Reciprocity and Olympus OM-1n Film Camera

[LThatcher]

Hello everyone. I am new to the Photo Forum. I am just getting into film photography with an Olympus OM-1n camera (vintage 1970's). I have a 50mm and 35mm lens. I have developed one roll of film and see that I may have potential with this camera and the 35mm lens. I have been shooting digital for the last ten years and doing well; I understand photography, exposure triangle, etc. Now I am just looking for a challenge.

My question is, I want to do a long exposure in black and white with Ortho Plus 80 film. I have read that if you do over a 1-second exposure, you must account for reciprocity. The formula I found says Ta = Tm 1.25 (Ta = Adjusted time, and Tm = measured time). But math is not my best suit. I would be using a 10-stop ND filter, so compensation must also be made for this as well. I would probably shoot f/11, and the subject is a waterfall.

I searched the internet and youtube for help, but it was limited. I look forward to your conversation.

Best regards,
LuAnn

 

[RAZKY]

Hello everyone. I am new to the Photo Forum. I am just getting into film photography with an Olympus OM-1n camera (vintage 1970's). I have a 50mm and 35mm lens. I have developed one roll of film and see that I may have potential with this camera and the 35mm lens. I have been shooting digital for the last ten years and doing well; I understand photography, exposure triangle, etc. Now I am just looking for a challenge.
My question is, I want to do a long exposure in black and white with Ortho Plus 80 film. I have read that if you do over a 1-second exposure, you must account for reciprocity. The formula I found says Ta = Tm 1.25 (Ta = Adjusted time, and Tm = measured time). But math is not my best suit. I would be using a 10-stop ND filter, so compensation must also be made for this as well. I would probably shoot f/11, and the subject is a waterfall.
I searched the internet and youtube for help, but it was limited. I look forward to your conversation.
Best regards, LuAnn

Here's what Ilford has to say about it: https://www.ilfordphoto.com/amfile/file/download/file/1948/product/698/

Just so you know, reciprocity correction is a film issue - the camera means nothing.

 

[LThatcher]

Here's what Ilford has to say about it: https://www.ilfordphoto.com/amfile/file/download/file/1948/product/698/

Just so you know, reciprocity correction is a film issue - the camera means nothing.

Thanks, Razky, for the link. That is the website I found the formula that I noted in my original email. It is only part of the equation. I still have to account for the 10-stop ND filter and that is what I can’t figure out.

Thanks,
LuAnn

 

[Hardus Nameous]

Ilford is saying to take whatever your exposure time is and raise it to the 1.25 power.
So if I had an exposure time (measured by light meter) of four seconds I'd raise four to the 1.25 power and get an adjusted exposure time of 5.656 seconds.

I have no clue how much light is at this waterfall you want to shoot so knowing your aperature does me no good. However, since you're using a ten stop ND filter just add ten stops to whatever exposure time you meter (or guess by sunny 16 rule or whatever) then raise that value to the 1.25 power and that should be your adjusted exposure time.

At least that's my interpretation of what the spec. sheet says. I love Ortho 80 Plus but I don't think I've ever done any long exposures with it.

 

[RAZKY]

Thanks, Razky, for the link. That is the website I found the formula that I noted in my original email. It is only part of the equation. I still have to account for the 10-stop ND filter and that is what I can’t figure out.

Thanks,
LuAnn

Take your normal exposure reading, note the time, add the neutral density filter stops, and you have your metered time. Now consult the chart for the adjusted time.