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GAF ST/1000 and 500ASA


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#1 Art Leal

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Posted 03 August 2008 - 01:11 PM

I have a GAF ST/1000 from 1971. The unit works well and films come off surprisingly sharp. It has a feature that was geared for the 500 ASA GAF Black & White Super 8 film which was made at the time.

The camera has a switch on its right side which when activated is supposed to properly expose the 500 ASA film, but only if the cartridge is speed notched for 250 (or as GAF calls it: the "speed feeler".

This camera's exposure ratings are 25-250T/16-160D

I immediately thought of what this would mean for the 500T Negative. Anyone care to speculate? Do the negatives work well when "properly" exposed, and not overexposed as Kodak recommends? I can't say since I've never had a cam that reads 500.

Does this not apply since it's a color stock and not B&W?

I will test a roll today. My testing will include a bright sunny day (which today is), and some indoor shots (If I were to guess on the indoors I'd say I'd need adequate lighting).

I have included two images from the camera's service manual.

Thanks

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#2 Art Leal

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Posted 03 August 2008 - 02:28 PM

Thought I'd add this piece of info as well regarding the B&W GAF film from Martin Baumgarten's site

GAFBW500 (rated ASA 400 Daylight)
(rated ASA 400 Tungsten w/o filter [cartridge removes filter]) Note: This also applies to Anscochrome 500 Color Daylight High Speed Film

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#3 Jim Carlile

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Posted 03 August 2008 - 09:42 PM

Hi Art,

Yeah, Martin's the real expert on those GAF cameras, which are really good ones, too. I think yours is a Chinon.

I'll try to explain without getting too complicated.

GAF 500 was rated at ASA 500, but there is no ASA 500 speed-notch indice in the super 8 standard. So, what cameras would do (if they could) is they would read the film at ASA 640-- I suspect this film was speed-notched at this highest super 8 ASA-- Martin would know-- I think it was....

Then-- because the film was supplied in a filter 'notchless' cartridge, the filter pin would be pressed in, thus setting the exposure meter to the low ASA of the speed-notch size, which for ASA 640 is ASA 400 (2/3 of an f/stop lower.)

That's another part of the super 8 notching protocol-- notchless cartridges are 'daylight' cartridges and hence set the camera to the 'daylight' ASA of the speed-notch, which is always 2/3 stop lower than the tungsten ASA.

But, ASA 400 is not ASA 500. So, all other super 8 cameras will automatically overexpose the ASA 500 film a little. There's no other way to attain a true ASA 500 setting. Except on your camera.

From the manual, these GAF cameras are set up to read a high of ASA 250 tungsten, which makes sense, because that was about the limit in those days anyway-- few films were ever rated above 200, but for the GAF 500. But, this camera has a toggle switch which-- like it says-- throws out a resistor to exactly double the ASA setting, which would be the proper ASA 500, not 400 like everybody else.

That's a cool feature which I've never heard of. That instruction book is great, too, except the ASA sliding part is over-complicated, because all it's pointing out is that each ASA notch size goes down the same amount.

For modern V500T, you can use this camera and its special ASA 500 method, but with some adaptation to the cartridge. Kodak speed-notches this film at ASA 400T, then supplies it in a daylight notchless cartridge to kick it down to ASA 250-- the daylight complement of the 400T/250D speed notch size. That's the way they like it.

So, all you have to do is cut a filter notch in the camera, and then slide the toggle switch to the special ASA 500 setting. What will happen is your camera will read the ASA 400 speed-notch size as ASA 250 (the highest it will go,) and then the toggled ASA 500 switch will double it to the proper setting. If you don't cut a filter notch in V500, I suspect it will read your film at ASA 160-- the low daylight ASA of the ASA 250T speed-notch size, the highest the camera will read.

Now, whether V500 looks as good at ASA 500 compared to overexposed at ASA 250, I'm not sure.

Remember too, that when you use daylight notchless cartridges, your camera has to be able to read the 'daylight' settings-- i.e., it has to be SMPTE compliant.

Most older ones are, but not all. I suspect yours is, but it wouldn't matter anyway if you have a filter notch in the cartridge, because its only utilized with daylight notchless cartridges.

Edited by Jim Carlile, 03 August 2008 - 09:46 PM.

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#4 Rafael Rivera

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Posted 04 August 2008 - 01:46 AM

I've used Vision2 200T S8 and would say that it has at least 2 stops of under and over exposure. I normally overexpose negatives, it gives me more headroom during telecine.
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#5 Jim Carlile

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Posted 04 August 2008 - 05:58 PM

Right, overexposure is preferable for that negative film and that's why Kodak sets theirs up to go at least 1 stop over. Of course with manual exposure you can do anything you want.

There's a couple of typos above-- first is that you cut the filter notch in the cartridge, not the camera (!) The second is that for years Kodak made 4-X, which was a B/W film rated at ASA 400. I believe they notched it at ASA 640T and then used a notchless cartridge to kick it down to ASA 400, the 2/3 stop daylight complement of the 640T/400D speed indice.

I'll have to look at an old cartridge for sure, but no matter how they notched it, most cameras would overexpose 4-X because they didn't detect any speed indices above ASA 250T, if even that... On an old box I notice that Kodak recommended manual exposure for this film. The GAF camera is unique because it was set up to run GAF 500 straight-- pretty cool.
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#6 Art Leal

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Posted 04 August 2008 - 09:45 PM

Jim many thanks for the input!

One curveball...I noticed that whether or not the notch filter is cut, once the "GAF 500" switch is pushed in, the 85 filter goes out of position. I confirmed this by looking in the gate while running the camera.

So, if its set to "read" 500 ASA, I'm worried it will affect the pictures look for daylight shot, being the 85 filter is moved out of the way.

I took two rolls which I'm sending out to Spectra tomorrow. I took two shots of each scene, one with the 500 switch in place and the identical scene without. I will post as soon as I get them returned.
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#7 Jim Carlile

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Posted 04 August 2008 - 11:16 PM

Yeah, the reason for that is if the internal filter is in the way, it will cut down the effective ASA 2/3 of an f/stop, which would be about ASA 350, defeating the purpose of the GAF 500 B/W film in the first place, which doesn't need the 85 filter anyway.

So, they automatically kick it out of the way, which means for neg color film, you use an external 85. Not always necessary, though, and yes, its use will cut down the sensitivity by a 2/3 f/stop.

Kodak does the same thing by putting Tri-X in a notchless cartridge-- it keeps out the internal 85, thus preserving that 2/3 extra stop. They do the same thing with the new Plus-X, but for an additional reason: they speed notch the film at ASA 160, then use the notchless cartridge to kick it down to the correct ASA 100 (2/3 of a stop down.)

Edited by Jim Carlile, 04 August 2008 - 11:17 PM.

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#8 Art Leal

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Posted 04 September 2008 - 03:07 AM

Here are some samples obtained from shooting with this camera. Overall the outdoor footage was good with not too much grain. The indoor shots had more noticeable grain in the shadows and darker areas when the 500 ASA switch was set to "on". The difference was almost negligible for outdoors, except for a bit more overexposed.

Thanks for the help!


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#9 Jim Carlile

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Posted 04 September 2008 - 03:22 AM

Yeah, I think it looks better overexposed at ASA 250. Kodak's right it seems. Was the bar-b-que footage taken with the switch on or off--?
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#10 Art Leal

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Posted 04 September 2008 - 11:45 AM

Yeah, I think it looks better overexposed at ASA 250. Kodak's right it seems. Was the bar-b-que footage taken with the switch on or off--?


So it would seem that overexposed works better. With the "switch on" shots, the darks were nice but they had bigger speckles of bright grain that were greatly minimized when the switch was off (can't really see it on the Youtube version).

So my assumption would be that rating a negative at it's exact ASA seems to render it a bit dark. All along I've been told that overexposing negatives is the way to go, but not what what would happen if exposed at it's exact rating.

I did the night shots with the switch off, figured I would need all the light I could get.
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