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Shooting BW 400 ISO film with 25A red filter.
Old 04-10-2016   #1
viewfinder-m2
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Shooting BW 400 ISO film with 25A red filter.

Hello All,
After many years of disregarding filters for shooting, I've decided to give it a try so this is my first time experimenting with filters. I'm awaiting a 25a red filter in the mail to shoot with BW films, mainly Tri-X and HP5. From what I understand, this filter has a +3 stop compensation. Question is: What do I set my camera ISO at if I'm shooting with 400 speed film? Is 3 plus stops 200 ISO? or 100 ISO from 400? Also I plan to use the filter for my Hexar AF and Contax T3. How would I program the settings on the camera to adjust for the red filter and 400 speed film? The EV comp feature is in 1/3 increments so I think it will not be sufficient for this. Do I manually adjust ISO? Or would it be best to "customize" the dx coding on the film canister to compensate for the 3 stops. Thanks in advance.

Mike
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Old 04-10-2016   #2
Swift1
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If your camera has TTL metering, set the ISO to actual film speed.
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Old 04-10-2016   #3
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When you set the camera speed manually, shoot Tri X or HP5 at EI 50, or actually, I would recommend to shoot somewhere between EI 25 and 32 ( for me, real speed of these films is EI 250), for shooting with cameras with auto exposure, a rule of thumb is to point the camera at a typical scene, set the ISO to the desired value ( e.g. 250) and take the light reading. Then apply the filter and repeat the reading again. You are likely to note, that the internal light meter will only differ by 1,5-2 stops. Then, you have to "downgrade" the ISO in camera by the difference.
Example: you set Tri X to ISO 250 on your Hexar, you take the reading. The reading is 1/250 f 8.0. Then you put the filter on and repeat the reading - it should say something like: 1/250 f 4.5. Then you need to downgrade the ISO in camera from 250 to about 80.

Do not follow Colton's advice, as it will lead to underexposure.
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Old 04-10-2016   #4
sevo
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Quote:
Originally Posted by Swift1 View Post
If your camera has TTL metering, set the ISO to actual film speed.
As a starting value - but depending on the colour responses of camera and film, that may still be off by a stop or two, to either side.
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Old 04-10-2016   #5
Moto-Uno
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I gotta say guys this is not very easy to understand . "In theory" a three stop filter rating
would reduce a 400 speed film to a 50 speed film. Bracketing either side of this should steer him toward the exposure he finds acceptable. And I'll add here that pictures from the above posters are typically excellent , so their suggestions come from experience .
Peter
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Old 04-10-2016   #6
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Thanks for the quick responses! So what I gather so far is to shoot 400 speed film at iso 50? Also when developing the film do I develop normally as if it were shot at box speed? Or develop according to the rated ISO (50)? This is actually more complicated than I thought!
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Old 04-10-2016   #7
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I'd develop it at box speed to start with. Time and familiarity should allow you to adjust it to your liking. There's many folk here that can make more experienced suggestions. Peter
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Old 04-10-2016   #8
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Quote:
Originally Posted by Swift1 View Post
If your camera has TTL metering, set the ISO to actual film speed.
Do this as a start. If you have TTL metering, then just set the ISO at 400, and develop at 400. The meter will take everything into account. If the meter is not TTL, then set the ISO to 50 to take into account the 3 stop loss of light, but develop normally. As with everything, this is a starting point. Don't overthink it, it's not that hard.

p.s. 3 stops takes 400 down to 50, halve it 3 times; 400->200->100->50.
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Old 04-10-2016   #9
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It sure would saved a lot of guessing if Mike would have supplied what model of camera he is using.

To learn more about filter factors, read this Wkipedia entry which has some charts.

https://en.wikipedia.org/wiki/Filter_factor

One can also get a Gossen Luna Pro F meter which has a built-in filter factor scale for instant adjustment (no brain strain). Other models of Luna Pros may also have this scale. Smaller meters lack this feature due to a deficit of space.

PF

ps: One could always print out the charts on the above page, cut them out and have them plastic coated to carry with them on their photo journeys.
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Old 04-10-2016   #10
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Looking up both the Hexar AF and Contax T3, neither have TTL metering, so you need to manually set the ISO to 50 (assuming 3 stop filter).
This will work on the Hexar AF, but not on the Contax T3
The T3 automatically sets ISO with DX coded cartridges and will default to ISO 100 with non coded cartridges. I'm pretty sure it won't allow manual override of ISO.
Can you even put a filter on the T3?
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Old 04-10-2016   #11
viewfinder-m2
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Thanks all: Moto-uno, Farlymack thanks as well for the link, and to save your guesswork, I've mentioned the cameras in my first post .


Quote:
Originally Posted by michaelwj View Post
Do this as a start. If you have TTL metering, then just set the ISO at 400, and develop at 400. The meter will take everything into account. If the meter is not TTL, then set the ISO to 50 to take into account the 3 stop loss of light, but develop normally. As with everything, this is a starting point. Don't overthink it, it's not that hard.
p.s. 3 stops takes 400 down to 50, halve it 3 times; 400->200->100->50.
Thanks Michael. Made it ALOT easier just now...
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Quote:
Originally Posted by Swift1 View Post
Looking up both the Hexar AF and Contax T3, neither have TTL metering, so you need to manually set the ISO to 50 (assuming 3 stop filter).
This will work on the Hexar AF, but not on the Contax T3
The T3 automatically sets ISO with DX coded cartridges and will default to ISO 100 with non coded cartridges. I'm pretty sure it won't allow manual override of ISO.
Can you even put a filter on the T3?
Thanks Colton that's what I was thinking. With bulk non-coded cartridges I can just set the EV comp to +1 which I believe will give me 50 ISO and Yes you can put a filter on the T3 with an adaptor made by Contax specifically for this purpose and for use of a hood IIRC.


M

Last edited by viewfinder-m2 : 04-10-2016 at 19:16. Reason: added more
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Old 04-10-2016   #12
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Quote:
Originally Posted by viewfinder-m2 View Post
Thanks Colton that's what I was thinking. Yes you can put a filter on the T3 with an adaptor made by Contax specifically for this purpose and for use of a hood IIRC.

M
In that case, you would need to set the exposure compensation to +3 for the red filter, but the T3 will only go to +2...
Reading the specs for the T3, I think the exposure compensation resets after every shot, so you would need to set it every time you take a shot.
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Old 04-10-2016   #13
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Quote:
Originally Posted by Swift1 View Post
In that case, you would need to set the exposure compensation to +3 for the red filter, but the T3 will only go to +2...
Reading the specs for the T3, I think the exposure compensation resets after every shot, so you would need to set it every time you take a shot.
Colton,
you can program the T3 to keep the same settings like flash and EV comp even when you power off the camera. Yes you are correct about the EV comp. maxing out at +/-2. I will either 'customize' a coded film canister to 50 ISO or when using bulk loaded film just tweak the EV which i can since it will default to ISO 100.

M
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Old 04-11-2016   #14
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Sounds like you're on to it.

Just remember that by changing the ISO when using the filter that you do two things;
1. Remember to change it back when you remove the filter, and
2. Develop for the 'unfiltered' ISO, in this case 400.
essentially you are 'tricking' the non-TTL meter.

But like I said above, you seem to be on to it.
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