Fun with depth of field  

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AlexandreJ
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Fun with depth of field

by AlexandreJ » Fri Oct 17, 2008 1:05 pm

Ok, I just came back from a vision conference and would like to share with you the result of a talk there.
It was the presentation from this paper : flexible depth of field photography : http://www1.cs.columbia.edu/CAVE/projects/flexible_dof/

A quick resume. When you want a huge depth of field, each photographer knows it needs a really small aperture, the lower, the longest depth of field.
But the problem is then the time of exposure, it raises a lot. You can either have a short depth of field but a clean image or
a large depth of field but noise because of the exposure time.

Actually, there is some new solutions to that, not really new in fact : focus stacking : you shoot one image per focus plan.
Then, you use some software like CS4 or Z-combine. It works but you need to shoot several images and then merge them ( this merge notion is btw not so easy ... ).

Now, there is a new solution with a single image ! While shooting, you change rapidly the focus plan by rotating the focus while the sensor is capturing the scene. You'll get a fairly blurry scene, right, because in the same image you'll get all the focus plan plus many noise coming the same part but blurred. The good stuff ? This blur has a constant kernel, so it is really easy make a deconvolution of that in a single simple step. The result ? an image with the maximum depth of field with the lowest noise.

Imagine that : a new shooting mode in DLSR that will do a continuous focus change while shooting ( while the shutter is open, the drive that control focus make a
standard motion over the full depth of field ). Let's call that the continuous focus bracketing. Just by having this function, you'll get an extra large depth of field ( the one at min aperture ) with the noise at the max aperture, because everything has been shooted at the speed of F2.8 :)

So let's just vote for this new feature in coming firmware !

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by fma38 » Fri Oct 17, 2008 1:18 pm

I agree, this would be great!
Frédéric

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by Paul » Fri Oct 17, 2008 2:11 pm

I am sceptic, while the big Cam-Companies are not very impressed by wishlists.

e.g.:
It's an old wish to get more EV-Range on bracketing, not only +-1 with the Olympus DSLRs.
In terms of firmware should that be less than peanuts.

Customer-orientation in a mass-market, I wait a long time ...

Or is anybody around here with connections to those people, who can decide about peanuts?

cheers
Paul
Paul

close, but no cigar ... ... ...

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by GURL » Sat Oct 18, 2008 8:39 am

An open-firmware digital camera is something we need !
Georges

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by Phil Howard » Sat Oct 18, 2008 9:19 am

GURL wrote:An open-firmware digital camera is something we need !

I agree

But the camera companies would not like it because that means someone can create a feature and make it work in a lower priced camera. They might want to make such a feature work only in a higher priced camera to force people who want that feature to also pay for a bunch of other features they may not want or need.

I would like to add a feature in firmware that allows creating one or more "bracketing patterns". A bracketing pattern is a defined set of variations of different parameters to create exposures for. It would allow you to define how your bracketing is to take place, not just the degree of exposure change. You can, for example, choose to have the bracketing done as changes in aperture only. Or you can define some combination. Additionally, all other settings the camera is able to change are valid for bracketing, such as focus. The pattern would be a N-dimensional space (for N parameters) in which you can define the points to bracket in, and even the order (it would really be a list of N columns). Any degree of change would be allowed (not limited to 1 or 2 EV stops like most cameras today). You would be able to create multiple bracket patterns and give them names. A menu would allow you to choose the bracketing pattern to use by name.

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by fma38 » Sat Oct 18, 2008 4:29 pm

Intelligent bracketing should be much better. This can be done by analysing the first image, and taking the next ones so the entire exposure range fits into the sensor; GURL proposed this idea some time ago, and I would love to try it, but I can't even drive my Canon from Linux - no exposure modification is possible with gphoto2 library :(

I also agree that an open source firmeware would be great. But tthat also means an open-specification hardware, like the OpenMoko project did (cellphone), with the Freerunner device:

http://wiki.openmoko.org/wiki/Main_Page

If it has been possible with cellphones, it may happen with cameras...
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by BeeZed » Sat Oct 18, 2008 8:32 pm

The closest thing to open source firmware is CHDK. It is a community who have hacked the Canon firmware for non slrs. I have not used it, as I have a Nikon, but a friend uses it for 3d photography with great success. There are people working on Dslr, so in time...

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by Gordon » Sat Oct 18, 2008 9:22 pm

BeeZed wrote:The closest thing to open source firmware is CHDK. It is a community who have hacked the Canon firmware for non slrs. I have not used it, as I have a Nikon, but a friend uses it for 3d photography with great success. There are people working on Dslr, so in time...

Your right CHDK is a brilliant piece of software. It would be great to have it on DSLRs
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by hankkarl » Sat Oct 18, 2008 11:25 pm

AlexandreJ wrote:Imagine that : a new shooting mode in DLSR that will do a continuous focus change while shooting ( while the shutter is open, the drive that control focus make a
standard motion over the full depth of field ). Let's call that the continuous focus bracketing. Just by having this function, you'll get an extra large depth of field ( the one at min aperture ) with the noise at the max aperture, because everything has been shooted at the speed of F2.8 :)

So let's just vote for this new feature in coming firmware !

Well, f/5.6 may be better, my f/2.8 lens is way to soft at f/2.8. Or would the algorithm help that also?

I'd rather have the camera firmware do AEB so that the full dynamic range of the scene is captured, but the camera could do both dynamic range and focus stacking. After all, the 5D MII does 1080p video, so the camera doesn't even have to slap the mirror.

But how many images per position are reasonable? You do have to process each one.

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by mediavets » Sun Oct 19, 2008 12:06 am

GURL wrote:An open-firmware digital camera is something we need !

There was one once - tor something close to it - he Flashpoint Digita system that Kodal used in soem early diital camera - it was end user scriptable.

http://www.imaging-resource.com/PRODS/DC220/DC220Acgi.HTM

http://www.dpreview.com/news/0003/00030802flashpntpatents.asp

Didn't catch on.
Last edited by mediavets on Sun Oct 19, 2008 12:14 am, edited 1 time in total.
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by Phil Howard » Sun Oct 19, 2008 8:50 pm

hankkarl wrote:After all, the 5D MII does 1080p video, so the camera doesn't even have to slap the mirror.

When I put my 450D in Live View mode, the mirror stays up after the shot, except for really long exposures. I shot one pano set of 48 shots with the mirror up all the way.

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by hankkarl » Mon Oct 20, 2008 4:20 pm

Phil Howard wrote:
hankkarl wrote:After all, the 5D MII does 1080p video, so the camera doesn't even have to slap the mirror.

When I put my 450D in Live View mode, the mirror stays up after the shot, except for really long exposures. I shot one pano set of 48 shots with the mirror up all the way.

Does AEB keep the mirror up for all three shots? (ie does it open the mirror, take three AEB shots and then close the mirror?) You may have to use mirror lock-up.

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by GURL » Mon Oct 20, 2008 6:19 pm

Phil Howard wrote:
GURL wrote:An open-firmware digital camera is something we need !

But the camera companies would not like it because that means someone can create a feature and make it work in a lower priced camera. They might want to make such a feature work only in a higher priced camera to force people who want that feature to also pay for a bunch of other features they may not want or need.

I remember times where IBM mainframes were only usable thank to (or despite of) IBM bundled OS... http://en.wikipedia.org/wiki/History_of_IBM#Unbundling_of_software_and_services_in_1969.

A 2008 digital cameras is not 1968 mainframe but a sentence like "Many people believe that one pivotal event in the growth of the business software products market was IBM's decision, in 1969, to price its software and services separately from its hardware" suggest that separately sold camera "firmware" coud result in interesting improvements (this is quite evident for ergonomy, possible for image quality, etc.)

Phil Howard wrote:I would like to add a feature in firmware that allows creating one or more "bracketing patterns".

http://panocamera.com/blog/?p=26
http://www.hdrlabs.com/news/index.php?id=2122712049311920264

I would like to add features in firmware too. To allow shooting the next views with unchanged zoom setting (makes one of the LEDs blink if I move the zoom ring inadvertently), unchanged focus (even if move the focus ring), compute a series of bracketed values from two or more spot measures, switch off the antishake feature, mark the corresponding images with a tag to say they pertain to the same panorama and probably some more improvements I don't remember now...
Georges


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