Multi-exposure (composite) shots?

[acseven]

Hi,

I guess this is a tricky one, that probably can't be done from within CHDK, but here goes...

Some cameras (essentially DSLRs) are capable of taking multi-exposure shots. I am not talking about exposure bracketing or similar in order to make HDR photos, what I mean is to do something as such:

Splash on Flickr - Photo Sharing!
marathon on Flickr - Photo Sharing!


Cheers
acseven

[DataGhost]

I can control the shutter and the flash. Easily possible.. heck, I already did it (without flash though)
It'll be a while before it's properly implemented, though.. I only have some basic checking code and didn't integrate it with anything yet. I also need to make sure it doesn't do bad things. Maybe I can even time it with the flash.

Edit: I just kinda implemented it but I've got the feeling that I'm doing something wrong. I don't get anything near the effect on those pictures, I see a couple of transparent hands instead of solid ones. Actually quite logical, which makes me wonder how those other pictures were taken.
Thing I did was: take a 4-second exposure with flash, immediately close the shutter, wait 800ms, open the shutter, flash, close the shutter, wait 800ms, ... four times, while I was moving my hand in front of the camera. Looked like a ghost hand...

[acseven]

Nice!

So, if you have a 4-second exposure it will blur your hand, hence the blurred shot, isn't it?

If you try with a static object (i.e.  with 2 or 3 seconds in between frame shutter openings, in order for you to move the object), it should be better...

At daytime the long exposure shouldn't be a problem, and you should see your hand in two instances


Thanks for your tests

[DataGhost]

Well, it's transparent, not blurred. In the first shot my hand is exposed at position X and the background is exposed at position Y. When I move my hand from X to Y, the background at position X gets exposed and starts shining through my hand... same thing at position Y where the background is already on the sensor.

[A630Lover]

I think that the first picture was created with a software like photoshop or so. If you put your cam on a tripod, tke several pictures of your subject, and then just do the work on the computer, you should get the same result. I've already done it before with my old loyal Olympus C-4000 and a friend of mine ;-)

[DataGhost]

Indeed, that's what I thought. They don't really look like they're running, either.

[fe50]

Have you seen the pic here ?

Comment says:
I took four shots of this guy in the hope of catching a nice 'stance'. As it worked out I liked all of them and they seemed quite balanced so I decided to blend them into a single image.
I don't have a time machine so it was a little late for using a tripod, so I used this excellent HDR alignment tool Flickr: Discussing HDR Alignment Tool v2.0 in HDR

Then I dragged each of the four aligned pictures on top of each other using the 'darken' blend mode in CS2. "

[PhyrePhoX]

i think so too (regarding photoshop vs. camera, i think these were multiple exposures). DG, can you control the zoom while doing a long exposure? should be possible somehow.

edit: nice picture!

[DataGhost]

Yeah, why not? I already did that a long time ago as an experiment.

[acseven]

Hmm... So there's always a lot of photoshop involved!

btw, Photoshop CS3 has a Auto align feature that aligns layers. Works pretty good too. Now to make some of these shots... It's gonna take a bit of work!

Girls & Boys - Blur on Flickr - Photo Sharing!


Cheers

[cyril42e]

Very interesting...

Must be possible by automatically selecting pixels that are far from their average value (I mean, if you take 10 pictures, each pixel has an average value over these 10 pictures, and if in one image a pixel has a value which is far from its average value, then you keep it). To prevent noise you can also do it only if the connected component of such pixels is large enough (or just the largest is there is only one subject), and to prevent strange superimpositions only add independant connected components.

Does such software already exist?

[A570is]

Does such software already exist?
Yes, I think the "Tourieentferner" ( tourist remover) could do this http://philipptoelke.de/tourieentferner/index_en.html.
There is a special option for : "If you provide the command line option "-k" (keep), the program takes for each pixel the color, that is furthest away from the "majority-color"."

[cyril42e]

Cool, it looks exactly what I need!
Thanks A570is!