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Author Topic: HDR bracketing  (Read 4052 times)

stamper

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HDR bracketing
« on: August 09, 2010, 11:18:10 am »

I have been looking at the bracketing feature on the D700 to take images for HDR. With bracketing 1 stop apart and a series of three is it best to spot meter for the sky and lock exposure with +1.7 EV and take three shots ( + 3 or - 3 ) or should I be regarding the middle shot as a mid tone in regards to exposure? I tried the latter but wasn't happy with the results. This involved + 1 and - 1. In reality the mid tone is hard to achieve. I usually take my landscape images using the first method. I am using Photoshop CS5 and the HDR merge function. TIA
« Last Edit: August 09, 2010, 11:19:39 am by stamper »
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Peter McLennan

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HDR bracketing
« Reply #1 on: August 09, 2010, 12:49:23 pm »

I aim for slight overexposure in the center image while ensuring that the underexposed image shows zero highlight clipping.
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feppe

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HDR bracketing
« Reply #2 on: August 09, 2010, 01:00:07 pm »

Quote from: stamper
I have been looking at the bracketing feature on the D700 to take images for HDR. With bracketing 1 stop apart and a series of three is it best to spot meter for the sky and lock exposure with +1.7 EV and take three shots ( + 3 or - 3 ) or should I be regarding the middle shot as a mid tone in regards to exposure? I tried the latter but wasn't happy with the results. This involved + 1 and - 1. In reality the mid tone is hard to achieve. I usually take my landscape images using the first method. I am using Photoshop CS5 and the HDR merge function. TIA

I wouldn't get caught up with which one is the middle shot. I don't work with "true" HDR so my shooting for blending method might not work for you: I shoot 3 bracketed exposures, one ETTR, one +2 EV, one +4 EV (why four stops). Easiest way to achieve this is to set exposure compensation to +2, and bracket three shots at 0, +2, -2.

BobFisher

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HDR bracketing
« Reply #3 on: August 09, 2010, 02:07:24 pm »

The goal, with HDR, is to capture the full brightness range of the scene in front of you.  Don't get hung up on 3 shots or 4 or 5.  Concentrate on capturing the full range of brightness regardless of how many shots it takes.  If that's the full 9 that the D700 is capable of, so be it.  Unfortunately, Nikon has limited the spacing to 1 stop on the D700 in AEB so you may have to take more shots than you otherwise would with a Canon or other camera (or some other Nikons) that will allow 2 stop spacing.

The D700 has a spot meter.  Make use of that.  Meter your bright spot and your dark spot, figure the difference between the two and that'll tell you how wide you need to bracket.  Shooting in Manual mode, the D700 doesn't 'bracket' like in Av or Tv, rather it starts at the set exposure and increases exposure from there.  Set your shutter at the fastest speed (for the brightest spot) and tell it how many shots to take.  It'll then move from the fastest to the slowest (for the darkest spot) in sequence.  While testing shows you can get up to about 11 stops in ideal conditions, I'd consider 7 to be the practical limit.  If the meter tells you you've got a 12 stop difference, then you'd want to take 5 shots at 1 stop intervals.
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stamper

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HDR bracketing
« Reply #4 on: August 10, 2010, 04:18:17 am »

Quote from: feppe
I wouldn't get caught up with which one is the middle shot. I don't work with "true" HDR so my shooting for blending method might not work for you: I shoot 3 bracketed exposures, one ETTR, one +2 EV, one +4 EV (why four stops). Easiest way to achieve this is to set exposure compensation to +2, and bracket three shots at 0, +2, -2.

This is what I think may be best but not sure. I did try the +1,  0,  -1, and the EV at - .07 I then exposed for what I think was a mid tone. This meant that the middle one's histogram was touching the right hand side and the +1 was over exposed. Again not sure it was best. I have read a lot of articles on HDR - even bought a book - but they don't mention bracketing, possibly because of the different makes of cameras involved and their implementation of bracketing. At the moment I am trying to do this hand held - I know it isn't best - so the link provided doesn't really apply? In my first post I mentioned locking exposure at + 1.7. Would this be considered to be ETTR?  

Lightbox

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HDR bracketing
« Reply #5 on: August 10, 2010, 04:47:54 am »

First get yourself a tripod if you want to do any serious HDR images, I actually work the opposite way to what Peter mentioned above, and shoot at least 5 images 1 stop apart. If you think about it, in a finished image that you would send to print, it would be better to have slightly darker shadows than to have blown highlights. So I start with a base exposure that is slightly underexposed and bracket up and down from that, this way you've got slightly more information in your range of images towards the highlights. Most scenes are different though and may not need bias towards the highlights if there ain't any bright sunny clouds.
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BobFisher

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HDR bracketing
« Reply #6 on: August 10, 2010, 07:30:53 am »

Keep in mind, even if your camera only permits 3 shots in a bracket, you can always get more.

You can bracket manually by establishing your base exposure, shooting in Manual mode, calculating your end points, starting at one end point and adjusting the shutter speed between shots.  You have to have a tripod or some form of support for this.  Handheld isn't going to work.  It means touching the camera, which means some potential for camera movement but if you're careful, you'll be fine.  This is what I used to do when I shot Canon.  It takes a little more time but it works.

You can also do it by dialing in exposure compensation.  Working in Av, get your base exposure, set up your bracket, then apply either +ive or -ive exposure compensation.  Take your 3 shots then dial in the opposite exposure compensation and take your 3 shots.  You might have an overlap so just toss out the overlapped shot(s) when you do the merge.  Again, a tripod is needed for this.

Lightbox is right about getting a tripod.  Unless your camera shoots at a high frame rate and your shutter speeds are fast enough to take advantage of the high frame rate, you're going to have alignment problems.
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stamper

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HDR bracketing
« Reply #7 on: August 10, 2010, 07:59:43 am »

Quote from: BobFisher
Keep in mind, even if your camera only permits 3 shots in a bracket, you can always get more.

You can bracket manually by establishing your base exposure, shooting in Manual mode, calculating your end points, starting at one end point and adjusting the shutter speed between shots.  You have to have a tripod or some form of support for this.  Handheld isn't going to work.  It means touching the camera, which means some potential for camera movement but if you're careful, you'll be fine.  This is what I used to do when I shot Canon.  It takes a little more time but it works.

You can also do it by dialing in exposure compensation.  Working in Av, get your base exposure, set up your bracket, then apply either +ive or -ive exposure compensation.  Take your 3 shots then dial in the opposite exposure compensation and take your 3 shots.  You might have an overlap so just toss out the overlapped shot(s) when you do the merge.  Again, a tripod is needed for this.

Lightbox is right about getting a tripod.  Unless your camera shoots at a high frame rate and your shutter speeds are fast enough to take advantage of the high frame rate, you're going to have alignment problems.

You are both correct about the tripod, but it isn't always handy to use. If you were on the streets of Glasgow, Scotland, you wouldn't want to be using one. I was jostled last week by crowds when I was taking hand held shots for HDR never mind using a tripod. You are correct about dialling in EV exposure. I very rarely take images without using EV exposure normally so when taking some for HDR then it must be used? No consensus of opinion seems to exist as to how much which I suppose is to be expected. Photoshop CS5 has a ghosting function to eliminate alignment in Merge to HDR.  Can the align feature - I haven't tried it - not be used to align layers. This would of course mean using TIFFS instead of RAW.

BobFisher

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HDR bracketing
« Reply #8 on: August 10, 2010, 09:00:57 am »

Yes, there are circumstances where a tripod isn't practical.  But where it is, using one is better than not using one.  I set up tripods on the streets of Toronto all the time.  No problem.

You're misunderstanding the use of Exp Comp as I'm suggesting it.  Using exp. comp. to adjust the metered exposure for the built in bias (with most matrix type meters now this isn't necessary in many circumstances; they're that good) is different from using it to create a wider bracket sequence.  And no, I wouldn't suggest using exp. comp. to adjust meter bias when doing HDR.  As noted, today's multi-segment meters are so good that it's generally not necessary and shooting in Manual you set the exposure where you want it anyway.  What I'm getting at with using exp. comp. in bracketing is to use it to get a wider bracket.  For example, you've got your camera set up to do a 2 stop bracket (-2, 0, +2).  If you dial in -2 exp. comp. and take one sequence you're going to get -4, -2, 0.  If you then dial in +2 exp. comp. and take a second set you're going to get 0, +2, +4.  Toss out one of the 0 shots and you've got a nice 5 shot bracket with, in almost all cases, enough exposure to cover the entire scene.  Same thing applies if you're doing a 1 stop bracket (-1, 0, +1).  Dial in -2 and you get -3, -2, -1.  Dial in +2 and you get +1, +2, +3.  No zero shot?  Not really a big problem but you can shoot the single 0 shot before you start the brackets or after you're done.

Sure, the align functions of most HDR software apps are quite good.  But if the input shots are misaligned, you're going to have, at the very least, problems at the edges and there may be a need to crop.  If you've got rotiation rather than just vertical/horizontal movement the problem is exacerbated.  Shooting a bit looser composition will make up for that (horizontal/vertical movement) but you're throwing pixels away.  The deghosting process of some HDR software doesn't make up for misalignment.  It's intended to make up for things that may be moving during the shot in the scene, not for camera movement.  Some are better than others but none are perfect.  And no, you don't need to use TIFFs for the align functions of HDR software to work.  The Align Layers function in PS is different.  That's not what's used in aligning input shots in HDR Pro.
« Last Edit: August 10, 2010, 09:04:14 am by BobFisher »
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stamper

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HDR bracketing
« Reply #9 on: August 10, 2010, 10:49:02 am »

Thanks for the feedback

Quote

You're misunderstanding the use of Exp Comp as I'm suggesting it. Using exp. comp. to adjust the metered exposure for the built in bias (with most matrix type meters now this isn't necessary in many circumstances; they're that good)

Unquote

I don't think I agree about adjusting metered exposure on modern SLR'S.  First up I don't use matrix on my Nikon D700 or D300. Should I be using it whilst shooting for HDR'S? This is where I might not be understanding the correct procedure? I understand about your assertion about EV 2 stops apart which I have tried without a tripod and isn't suitable. What I am really trying to understand is the metering when bracketing shots, whether to underexpose or overexpose or try once again for a midtone and do 1 or 2 over and 1 or 2 under with 0 set to the midtone or the -3 or + 3 exposed for a highlight or even a shadow area with suitable EV compensation.
« Last Edit: August 10, 2010, 10:50:57 am by stamper »
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BobFisher

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HDR bracketing
« Reply #10 on: August 10, 2010, 11:22:51 am »

For some reason I thought you were shooting Canon.  

It's a little different for the D700/300.  You're far less hamstrung with those cameras.  You can only shoot at 1 stop intervals (unless you've discovered a firmware hack and if you have, I'd be pleased to know about it   )but you can shoot up to 9 shots (+4 to -4).  You've also got the fast burst rate which is very helpful shooting handheld.

Yes, I would use the matrix meter.  I do.  As I noted, it's good enough that I don't use the internal spot meter except to check my brightness range to know how many stops I need to bracket.  And the only time I might dial in some exp. comp. for a single shot is in the case of a scene that was very bright or very dark overall.  And even then the matrix does a pretty good job.  

Try using the matrix metering system and bracketing around that metered reading.  I think you'll find it does a very good job for you.  For times when I may want to deviate from the matrix reading, I still carry a handheld meter to take incident readings then shoot in Manual.  
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