Exposure meter correct? (Carena Variogon Zoomex)

[atari82]

Hello,

i'm quite new to 8mm. I just got a (untested) Carena Variogon Zoomex camera from a friend. I replaced the broken PX1 battery with a new PX1A battery and now the exposure meter works again, but gives me unrealistic(?) values.

When i measure the wall next to me (dimmed room/evening sun) it says t=5.6 @ iso 100
My photo-camera says at 1/60th shutter -> f=2 (@iso 100)

When i aim the carena outside the meter goes till the end to t=16 (@iso 100)

What shutter-speeds do (automatic) film cameras have? Depends it on the frames/sec? iso 100 film ist quite normal, right?
I did read somewhere, that replacing the old mercury battery with a new one may mess up the exposure meter.

Thanks!

camera datasheet: http://super8wiki.com/index.php/Carena_ ... omex_Reg_8

[Lunar07]

You are using the PX1A at 1.5V. This is leading to the incorrect exposure. You should use a 1.3V battery for correct exposure.
On this camera you need the MR-50 adapter to regulare the voltage of a #357 1.5V silver oxide battery. Such adapters are the best and much better than using the Zinc Wein cell.
An example of the MR-50 adapter:
http://www.kanto-cs.co.jp/english/adapt ... er_en.html
scroll down the page.

[atari82]

Thanks, that was the right hint! Didn't realize that it had another voltage. Is there any possibility to compensate the exposure by setting to a lower iso? any experience? or not possible, because the meter is not linear to the voltage?

I'm going to holiday next week and would love to take the camera with me. I already ordered film but I think it's to late to order the MR50 as I can't find it anywhere in germany. Although i found the weincell 1,35v (same diameter?) here and people report to just fill it with some conductor.
Why wouldn't you recommend that? Is it inaccurate? because of the conductor resistance? as i can see the outer terminal is right next to the inner terminal. I probably wouldn't even need an conductor.

Thanks!

[atari82]

Ok, i found the answer in the depth of the net. 1.5V batteries lose voltage by getting older. The mercury Battery had always the same 1.35V output.
The zinc battery starts to die as soon as activated and doesn't last very long.

I have the possibility of manually setting the aperture. As i have an exposure meter it wouldn't be a problem. I would just need to know what shutter speed my camera has? Is it dependent to the film transport speed (e.g. 16 frames / sec.)?

[Lunar07]

I am not sure about the shutter speed. But shoot a test roll.
For the first third of the roll adjust ASA by 1 stop. For second third adjust it by 1.5 stops. For last third adjust by 2 stops. Of course adjust ASA for more exposure. Then compare and take it from there.
Be forewarned though, the PX1A you are using start delivering less current as you use it which may lead to erratic exposure. Mercury batteries as you know deliver constant current till the very end. An adapter like the MR-50 that uses a regular silver oxide battery has a voltage regulator in it that ensures constant current for life of battery.

[atari82]

I found another thread by you in 2007 which describes the battery problem: viewtopic.php?f=1&t=17249
(didn't find it earlier, because it says carena zoomex and i looked for Variogon)

You said, with an Alkaline Battery it would „underexpose by up to 1/2 of a stop“.

I guess it could be approximately an 180-degree shutter-opening, that gives you a shutter time of approx. 1/30 sec. @ 16 frames/sec.
Compared to my photo-camera this value you to low - should be around 1,5 to 2 stops.

Unfortunately i can't do a test-roll bevor my holiday or order the MR-50. I think i best go with the 1,35V zinc-cell and hope it'll last for 2 weeks.

By the way: here's a manual, that describes the „manual-aperture-mode“, but doesn't say anything about the shutter-opening-angle. http://home.scarlet.be/stef49/Collectio ... ex_II.html



Rotary shutter: http://en.wikipedia.org/wiki/Rotary_disc_shutter

[Lunar07]

I was writing a reply to your question while calculating the exposure when TWO of these batteries are used. In other words I answered your question with the Zoomex II in mind (Carena Zoomex II uses TWO batteries). My older post is correct. With ONE battery on the Zoomex, the exposure difference can be anywhere between 0.5 and 1 stops.

[cameratech]

From memory the shutter angle is a bit less than 180º, maybe 160º or so. Also there's some light lost to the reflex viewfinder. I think I calculated something like 1/45 sec at 16 fps and it turned out OK.