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Old Sep 9, 2009, 2:41 AM   #1
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Default exposure bracketing/hdr for night shots w/ motion?

Ive been interested in HDR lately, and looking at night HDR shots as well. Ive seen a lot of threads with info on night shots and night hdr shots but there is one area I'm not quite sure how to handle.

night shots with motion (such as people walking around, cars moving, etc etc)

I understand if there is no motion it doesn't matter how long the shutter speed is. But if there is motion and you have a 2+ second shutter speed I don't see that turning out very well.

How would you handle this situation as far as camera settings go? I usually do my 3 bracket exposure with an Aperture Priority but it has always been in the daylight so even with motion I can still get fast enough shutter speeds to avoid motion.

If it matters. I have the Sony A700 with the kit 18-70 lens (I know, not the greatest lens, but its what I have for now)

Thanks!
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Old Sep 9, 2009, 9:42 AM   #2
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If you are able to get your shutter speed fast enough to reduce blur in one or more frames to an acceptable level, it might be possible. The Photoimpact HDR routine allows for masking out such things, and possibly other HDR software also. Other than that, you might be able to edit out elements which would cause difficulties, before doing the HDR rendering.

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Old Sep 9, 2009, 9:49 AM   #3
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Well.. if your shutter speeds are not fast enough to freeze movement (and they normally would *not* be for night images), you're going to have motion blur.

You can use a brighter lens (with wider available apertures, represented by smaller f/stop numbers) to help you get faster shutter speeds. But, then you may not have as much depth of field as desired, and you still may not have shutter speeds fast enough to freeze much movement.

You could also use a higher ISO speed so that your shutter speeds are faster. But, that will result in higher noise levels, which is undesirable.

There's really no good solution for freezing movement at night, unless you can add light (and you could use second curtain flash to freeze the movement of closer subjects after the shutter was open long enough to expose the background).

Even for one photo at night, you're going to have issues with blur from subject movement. With more than one photo, those issues are going to be compounded.

So, you may just want to accept that you can't expect to freeze the movement of moving subjects at night and look for positives associated with the motion blur (light streaks in the image from vehicle headlights, blur of moving subjects adding a feel of motion to the images, etc.).
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Old Sep 9, 2009, 12:43 PM   #4
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Try this (Sigma 30mm f/1.4). Note that it is designed for cameras with an APS-C size sensor, so keep that in mind if you may buy a full frame Sony model like the A850 or A900 at some point:

http://www.sigmaphoto.com/lenses/len...00&navigator=6

It's around $439 at vendors like B&H:

http://www.bhphotovideo.com/c/produc...1_4_EX_DC.html

Otherwise (you want a lens that will let you shoot at full resolution with a full frame model), I'd look at a used Minolta 28mm f/2, 35mm f/2, or 35mm f/1.4 AF lens instead. Or, look at the Sony 35mm f/1.4G (same as the Minolta 35mm f/1.4G).

I've got the Minolta 28mm f/2 AF lens and it works well wide open (but, if lighting permits, stop it down to around f/2.5 or f/2.8 instead for even better results).

I'd use f/2 as a starting point with the lens you get, depending on what kind of shutter speeds you see (using as high of an iso speed as you can tolerate for the print sizes needed, to get the fastest shutter speed possible for the lighting if you want to minimize blur from subject movement). I'd try ISO 3200 at f/2 and see what you get. Take some at ISO 1600 and ISO 4000, too.

Shoot raw or raw+jpeg.
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Old Sep 10, 2009, 1:26 PM   #5
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Another way to handle night scenes and people is to slow your shutter speed way down for all of the frames. A person moving fast won't appear in the picture (try it for midway/amusement rides, it's fun) and you'll get the streaks of light instead of cars - the street will appear to be empty. That won't work for people who are standing still, though, or moving slowly enough to appear as ghosts. This wouldn't work for all situations, but it's interesting to experiment with.
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Old Sep 12, 2009, 2:52 PM   #6
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Thanks for all the input. Seems like I have a couple option to experiment with, and sounds like getting a faster lens needs to happen as well. Which is fine because I have wanted one anyway, Just need to decide on a 28, 30, 35 etc..
I will play with some results and look at lens options and see what I can come up with.
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Old Sep 12, 2009, 3:38 PM   #7
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All good advice here, but keep one thing in mind. Youre shooting digital NOT film. When you add film cost and processing, each photo cost at least a buck. Now the cost is down to pennies. Shoot, shoot, and shoot some more. If in doubt shoot again. Another big benefit we have now is the lcd screen on all our cameras. If it doesnt look right, then delete and shoot again. This is not to say that learning the principles of photography isnt necessary. If you learn what you are doing then you will be shooting less and thus saving some time. But until then pay attention to what you are doing and show us the results.
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Old Sep 13, 2009, 10:43 AM   #8
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Quote:
Originally Posted by JimC View Post
...
You could also use a higher ISO speed so that your shutter speeds are faster. But, that will result in higher noise levels, which is undesirable.
...
Elevated ISO's also significantly reduce the tonal range of any single image, often several stops. This totally negates the purpose of HDR.

There is one way of avoiding problems with moving people and vehicles, provided they don't move too far during the exposure. I've not done this with HDR shots but have for single shot images either at night or when shooting stereo pairs with a single camera.

The trick is to take several pictures (2-4) at each exposure setting. You then stack each set with matching exposures and edit by erasing or using Layer Mask to hide the moving objects and reveal background from a differnt shot taken when they had moved elsewhere in the image. It's the reverse of the trick where you layer several images where one person has moved to a different chair in each shot and you want a final image with that one person in each chair. When you get the set of bracketed shots with all of the moving objects removed you stack them for HDR processing.
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