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hdr?

Discussion in 'Photography, Art & Design' started by Teyber, 6 Feb 2008.

  1. Teyber

    Teyber ******

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    hello!
    Question... in another forum, there was a thread on posting HDR pictures. Im assuming that hdr is high dynamic range lighting correct? the only HDR i have seen is that in video games, which looks very different from this. Could someone link me to a tutorial on taking HDR shots? im not sure if its on the editing or on the camera side of things. Quick google search gives me nada. Mom mas a dslr that isn't used most of the time, (she uses it lots, but 95% of time i can use it when i need). Sorry for noob question, i hope this makes sense.

    regards
     
  2. Firehed

    Firehed Why not? I own a domain to match.

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    You don't "take" HDR shots - you need to take multiple exposures and merge them together using any number of tools. It depends entirely on the scene, but generally you would want to take a shot at 0EV with evaluative (full-scene) metering, a +1EV/+2EV and a -1EV/-2EV. Ex. if ISO100 1/100s f/8 is 0EV, also take a shot at 1/50s f/8 and 1/200s f/8 to get a stop more and less exposed respectively. A lot of cameras, especially SLRs, have an auto-exposure-bracketing feature built in, just in case you can't be bothered to fiddle with a dial.

    Important things to note:

    Use a tripod! Photoshop and several other tools that can make HDR shots can also do some alignment, but it's really best if the scene is identical across all of your shots other than the lighting.

    Only change your exposure time, or ISO if you absolutely must. Changing the aperture is going to mess with your depth of field and you'll end up with a really screwy composite image.

    There's a LOT of "merge to HDR" software out there, but in my experience you're best off just aligning things in Photoshop and then use layer masking to change the exposures. The automatic stuff really never gives satisfying results whenever I've tried it.
     
  3. planzz4

    planzz4 New Member

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    Photomatix have a free trial of their HDR compositing software which is functional enough for you to see if its of interest for you. Just make sure to double check the instructions as at one stage (prior to tone mapping) it looks as if its all gone wrong!
    While a tripod will help you can perfectly well hand hold at least while your getting a feel for the effects obtainable.
     
  4. mushky

    mushky gimme snails

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    It's automated in Photoshop.. File > Automate > Merge to HDR or something like that.

    If you shoot in RAW its easy enough to use just one picture that you have changed the exposure on to make 3 images. It works better if you have 3 bracketed exposures.
     
  5. planzz4

    planzz4 New Member

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    I don't think photoshop elements does HDR merge so it would be much cheaper to get a specialised hdr package than the full PS.
     
  6. mushky

    mushky gimme snails

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  7. Firehed

    Firehed Why not? I own a domain to match.

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    You CAN do it with one RAW image, but you're really simulating details at that point. It's not as bad as just messing with the brightness/levels in a JPEG, but it's still not nearly as effective as separate exposures. Just pretend that it's not an option :)
     
  8. Teyber

    Teyber ******

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    thank you all so much!

    Sorry about noob question. I read a couple guides at www.good-tutorials.com and also the one mushky linked, and i get the hang of it now. I have photoshop ps2 btw, so i can just merge to hdr. i will try just layer mask however. I havn't really had a lot of time in my life where i want to get into photography (just turned 16 here...), but seeing some very unique pictures lately have wanted to get me into it. I don't know very much about exposer/f-stops ( i know what they are, but not enough to play with it...), so autobracketing should be nice. Im not positive the canon rebel xt has it, but my guess is it does.

    Also: i don't really understand RAW at all. How can you make 3 pictures with different exposers and focuses with 1 picture? thats what it applied in the tutorial i was reading...

    Is RAW how you get those pictures that change pictures? idk how to explain it, but lots of peoples sig's have a picture, and it merges to another one, and so on. Is this how you do it?

    regards

    p.s. thanks so much for help!
     
  9. planzz4

    planzz4 New Member

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    raw format is the raw data taken from the camera sensor. Because it hasn't undergone any lossy compression or even been interpreted into an image we can see you have more latitude to adjust the apparent exposure without clipping. It depends on the picture but +/-1 stop can be generally be done without obvious artifacts.

    In your tutorial the focus won't have changed (and musn't for HDR to work) just the apparent exposure. In reality there won't be as much information there as from 3 pictures but you get something of the effect.

    The moving pictures are animated gifs I think nothing to do with RAW.

    (most cameras record 3 colour 'pixels' slightly off set which then have to be turned into a picture by raw convertor software. If a camera only has a jpeg setting this is done automaticaly in the camera, slr's give you the option to gain more control by doing this your self.)
     
  10. mushky

    mushky gimme snails

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    Rebel XT definitely has auto bracketing. Look in the menu for AEB. If you then select continuous shooting it will take all 3 pictures if you hold the shutter release down. You can shoot in JPG if you do it this way.
     
  11. Da Dego

    Da Dego Brett Thomas

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    But ya shouldn't ;) Good habits, good habits. Shoot RAW - it gives you 12bpc instead of 8 - which is even nicer when stitching HDR. ;)
     
  12. Firehed

    Firehed Why not? I own a domain to match.

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    It's good in principle but doesn't mean anything in practical terms right now for any screen work. Maybe CMYK print work can make more effective use of the extra color resolution.
     
  13. Teyber

    Teyber ******

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    But if i do the auto shutter release, then won't the exposure be the same for every one?
    i was thinking focus because i saw a picture of a harbor, with several pictures focused at each of the different aspects in the picture. It was really trippy...

    Thanks for all the noob help. I will try to get out and practice afterschool today.

    Regards
     
  14. ajack

    ajack rox

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    If you set it to continuous drive and have bracketing set then it'll take all 3 differently exposed shots one after another.
     
  15. Da Dego

    Da Dego Brett Thomas

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    It's not about that, it's all about the approximations. :) 12bpc in your computations is considerably better - then the tone mapping gets applied and fixes it down to the monitor resolutions or print resolutions. But you get the most accurate and faithful representation possible - After all, eventually displays will improve.
     
  16. supermonkey

    supermonkey Deal with it

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    That's true in theory; however, in practice a 12-bit image can produce greater dynamic range than an 8-bit image. An image captured in 8 bits will only capture 256 shades of gray. those 256 shades will map directly to a computer monitor. When an image is captured in 12 bits, it effectively captures 4,096 shades of gray. Software allows for the "best" 256 shades to be mapped to the monitor. By selecting an ideal range we are able to get more detail in the darker shadow areas.

    Using 12 bits makes a lot sense, especially in scientific applications where quantitative image analysis is important. If you're going to be doing HDR, then you want to get as much detail in your image as possible, and shooting RAW to get the full 12 bits will help get as much tonal range as possible.

    Of course, it is estimated that the human eye can only distinguish about 64 shades of gray, so maybe even 8 bits is too much. :)

    Edit: forgot to add this article that explains it better than me.

    -monkey
     
  17. mushky

    mushky gimme snails

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    Well ideally shoot EVERYTHING in RAW for that reason, but it's just not necessary sometimes. Especially for someone who is asking what RAW is.
     
  18. Teyber

    Teyber ******

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    alright, i cannot find the Autobracketing feature... :p Would it be in the menu? any other names it would go by?

    regards
     
  19. Firehed

    Firehed Why not? I own a domain to match.

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    It should be called Auto Exposure Bracketing, though it may be listed as just 'AEB'.

    And I withdraw my point about 12bpc. IIRC, Bit even did an article on that kind of thing a while back, though it was more along the lines of 6bpc vs 8bpc monitors.
     
  20. ajack

    ajack rox

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    It'll be in the manual. Otherwise a very quick google came up with this.
     

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