85B filter idea

[Super8SLiCK]

While I stocked up on plenty of K40, I will eventually run out. In the meantime, I've been tossing up some ideas on how to make my 40/160 ASA cam use the new 64T without using manual exposure.

I was thinking about getting an 85B filter and cutting a length to fit along the film gate area (not a tiny piece cut to fit inside the image area, but covering the whole gate area except the claw so as not to affect film registration).

If I remember correctly, and 85B should reduce exposure 2/3 of a stop and this method should not make the TTL meter compensate since it's not over the lens.

Any opinions on the feasibility of this?

[downix]

Actually, that's precisely what I'm planning on doing... once I can find some 85B gel filter I can cut to size.

[monobath]

I think the 3x3 inch gels are about the smallest size sold these days.

From Adorama 85B gel but they are temporarily out of stock, and this is $24 or so.

This might be better -
Lee 85B Polyester filter only $10.75 from Adorama.

Polyester is more durable than gelatin, but the gelatin filters have slightly better optical characteristics.

You can get the same two above for about the same prices from B&H also.

[reflex]

I was thinking about getting an 85B filter and cutting a length to fit along the film gate area (not a tiny piece cut to fit inside the image area, but covering the whole gate area except the claw so as not to affect film registration)

I suspect that you'll run into problems with scratches and the filter coming loose if you mount it over the gate. There'd also be registration problems, since the film guides are very shallow.

A better bet would be to mount it on the back side of the gate (if there's clearance), or perhaps further back in the body.

[Roel]

Interesting idea. Could you 'just' fix it by the screwing the gate onto it? It would not be in contact with the film then and there would be no possibility of scratching the film.

However the film would be further away from the lens which perhaps could effect sharpnes?

Roel

[mattias]

how about replacing the open sector of the shutter disc with a gel? or laminating the shutter disc onto a circular gel? if you have a camera where it's "easy" to get to the shutter that is...

/matt

[ccortez]

why can't we just replace the existing 85 filter material in the in-camera filter slider thingy with 85b?

[monobath]

I think the idea was to keep the filter out of the light path leading up to the meter, and then just compensate the readings by 2/3 stop. The camera surgery sounds complicated to me. For any manual camera, just use an external 85B filter and a hand-held meter with your 2/3 stop compensation dialed in (via ASA adjustment, for example), set the aperture on the camera as indicated and shoot.

[timdrage]

Won't having a filter that close to the film surface possibly cause problems if it gets dust etc on it at all? IE the slightest mark on the filter getting kind of 'contact printed' onto the film, as it won't be far enough away to be out of focus? If that makes sense?

[mattias]

the idea is to set the camera to tungsten, add a filter that the camera doesn't know about and thus get correct exposure in daylight with an automatic camera.

/matt

[christoph]

Won't having a filter that close to the film surface possibly cause problems if it gets dust etc on it at all? IE the slightest mark on the filter getting kind of 'contact printed' onto the film, as it won't be far enough away to be out of focus?

jup it probably will..
it will also alter the backfocus slightly, but probably not enough to worry.
++ christoph ++

[christoph]

the idea is to set the camera to tungsten, add a filter that the camera doesn't know about and thus get correct exposure in daylight with an automatic camera.

jup, i think he meant that if you add it in front of the the exposure meter prism it wouldnt do any good since the AE will be TTL..
afaik most super8 cameras have their lightmeter split before the shutter though, so this should be an non-issue.
++ christoph ++

[reflex]

why can't we just replace the existing 85 filter material in the in-camera filter slider thingy with 85b?

That would work for cameras that can read 64/40 ASA. For those that can only read 40/25, adding the "secret" filter behind the light meter should result in the correct exposure (as Matt said, switch the cam to tungste so it thinks there's no filter installed).

[avortex]

why can't we just replace the existing 85 filter material in the in-camera filter slider thingy with 85b?

The fact is that if anybody starts offering this service, there will be some clients for sure. What about including the modification of the exposure metering for E64T too?

[Super8SLiCK]

I did take into consideration the issues of film registration (which should be no problem) and the bigger issue of scratches, dust and optical matters.

I mainly want to avoid any camera "surgery," so to speak, while allowing it to expose 64T without using the manual override.

The worst case scenario is the results are lackluster; in such a case I'll just use K40 in DS8 and D8 (in order of preference) as long as that supply remains while I search for a 64T capable cam.

The plus side is no more jittery carts if I use another format.