• Please use real names.

    Greetings to all who have registered to OPF and those guests taking a look around. Please use real names. Registrations with fictitious names will not be processed. REAL NAMES ONLY will be processed

    Firstname Lastname

    Register

    We are a courteous and supportive community. No need to hide behind an alia. If you have a genuine need for privacy/secrecy then let me know!
  • Welcome to the new site. Here's a thread about the update where you can post your feedback, ask questions or spot those nasty bugs!

Synthetic aperture photography

S

Sam Hames

New member
Hi there,
Haven't had much time to really engage in any photography lately, but I have been noodling along on a side project that is looking at ways of extending what you can do with a handheld camera. If you take a series of photos in burst mode, you can register specific points in these images, then add the transformed images together. You end up with a controlled focal plane passing through the selected points where everything nearby is sharp, and everything further away becomes approximately defocused.

This synthetic aperture process can let you simulate a larger aperture, a longer exposure and also allows you to reduce noise or improve dynamic range. I've been working a little bit on some software that makes this possible, there's an example below synthesised from ~20 consecutive frames.



QueenStMallP1016041.jpg


​

I'm hoping to turn this into a usable tool for everyone to have a play with or find some use from. More to come later.

Sam
 
Doug Kerr

Doug Kerr

Well-known member
Hi, Sam,

Sam Hames said:
Hi there,
Haven't had much time to really engage in any photography lately, but I have been noodling along on a side project that is looking at ways of extending what you can do with a handheld camera. If you take a series of photos in burst mode, you can register specific points in these images, then add the transformed images together. You end up with a controlled focal plane passing through the selected points where everything nearby is sharp, and everything further away becomes approximately defocused.
Click to expand...

Quite fascinating. I look forward to hearing of your further work with this technique.

Best regards,

Doug
 
Asher Kelman

Asher Kelman

OPF Owner/Editor-in-Chief
Sam Hames said:
Hi there,
Haven't had much time to really engage in any photography lately, but I have been noodling along on a side project that is looking at ways of extending what you can do with a handheld camera. If you take a series of photos in burst mode, you can register specific points in these images, then add the transformed images together. You end up with a controlled focal plane passing through the selected points where everything nearby is sharp, and everything further away becomes approximately defocused.

This synthetic aperture process can let you simulate a larger aperture, a longer exposure and also allows you to reduce noise or improve dynamic range. I've been working a little bit on some software that makes this possible, there's an example below synthesised from ~20 consecutive frames.



QueenStMallP1016041.jpg



​

I'm hoping to turn this into a usable tool for everyone to have a play with or find some use from. More to come later.

Sam
Click to expand...


Sam,

i like the idea of looking at this as a way of investigating the effects of time. After all, you are using a butterfly net to catch transiences of a period of time.

I really want to learn more and would be fascinated to be able to experiment too.

Asher
 
S

Sam Hames

New member
I've finally had a bit more time to work on this, I thought you might like a peek at some of what is possible.

1. Noise reduction by combining 4 consecutive photos:

denoise_example.jpg

2. Controllable focus, after the fact. This set of images was made by averaging 30 or so photographs taken in a burst together. The top image is the sum of the images without registration, followed by registration with different focal planes at the front, back and then along the plane defined by the rocks for the final example. It works pretty well at web resolution, but not so much at the original file resolution.

focal_plane.jpg

3. Long exposure simulation, from 46 photos taken over 21 seconds.

long_exposure.jpg


I've hacked together a command line program to do this whole thing. It's called aperturesynth, and is available through the python programming language package manager PyPi. I wouldn't recommend trying it out just yet unless you're comfortable fiddling.

Next on my agenda is to build a GUI and package it up in a sane way (a long with a whole bunch of technical things I want to try out when I get the time...)
 
Tom dinning

Tom dinning

Registrant*
Hi Sam.
I'm a bit lost, as usual.
How does this differ from focus stacking or multiple image stacking.
I'm often stuck between what my head says and my camera tells me I can and can't do. Maybe I have the bull by the balls instead of the horns but if I want a shot with increased DoF and can't get it I can shoot a number of shots with differing focal planes and layer them in PS. I do this often when I want a landscape with a close foreground sharp. The exposure time doesn't really have any baring on the matter. I've done it in all sorts of lighting.
The other thing is the movement thing in the mall. Again, without too much effort, hand holding a camera, shoot off a few frames and then layer them in PS seems to do the job nicely.
It doesn't seem that complicated or am I missing something vital.
Cheers
Tom
 
S

Sam Hames

New member
Tom dinning said:
Hi Sam.
I'm a bit lost, as usual.
How does this differ from focus stacking or multiple image stacking.
I'm often stuck between what my head says and my camera tells me I can and can't do. Maybe I have the bull by the balls instead of the horns but if I want a shot with increased DoF and can't get it I can shoot a number of shots with differing focal planes and layer them in PS. I do this often when I want a landscape with a close foreground sharp. The exposure time doesn't really have any baring on the matter. I've done it in all sorts of lighting.
The other thing is the movement thing in the mall. Again, without too much effort, hand holding a camera, shoot off a few frames and then layer them in PS seems to do the job nicely.
It doesn't seem that complicated or am I missing something vital.
Cheers
Tom
Click to expand...

You aren't missing much - it is another kind of stacking. And it isn't that complicated, which is why it's a little mystifying why there isn't something available to do this already. (There is a mobile app that I'm aware of, that only works on video resolution and doesn't let you do the processing after the fact https://sites.google.com/site/marclevoy/)

The fundamental difference is that instead of trying to align the whole image, you align a small number of selected patches within the image. This gives you control over what is and isn't in focus, rather than attempting to align the whole image "on average" and accepting what you get out. The goal isn't increased depth of field but the opposite, a narrower, controllable depth of field.

It's certainly possible to do some of this in photoshop, especially with small camera movement like for the noise reduction example, but you're stuck with whatever comes out of the autoalign tool, or doing it manually, and neither of those will let you deal with very large numbers of frames.

Currently this only a proof of concept, I'm hoping to add features to make the whole process a little more useful.
 
Tom dinning

Tom dinning

Registrant*
Sam Hames said:
You aren't missing much - it is another kind of stacking. And it isn't that complicated, which is why it's a little mystifying why there isn't something available to do this already. (There is a mobile app that I'm aware of, that only works on video resolution and doesn't let you do the processing after the fact https://sites.google.com/site/marclevoy/)

The fundamental difference is that instead of trying to align the whole image, you align a small number of selected patches within the image. This gives you control over what is and isn't in focus, rather than attempting to align the whole image "on average" and accepting what you get out. The goal isn't increased depth of field but the opposite, a narrower, controllable depth of field.

It's certainly possible to do some of this in photoshop, especially with small camera movement like for the noise reduction example, but you're stuck with whatever comes out of the autoalign tool, or doing it manually, and neither of those will let you deal with very large numbers of frames.

Currently this only a proof of concept, I'm hoping to add features to make the whole process a little more useful.
Click to expand...

Now I get the difference. There are many times when I don't auto align, just shift the frame of one over the other until I have what I want. I can see how it can be used to alter the DOF or focal planes. Nice touch. Your engineering brain probably helps, Sam. I just fiddle until I get what I want and don't think it might be of any use to anyone else or worth organizing into something concrete and repeatable. Nor do I have the capacity to do it. Good to see there's some young blood out there who can come up with this stuff.
Here's
Tom
 
You must log in or register to reply here.
Top