Backlight for Telecine- LED RGB?

[christoph]

Maybe this is daft of me, but do you mean 8 LEDs for a total of 3w? Or 8 LEDs @ 3W apiece? The former sounds low from my earlier camcorder experiments and the latter sounds rather high.

the rebels are around 3W a piece, so i meant 8x3W.
yes, this is rather on the high side, but if you want to keep them always on you probably dont want to run them on the max current. also, you might want to include more reds then green and blues to keep the shift low (frank uses twice the red as the others).

considering 3 is the minimum, and really too low for good diffusion, i'd say that 8 is probably a good start. franks latest unit has 24 LEDs.. which basically makes it a disco light ("turn up the music!" ;)

++ c.

[RCBasher]

franks latest unit has 24 LEDs.. which basically makes it a disco light ("turn up the music!" ;)

Yep...nice an bright! There is reason behind the apparent madness though...allows for heavy diffusion to create a softer light, better mixing and short exposure times ( usually <5ms) to help against machine vibration for example. I never did get a successful bounce system working, because of the light drop-off across the frame. Now I get heavily diffused and even back light

BTW, with such short exposures, there is no real need to remove the shutter blades...it's all done an dusted before the first alade after pulldown comes around.

Frank

[Roving6]

halogen with some CTB gels (or a 80A filter) is a surprisingly good option, since you can take advantage of the manufacturers color matching of the ccd bayer filter.
++ christoph

Perhaps this question will reveal me as a total optical ignoramus, but would you use the 80A filter on the backlight side or the camera lens side?

I would suppose that it would be best to have it out of the lens side optical path, so that would make me think it should go on the halogen light side. OTOH, 80A filters are usually installed on camera lenses....

I bought some opal diffusing glass as I'll need that regardless of which light source I settle on. At least I know what side of the film THAT goes on.

The Componon-S lens arrived today. Very nice.

Nathan

[christoph]

halogen with some CTB gels (or a 80A filter) is a surprisingly good option, since you can take advantage of the manufacturers color matching of the ccd bayer filter.

Perhaps this question will reveal me as a total optical ignoramus, but would you use the 80A filter on the backlight side or the camera lens side?

I would suppose that it would be best to have it out of the lens side optical path, so that would make me think it should go on the halogen light side. OTOH, 80A filters are usually installed on camera lenses....

not ignorant at all, i was asking myself the same question, and came to the same conclusion (although due to other reasons). then did some real world tests and found that it doesn't really matter.

personally i prefer it on the backlight because it allows me to use cheap gels (CTB) instead of an expensive filter.. and there is slightly less heat coming towards the film too.

++ c.

[Roving6]

Thanks, christoph. CTB gels on the backlight side it is.

Nathan

[RCBasher]

The Componon-S lens arrived today. Very nice.

Good find Nathan, hope you will be pleased with it. I should have mentioned before, use it at f4 for optimum performance. Down to f5.6 is usable, but performance drops off rapidly after that, as it also does when opened up more than f4.

The hard bit seems to be finding an adapter from C-mount to 42mm (or c-mount to any other size for that matter) which doesn't cost more than the lens! I made a quick scan around last night on behalf of someone else and saw prices around £40 to £50 8O
Other adapters, stepping rings, tubes, etc. seem reasonable....if not in c-mount!

I turned my c-mount to 42mm up in the lathe out of some Delrin...don't know if you have such a facility or know anyone locally who does that can help you?

Frank
EDIT: Oops! should have posted the above in your lens thread...oh well!

[Roving6]

Frank- I'll continue the OT lens discussion here as I started it as an aside in the backlight thread. I've already ordered all the various adapters I need. The 42mm to C mount adapter was the second most expensive bit, but I found a source for $30 USD. I don't know if the friend you're helping is in the UK and if shipping costs would be prohibitive, but here's where I found mine. (That IS what I need, right?) It's longer than the one you made, but I can always use a shorter extension tube combo to work around that.

Here's the adapter.

http://www.bhphotovideo.com/c/product/1 ... entax.html

My employer has a mini lathe and is fairly accomplished with it, but I'm trying to only ask for favors for parts I'm unable to find commercially or fabricate myself.

Nathan

[RCBasher]

Thanks for the link nathan...I'll pass it on. It's not someone I know well, but somebody who came across my website a while back and wrote to me for some advice. I heard from him again recently, asking about connecting up a Componon to c-mount! If it was for a close friend, I'd offer to make one up on the lathe, but it takes a while (mainly for setting up the gears for the thread cutting) and spare time is something I have little of at the moment!

Did you decide to stay with the MAC or build up a PC for capture? If the later, my capture program may be of use to you at some time and you will be welcome to try it. Main benefits are good quality debayer (courtesy of ActiveDcam), live histogram, dual monitor windows...the second one is able to provide a realtime corrected display for negative material without touching the capture to disk...and some other "nice to haves".

Good luck with your project!

Frank

[Roving6]

Frank,

I have decided to do the telecine project in phases. I'm collecting the optics and backlight supplies first, tidying up my projector drive mechanism, then I'll buy the camera and test it on my Mac. If everything proves satisfactory and I can scrape up the cash, I'll go for a dedicated telecine PC at that point. I'd love to try your software... is the user interface something a non computer expert can use?

Nathan

[RCBasher]

is the user interface something a non computer expert can use?

Absolutely...but I should let others whom are using it comment ;)

Frank

[RCBasher]

I should have mentioned before, use it at f4 for optimum performance. Down to f5.6 is usable, but performance drops off rapidly after that, as it also does when opened up more than f4.

Hmmm, at my age I should know better than to trust my memory! When reversed, the Componon performs slight better at f5.6 than f4.

Here are the comparisons:
f4:
http://www.cine2digits.co.uk/sch_f4_imi ... hq_rev.tif
f5.6:
http://www.cine2digits.co.uk/sch_f56_im ... hq_rev.tif

Sorry if I caused any confusion.

Frank

[Roving6]

Frank,
Did you happen to do any comparison tests of the aperture settings with the lens facing forwards? I'm going to be using a 1/3" CCD camera, and I think you said using the lens forwards was the best way to do it in that case. Of course I can experiment once I get my camera, but if you happen to know off hand...

The extension tubes, opal diffusing glass and 42mm>C mount adapter arrived. Just about time to take the plunge on the cam.

Nathan

[christoph]

s8 to 1/3" is a slight reduction (around 0.85:1), so it in theory it should work slightly better in normal position (optimized for about 0.1:1, if you reverse it for 10:1), but in reality since it's so close to 1:1 it won't really matter, so just mount it how it's most convenient to you.

as frank mentioned, most high-quality lenses will perform best around f5.6, and cheaper lenses around 8-11.

++ c.