x14 off of print film from a 35mm sized body at ISO 1600 wasn't all that easy. Heck, I rarely shot 645 above a base ISO of 800 (Ilford Delta 3200 at its "natural" ISO processed in PMK was my usual "high speed" B&W solution, 645 if I could, otherwise in 4x5.)

    While we're not quite at parity with B&W, the only place you really lose with digital is against alternative processes. In color though, I think it's at least parity- I've got 16x24s hanging on the office wall that have incredible detail, I can't remember ever wanting to go above 11x14 from small-format positive or reversal film.
     
  12. seenew macrumors 68000

    seenew

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    #13
    I'm no film purist; quite impartial. I'm just saying that you can get much more detail in highlights and shadows with one film shot (with the right processing) than you can in one digital shot (even with processing). HDR requires multiple exposures. Although, split filtering in film printing could be argued to be the same thing...
     
  13. Westside guy macrumors 601

    Westside guy

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    #14
  14. compuwar macrumors 601

    compuwar

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    #15
    I'm pretty sure that 15 stops is with your iris changing as you look around the scene- but I don't know for sure.
     
  15. zagato27 macrumors 65816

    zagato27

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    #16
    Thanks for the explanation. I just viewed a photograph in another forum that was done in HDR and it was awesome! I've been trying to get more info on the process and this has been great. OK, I'm not a photo geek but I do know what I like and the picture I saw was terrific. Seems like the limitation is that it can only be used for stills as you need a couple of exposures of the same subject. Still, cool. Thanks guys. Cheers
     
  16. faustfire macrumors 6502a

    faustfire

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    #17
    There is a really simple program called Photomatix that makes creating HDRIs really easy.
     
  17. Butthead macrumors 6502

    Butthead

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    #18
    For as much extra DR you want, you must take that many more shots of exactly the same image, can't move the camera one iota. However there are other HDR options like the Fuji S5 Pro still, and some of the newer 4k res video full-frame 35mm format sensors in camcorders like The Red One are supposedly capable of 14 stops DR, but as there are no defined standards of measurements, DR is in the eye of the evaluator...subject to opinion/interpretation of the data

    More, but how much? The Fuji S5 Pro will get 12 stops DR from a single shot if you expose carefully, according to dpreview, but is this always useful in every situation?

    I'm lead to believe (not saying you'd agree, but please state why in detail you think one way or another) by Ken Rockwells review of the Fuji S5 Pro, that you can get that greater DR in viewing an 8bit JPEG image, yes or no?

    Nikon 2Dx is old, but what about ISO setting for the 9.5 stop range (and that site link is from 2003, kind of dated in that the Kodak 14n sensor/dSLR is reputed by some reviewers as being inferior quality to the prior Kodak sensor).

    http://www.amazon.com/Kodak-DCS-14N-13-89MP-Professional-Digital/dp/B000087KUR


    Fuji S5 Pro delievers 12 stop DR, but only at lowest ISO settings, drops quite a bit the higher you go on ISO range.

    Ken Rockwells page on the S5 Pro's supposed advantage in extra DR, shows/concludes that it is not very useful, as compared to proper lighting of the scene, as no sensor can overcome severe ranges of DR, at least not in the examples he's choosing to illustrate with.

    http://www.kenrockwell.com/fuji/s5/dynamic-range.htm


    What is interesting is that dpreview is claiming that the reduced DR at ISO of greater than 1200 is a rarely useful need. LOL, I guess then they only do a limited amount of photography. Try getting that big $$$ shot of Lindsay Lohan outside a night club in the dark shadows, under HPS or HID lighting...yeah, you need Nikon's ISO 24k with a fast lens in those situations if you want a sharp image. Having 15 stops DR in those situations couldn't hurt either.

    http://www.amazon.com/Kodak-DCS-14N-13-89MP-Professional-Digital/dp/B000087KUR

    How about outdoors, wedding shots when even the photographer should know what they are doing and have used fill flash, what say then yee Ken Rockwell?

    http://forums.dpreview.com/forums/read.asp?forum=1021&message=24291058

    I'd say, even greater DR than the Fuji S5 Pro could have made these wedding pictures come out even better. So if this wedding photographer wanted to go through the trouble, probably could have done plus/minus a stop a few AEB shots with subjects standing still, and used HDR software to get greater than 12 stops DR.

    Here's another situation where Ken R. would have been foiled, was a requirement to shoot without flash or no lighting allowed. OMG, what would KR done then to get his shot for the $$$?

    http://ryanbrenizer.livejournal.com/434727.html
     
  18. valdore macrumors 65816

    valdore

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    #19
    Here are some of my recent HDR photos as an example...

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