Home made camera designs?

[Steve Nordhauser]

OK,
I asked for information. The problem is that not much comes free. There is a threshold where the sensor costs are not the most significant system cost. PCs are getting cheaper but when you start pushing a bus and mass storage above about 60-80MB/sec, there is a cost step. It happens again at around 150MB/sec. Many of the things you want to leave behind - Bayer for 3 sensor, 30fps for 60+fps, 8 bit for 12 bit, large sensor area all increase cost. A 3 chip camera is really 3 semi-independent cameras with a $1-3K prism. 3x the data to store. That is why Bayer is so popular. If you use a good algorithm, the result is pretty nice. Kodak has some excellent algorithms under patent protection right now.

Low cost compression on-the-fly would really help. I will look into Cineform. Our SPIHT doesn't apply well here - very processing sensitive and not much of an improvement over JPEG2K for most applications.

For image lattitude, we have some with dual slope capability (resets overly bright areas part way through the integration) but the result is nice for security - doesn't really extend the dynamic range - it looks strange.

Large pixels cost more - silicon costs are mainly real estate and yield. Big chips are tough on both. Of course you are right - the coupling is better. When I use my Canon lenses on my c mount cameras, the FOV is much narrower due to the smaller sensor. Are there adapters with relay lenses?

Let's see where we can go at the cost/performance level that most people can reach before hitting 8Mpix.
Steve

[Obin Olson]

what you need is a ground glass system like I just made.. that way you can shoot with lowcost sensors that are small/cheap but use the 35mm lens system that gives you the look of film from the DOF 35mm priovides

[Steve Ipp]

Thank you, Les; a lot :)

[Laurence Maher]

Say,

Don't know, but figured this might come in handy to some of you guys

http://video-equipment.globalspec.co...ecurity_camera

maybe?

[Wayne Morellini]

<<<-- Originally posted by Steve Nordhauser : OK,
I asked for information. The problem is that not much comes free. There is a threshold where the sensor costs are not the most significant system cost. PCs are getting cheaper but when you start pushing a bus and mass storage above about 60-80MB/sec, there is a cost step.
--

I assume this is where a second/third HDD is added, the via boards do have some virtual raid features.

Maybe the answer is to prioritise the requests on cost and performance and then resolution. Of course the trade off for people is wherever to have 3 1/2 720p chips or one 35mm 1080 chip.
---
For image lattitude, we have some with dual slope capability (resets overly bright areas part way through the integration) but the result is nice for security - doesn't really extend the dynamic range - it looks strange.
---

Yes, your right, it has to be done progressively to look right (no big jumps).

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Are there adapters with relay lenses?
---

Yes there are relay, and condensor/feild lenses, possibly using special directional projection screens, much is being done in other threads recently, I made a bit of a summary of the little that I know over in the Viper thread.

---
Let's see where we can go at the cost/performance level that most people can reach before hitting 8Mpix.
Steve -->>>

Yes, my last post really breaks down to 3 levels 720 1080 and SHD, 1/2, 2/3, 35mm, each progressively more expensive. I have posted a lot of links in the viper thread. By the way what is the maximun average compression ratio for lossless?

About the 2/3rd inch sensors, I would settle for 1/2inch and use a 35mm/MF lense adaptor, but I included it because I think some people would prefer to use straight lense systems.

Thanks for the advice Steve, I had been curiouse about the price range of the splitter prism.

Laurence, really good find.

[Wayne Morellini]

http://www.dvinfo.net/conf/showthread.php?s=&postid=183804#post183804

<<<-- Originally posted by Valentin Wegerth : well at least a "2 plane imaging system" could be done easily and wouldn't be expensive. only thing you'd need besides 2 chips is the body of a slr camera. any slr cam has 2 image planes. if you take a picture the mirror that normally rests in a 45° angle is removed and thus the image (or focal) plane is at the very point the 35mm photo-film usually is transported. if the mirror rests in its 45° postition however the image is reflected to the viewfinder (2nd image plane).
i hope you get the point... now if you'd just remove half of the mirror, half of the picture would reach the 1st plane where our 1st cmos chip would be placed and the other half of the image would be sent in a 45° angle to the 2nd image plane - given the viewfinder removed . and could be captured there with our 2nd cmos chip. once again we use the merits of 35mm DOF (see my last posting). now if we put both images together there should be no noticable 'cut' or breach because either the image - actually the light - passing the lens is sent to the first cmos or reflected in a 45° angle to the second cmos.

any comments on my thoughts appreciated ;) -->>>

I said:

<<<-- Originally posted by Wayne Morellini : Good idea, you could simply keep going with this to get as many mirrors as you want. The edge of the mirror would have to be machined smooth and tappered to the front to reduce distortion (but will it cause diffraction?? patterns). It would have to be sealed air tight, it would be bad to clean.

This gives me an idea. If you had a half mirored surface (no backing) then half the light would be reflected to the veiwfinder and half to the film plane, going one step further the mirrors could be coated to only reflect an individual range of primary colour, using two mirrors, who needs a $1-3K 3 chip prism splitter? I'm going to bring this up in the Home made camera thread. -->>>

Now I have another idea, something like a lenticular array could be designed to split the individual direction the image primaries are projected to be read by three chips or three areas of one ;) A bit of single direction image compression would do the trick. This is based on an idea I have had a long time ago (as well as a projection idea): a lenticular array laid over a single sensor could take all the light per pixel area, mix it and split the primaries to 3 ajioning pixels (acting like little prisms). What you get is a completely acurate (less any abreviations) colour, each primary is sent 100% to it's own pixel (no major filter loses), all on a single chip, at very cheap price. The other advantages is that you get near 100% pixel area coverage, not 70% max, like in cmos, so you reduce the fly screen and bayer motion induced luma/chroma artifacts, and increase the used light (if you design it to miss the interpixel spacing. The other benefits of these screens is that they could be used as projection screens for the adaptors. I think I gave up on the idea after the foveon came out. So would this reduce the costs? When done right (with a couple of other adjustments) you could deliver all the transmittable light from a MF lesne right down to 1/2in chip. I have other ideas I am wanting to work on commercially aswell.

thanks

Wayne.

[Laurence Maher]

Say guys. How would a 1280 X 1024 chip do us as long as it ran 24p I guess we'd crop the image to a 720p image right? Got a possible lead on a camera that will do this.

[Les Dit]

I'm waiting to see what comes out in Bayer masked cameras. I'd like to see something that has 2048 across , and maybe has some data reduction on chip if that's possible. I don't like the complexity of 3 chip cameras, I think the Bayer cameras will eventually make the 3 chip guys fall into the video tube category.
I actually have three ccd cameras that are Bayer and are 3500 by 2300 pixels, but they are about 3 frames a second max. I'm converting two of them to mono ccd's for some new film scanning equipment for my company.
When can someone post a still Bayer pic from one of the current cameras, at 10 bits ? Even better, two images of the same scene so we can see the noise figure.
The CMOS cameras and sensors are cropping up like mushrooms lately, it's going to be interesting.
-Les

[Steve Nordhauser]

Laurence,
If it is a CMOS chip, it will probably have Region of Interest (ROI) capabilities built onto the chip. One of the advantages of CMOS is that the process is the same as IC manufacture which allows gates (registers, counters, comparators, A/D) to be put on the same chip as the sensor. This means that the window size and location (digital panning) can be dynamically changed.

In most parts, windowing in the Y direction will allow a faster frame rate. Some parts require the full line to be shifted, regardless of ROI.

This speedup can be used to your advantage, even if you want to go 24fps. I think it was Obin who suggested that to minimize the rolling shutter tilting artifacts, you want to readout as fast as possible. If you readout at 2x the required frame rate, you can toss every other frame. It still isn't global shutter, but it is cheap and available.

[Laurence Maher]

Interesting.

Yes, it is CMOS. Hmmmmmm

[Obin Olson]

larry, maybe you want to check out my thread called 10bit 4:4:4 I am building a CMOS 1280x1024 camera right now..

[Obin Olson]

Update:

got the K3 16mm camera today...hmm a well made unit I must say...not like a plastic toy... very heavy like a russian tank ;)
anyway i see a big issue ...if I remove the shutter then I remove the ability to see the image in the viewfinder....any ideas for this problem anyone?


when the shutter is open you see nothing in the viewfinder when it is closed it has a mirror on it that shows you the image in the viewfinder


I guess I could try and use a 2 way mirror but then how many f-stops would I throw out??

what mirror or beamsplitter should I look at if any?

http://www.thorlabs.com/SelectGuide2...d=beamsplitter

maybe the amount of light coming in with a beam splitter would be ok because 3ccd cams have beamsplitters right? so should I look at 50/50 splitters or?

[Les Dit]

Obin, I think you are really determined to use a real camera body for this, even though you will probably end up with using it as a metal box and nothing more ! Form follows function, and you are making function fit the form.... hehe.
Some of the best and highest quality photographs come from 8x10 cameras, and they are nothing more than a wood box with a lens screwed on the front. Thats all a camera is, really.
It's all good, as long as it works... go for it !

[Valeriu Campan]

...if I remove the shutter then I remove the ability to see the image in the viewfinder....any ideas for this problem anyone?

I guess I could try and use a 2 way mirror but then how many f-stops would I throw out??

Obin,
Have a look at 16mm Bolex cameras. They employ a beamsplitter (60/40). Maybe you can find somewhere one as a spare part...Their shutter is in the focal plane of the film gate.

[Valeriu Campan]

I would also second Les' point. Why do we have to look at a design based on film technology requirements?