Combining multiple image

[Matt24138]

I have been looking at photos where I can tell the shutter speed was set different for different areas like a beach shot with no movent but the waves are blurry from the motion. I am sure this is done in post but I am not sure how. All I have is gimp. Is it possible to do with gimp.

 

[analog.universe]

Can you show an example? the effect you describe sounds like it can be achieved with a slow shutter and tripod...

 

[Matt24138]

I can't. I don't want to post someone elses work. Everything is still like a bird in the sky but the waves you can see the movement. With the still flying bird in the sky this leads me to believe it was 2 shots at the same location.

 

[Robin Usagani]

If the bird is far away, it doesnt move much.

 

[Josh66]

You could do it with two shots with different shutter speeds, but the same overall exposure. Using an ND filter for one of them would be best, so you wouldn't have to change the aperture.

Then it's just a matter of merging them together (make sure you shoot from a tripod to make this easier) - and yes, you can do that in GIMP.

 

[Josh66]

The sample picture they have here really sucks for what you're doing, but this is what you'll want to do:
9.2.*Depth Merge

The simple drawing with the blocks at the bottom will probably be more useful than the picture at the top to help you see what is going on...

There are other ways to do it in GIMP, but for what you're talking about, this seems the easiest.

 

[Matt24138]

So I would adjust shutter speed and iso to compensate for difference then overlay it in gimp?

 

[Josh66]

Yes, that would work. Just watch out that the high ISO one isn't so high that it has a lot of noise.

If you have ND filters, that would be the best way. Changing the ISO would be my second choice.

You could also change the aperture, but then the DOF would change, and that would probably be bad for this...


I couldn't find any better tutorials than the one I posted (which kind of sucks...), but it's not extremely hard to do... You might be able to find a better tutorial on YouTube.

 

[Matt24138]

Would I use the filter for the long or short exposure or both?

 

[Josh66]

You would need the ND filter for the long exposure. The strength of the filter you would need would depend on a few things.

First - the shutter speed of the 'normal' picture with all motion stopped. Then you need to figure out how long of an exposure you need to get the motion of the waves you want. Then figure out how many stops longer than the original exposure that is.

That's the filter you need.


To do it by changing the ISO, you would (I would, anyway) do it the other way around. Start with the long exposure - this will be the ISO 100 shot. Now figure out how many stops shorter shutter speed you need to stop motion, and that's how many stops you have to raise the ISO.

Depending on how sunny it is, you will have to stop down quite a bit with no ND filters... (It might not be possible - you might have to wait for dusk/dawn.)