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  #11  
Old 27th November 2019, 12:28 PM
Anon01 Anon01 is offline
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Quote:
Originally Posted by Brock View Post
If you type “reciprocity timer” in the App Store’s search function it’ll bring up an app that does the calculation for you according to film type. If you look for “Lee filters” in the App Store it’ll show you a calculator that works out the exposure for the big stopper.

I haven’t used either so can’t recommend them but they look handy.

Hope that’s of some help.


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I know the LEE one I use it all the time, I was asking HOW I calculate the exposure time using film with a big stopper
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  #12  
Old 27th November 2019, 12:33 PM
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Quote:
Originally Posted by Cannik View Post
OK, Can I ask a question please is it relevant to me.

I am used to shooting digital, with a lee big stopper which needs an extra factor of 10 for exposure, in other words

A shot of a normal 1/60th will be 15 seconds etc.

How will I calculate it then using Ilford FP4 or HP5 please remember I am NOT technical


??????? are these right to use

https://mkaz.com/film-reciprocity-tables/

https://apps.apple.com/gb/app/recipr...er/id459691262

https://play.google.com/store/apps/d...ocity&hl=en_GB

Thanks



.
I would approach it in two steps

First calculate the metered exposure without the filter - 1/60th in your example
Then adjust for the filter to give 15 seconds - this is in effect your metered exposure.

The reciprocity factor for the appropriate film needs to be applied to the 15 seconds in your example.

Hope this helps
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  #13  
Old 27th November 2019, 12:40 PM
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There's an Android App that allows for reciprocity failure with filters added.

Ian
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  #14  
Old 27th November 2019, 12:57 PM
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These are the factors you use for each film. You need a scientific calculator. There is one on an iPhone if you press the calculator button and turn the phone on it’s side.
You enter the number of seconds measured exposure, press the Xy (X with a small y top right) button, then key in the number from the chart above, followed by the = sign, and you get the corrected exposure.
It’s easier to do this than describe it in writing!
Alex


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  #15  
Old 27th November 2019, 01:13 PM
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Originally Posted by DaveInElland View Post
I would approach it in two steps

First calculate the metered exposure without the filter - 1/60th in your example
Then adjust for the filter to give 15 seconds - this is in effect your metered exposure.

The reciprocity factor for the appropriate film needs to be applied to the 15 seconds in your example.

Hope this helps
THANK you, now I need to work that out, all very complicated


.
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  #16  
Old 27th November 2019, 01:41 PM
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Originally Posted by Lostlabours View Post
There's an Android App that allows for reciprocity failure with filters added.

Ian

Should have added the App does bellows extension factor, filter density adjustment as well as reciprocity factor in all together.

Ian
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  #17  
Old 27th November 2019, 01:52 PM
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For FP4+ and 15 Secs...

Exposure = X↑Y = 15↑1.26 = 30 Secs
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  #18  
Old 27th November 2019, 01:53 PM
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The new formula does give shorter times than the previous one. I use a chart that Les Maclean posted in this forum years ago. I prefer the results it produces. Using the new formula for long exposure work with, for example, a x10 stop filter I had less shadow detail.
I’ve posted Les’s old chart, for box speed FP4, it is more in line with the older Ilford times. Together with a 10-15% reduction in development times it gives me good results. Always best to experiment and arrive at your own exposure times based on your working methods. Metering for long exposure work is subjective anyway and will always be dependant on the lighting conditions.
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  #19  
Old 27th November 2019, 03:10 PM
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Quote:
Originally Posted by Cannik View Post
THANK you, now I need to work that out, all very complicated


.
Which film are you using?
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