DIY HD camera question

[Michael Maier]

I have been reading all these DIY threads. It sounds very interesting. Specially given we already have a working model. Th DRAKE. But it seems most people are having trouble getting them to work. So what's the biggest problem when building your won camera? I don't think is a camera head, since there are many out there. Is it storage? Is it capture? The DRAKE team seem to have got it together though.

[Keith Wakeham]

From my understanding their are several problems, each one specific to the camera design.

Obin is using cameralink and it seems his problem is with software more than anything, Its taking way to much processing power to preview and capture.

Rob scott is also doing software too, i think cameralink.

Some problems are steming from quality of the sensors and the available cameras, like being forced into rolling shutter. That is why everyone seems to be waiting for the altasens based cameras.

Drake seems very similar to what obin is trying to build, but I think drake had an outside company develop a new camera head and I think the major change was it used an external analog to digital converter that was of a higher quality than the on chip one. I could be wrong.

[Renat Zarbailov]

Are you guys talking about using a digital still camera to capture HDTV images? If not, then I have had this idea for a long time now. Imagine putting the fastest still digital camera to works are the campuring device for HDTV picture? I think Nikon D70S can shoot at the rate of 3 frames per secong in resolution that will rival even Dalsa (http://www.dalsa.com) camera. Without such an expense. The only thing is that it is not 24 frames per second. What do you guys have to say on this matter?

Thanks

[Keith Wakeham]

I though of this idea, but the real problem is getting the images off the sensor fast enough. I've seen some dslr's shoot at 8 fps and I have heard of ones shooting even faster with really fast CF media and shooting in JPG mode, but only for burst speed for a couple of seconds because of an internal buffer.

The only way to get the required speed from a dslr is to bypass all the circuites and almost rip the sensor and control curcuits out of the camera and start from scratch.

What most people are doing in using cameras with a cameralink interface, which is an industrial imaging standard. So most people are using industrial style cameras that are being adapted to film use.

But even if somehow you could get one of these Dslr sensors to go direct to hard drive, there are technical limitations to the sensor that will prevent it from reading out the images fast enough.

You might have a 6mp camera but in order to read off images from the sensor at 24p you would need a pixel clock of 288 Mhz.(pixel clock is normally 2x data clock) And most sensors will likely overheat or short out or just plain fail to fuction unless they were specifically designed for that speed or that the pixel speed is reduced by using multiple outputs.

Most single output sensors struggle to do the 74.25 Mhz needed for 1080i compliance. S/n ratio increases a lot you increase the readout speed.

So even if you could get a 6mp camera to output at 24p you have a signal to noise ratio which would put your quality down around SD or worse.

And one thing about dalsa is they are using a FT ccd. So not only does it have a 100% fill factor, (unlike IT ccd or cmos which are around 30-60%), When it takes a picture it acts very close to film by instantly moving the entire frame to a storage area all at once and the active area is again like blank film and taking an image while the stored image is being read out to a hard drive or deck.

Thats my take on it, someone might be able to prove me wrong by having the tech documents on these sensors, but until you have those or were on the development team that invented the camera you don't have a chance of increasing framerate from a dslr.

[Renat Zarbailov]

So what's the most efficient approach to create a DIY HDTV camcorder without reinventing the wheel? All it takes is a fast throughput between the sensor and the hard drive. What if the hard drive was replaced by solid state memory, not CF, but technology way faster. In other words this solid state disk is like a spounge and data is like water. I have been shooting HDTV quality 1 frame per second art films for some time now. I like the outcome for art reasons. Would like to have 24P capability though in a small package. The closest comes to mind is Kinetta, but not quite affordable.

Is there practical implementations of DIY HDTV cameras and where can they be seen, web site perhaps?

Thanks a bunch


Cheers

[Michael Maier]

I'm trying to understand how does DIY HD cameras work. So basically you buy aindustrial camera head? Does it take other lenses? What lens mounts are they? Do they do real 24p? How about other frame rates?
The you get this camera and records it to a HDD? You use USB? How do you record it to the HDD? Is there a computer involved?

[Rob Lohman]

Michael: currently those camera systems are COMPLETE computers.

1. industrial camera head indeed

2. usually they have standard industrial lens mounts, but in theory you could mount anything if you can get/make a mount. There are also convertors to mount one lens type to another mount system etc.

3. 24p is no problem, in theory such systems could go as slow or fast as the chips (CMOS) allow them to go

4. these camera's record directly to harddisks indeed through normal connections like (P)ATA and S-ATA, no USB2/firewire as far as I know (may get into speed problems as well)

[Michael Maier]

Thanks Rob. But how do they record straight to the HDD? How one connects the camera to the HDD? Wouldn't you need a capturing software to write it to HDD?

You say the cameras are complete computers, you mean cameras like the Drake are just a PC in form of camera with a lens on it?

[Rob Lohman]

I mean all current systems have a complete computer system inside the
"case" to work. I believe Obin still has a complete seperate computer (ie,
no case etc. yet). Since it is a computer that is running an operating
system like Windows or Linux/Unix writing to an attached harddisk is no
problem.

One of the difficult taks is writing the needed capture application, that is
what all the projects are doing or have already done.

[Michael Maier]

I understand you can't just use a normal NLE program to capture the files. So is anybody selling a capture software? What file type the cameras output actually?

[Rob Lohman]

Michael: it is far far more complicated than the answers I can give you to
those questions.

My post explained that the people building these things are making capture
programs, so indeed, you cannot use an NLE. Also, this capture is different.
The capture happens INSIDE (!!) the camera, not outside. What you do after
recording is TRANSFER the footage to your edit system by copying it off the
camera (or mounting the camera's harddisk to your computer, depending on
what someone has chosen to do with the camera system).

You most likely need special processing software on the edit system as well
before you can work with the data.

Filetypes are almost always special internal formats/files to maximize band-
width and lower resource needs etc. Since all but one camera is still in
development it is unknown at this point what the final output formats will
be.

The Drake camera system is basically finished and should be selling shortly
for (if I remember correctly) around $19.500. You cannot just buy a software
program and some camera head somewhere, at least not at this point in time.

You are buying a complete system.