Ilford Pan-F, exposure time compensation beyond 30 seconds...

[PKM-25]

Ilford's info gives reciprocity effect compensation through about 35 seconds for Pan-F, not beyond that though.

So for special effect reasons, I am looking to use this film up to a metered value of 2 minutes in daylight and would like to know the rest of the compensation scale beyond 30 seconds, mostly 45, 60, 90 and 120 seconds.

Also, for reasons of changing contrast I am also looking at rating the film at and developing for ISO 25, does this change the reciprocity curve at all, even in the documented findings?

I have good stock of other slow films like APX25 and Techpan for this kind of work but they are reserved for specific uses, especially TP. So I would like to get Pan-F dialed in a bit better for long exposure work since it is readily available.

To be crystal clear, I am avoiding slightly faster films like Acros and Tmax ( which I also use ) because they have good reciprocity beyond 15 seconds and that actually becomes problematic for this special task.

Any insights into further compensation times would appreciated...

 

[Tom Kershaw]

To be crystal clear, I am avoiding slightly faster films like Acros and Tmax ( which I also use ) because they have good reciprocity beyond 15 seconds and that actually becomes problematic for this special task.

Any insights into further compensation times would appreciated...

No particular advice for Pan F Plus, although I'm intrigued about good reciprocity characteristics being a problem.

Tom

 

[Thomas Bertilsson]

I've subscribed to this thread. Pan-F+ is a film I've started using a bit for long exposures, and while I'm going to do some of my own experimentation, with long exposures it's always nice to have some sort of starting point.

 

[pbo]

My first post since I have something useful to say

There's an iPhone app called Reciprocity Timer (the developer is "Pump Interactive" - have no connection with him), where you choose the film , exposure time, and some other parameters (+/-, filters, etc) and it gives you the final time to use. It's a paid app, but I've used it previously when shooting in the dusk/evening and it worked well.

 

[Thomas Bertilsson]

My first post since I have something useful to say

There's an iPhone app called Reciprocity Timer (the developer is "Pump Interactive" - have no connection with him), where you choose the film , exposure time, and some other parameters (+/-, filters, etc) and it gives you the final time to use. It's a paid app, but I've used it previously when shooting in the dusk/evening and it worked well.

Congrats on post #1.

Does the app have Pan-F+ data in it? What does it say for the times Dan was asking about above?

 

[pbo]

Congrats on post #1.

Does the app have Pan-F+ data in it? What does it say for the times Dan was asking about above?

It does have Pan-F+.

I don't think I'm entitled to release the content openly though - from the list of films in the app and the options available it's obvious the author spent time putting it all together, hence charging for the app. I sent you a PM.

 

[Xmas]

Try a PM to Simon Galley...

 

[PKM-25]

I PM'd Simon Galley last night, he is having a tech look into it. I also have the app mentioned above and one other one I have fed the Ilford data into. Apps aside, I was looking for a more scientific answer in addition to the apps. I am about to take off and go shoot a bit, I will likely use a couple rolls and see what I come up with too...

 

[Ken Nadvornick]

I'll be anxious to hear his response as well. I too have seen and used the reciprocity function graphs that stop at 35 seconds (uncorrected). But last summer found myself in a situation where my correction guesstimate (for FP4+) ended up being way beyond the chart at around 420 seconds (7 minutes).

I arrived at this correction via a WAG, and it worked OK, but a reliable extended conversion formula (or even just an extended chart) would have been so much less stressful...

Ken

 

[Dr Croubie]

While the app sounds great, something tells me that it was written from data, not from experimentation.
That is, whoever wrote the app just took numbers from the datasheets of all the different types of films, any times past those that came from the manufacturers are probably extrapolation or educated guesses.
Not saying that they're wrong, they could be very well educated guesses and accurate extrapolation, I just doubt that the app author tested dozens of films for dozens of times to see, that's a whole lotta work...

 

[paul_c5x4]

Came across this: Dead Link Removed which has some data for PanF+ - No idea how reliable the data is, but it should provide a starting point.

 

[Thomas Bertilsson]

While the app sounds great, something tells me that it was written from data, not from experimentation.
That is, whoever wrote the app just took numbers from the datasheets of all the different types of films, any times past those that came from the manufacturers are probably extrapolation or educated guesses.
Not saying that they're wrong, they could be very well educated guesses and accurate extrapolation, I just doubt that the app author tested dozens of films for dozens of times to see, that's a whole lotta work...

I like that it gives a starting point, however, and it appears that it's possible to insert personal times based on further experimentation. Not bad for two bucks.

 

[pgomena]

Came across this: Dead Link Removed which has some data for PanF+ - No idea how reliable the data is, but it should provide a starting point.

I've used this chart fairly successfully for FP4+ and PanF+, but I have to say, it's a bit fishy that most of the times listed for the Ilford products are the same. It can't be true.

 

[Ian Grant]

The problem with tables is they are to0 general. The type of light particularly time of day has a huge effect as the spectrum of the available light differs. So a 2 minute evening shot with litlle light from the blue end of the spectrum is quite different from a 2 minute exposure through an ND fliter (or well stopped down) in average daylight, and different still in brought sunlight.

When I did some practical testing with Fomapan 100 in typical low light levels I shoot in I found the Foma data way out, far less failure than they suggested.

So as Thomas says data can only get you to an approximate starting point, but with a little bracketing you can get a more accurate idea of how much you actual need to compensate for in different conditions.

Ian

 

[Andrew O'Neill]

I have always found manufacturer's data to be a bit excessive. I generated this data several years ago specifically for HP5+ and it has worked very well for me in the field. It also works well for other Ilford films. I have used it for Pan F, FP4+, and SFX. No development compensation required.

1sec give 1/6 stop more
2sec 1/3 stop
8sec 2/3
16sec 1 stop
32sec 1 1/3 (2.5x)
64sec 1 2/3 (3x)
128sec 2 1/3 (5x)
256sec 3 (8x)
512sec 4 (16x)

If you make up a curve with this data, you can find in between times.

 

[StoneNYC]

While the app sounds great, something tells me that it was written from data, not from experimentation.
That is, whoever wrote the app just took numbers from the datasheets of all the different types of films, any times past those that came from the manufacturers are probably extrapolation or educated guesses.
Not saying that they're wrong, they could be very well educated guesses and accurate extrapolation, I just doubt that the app author tested dozens of films for dozens of times to see, that's a whole lotta work...

I've been using the Reciprocity Timer app for over a year now, and I have to say that I've never ever been disappointed with an exposure, the guy who wrote the app is a large-format photographer himself, and is on the large-format photography forum. He's readily been open to adding additional times to certain films, including expired films, and yes he takes the data guide's and uses those times for most films, I've spoken to him about adding EFKE IR820 and he told me since there isn't any data, he will accept a special calculation I've found after I've tested it more thoroughly so that might be added soon, and you can also create your own film times so if you find the info wrong for your shooting style you can make a new one, in particular he lists the time and exposure data for the Kodak films with multiple options for those who have written specific data lines, I can't remember the names of the photographers, but they're very famous for using Kodak film and have their own calculations and he took those into account as well to add that as an option.

As for this film, I haven't personally tested it, but like I said, I've never ever been disappointed in any of the times that this app has given, it's very very accurate, and obviously the data is based on actual statistical data that the film companies have created, as long as you still shoot using your standard Exposure Index, everything else should essentially fall into line...

 

[Andrew O'Neill]

I've spoken to him about adding EFKE IR820 and he told me since there isn't any data,

Really? I think I posted my data somewhere...maybe over at the LFF... I also have data that I generated over the summer for Rollei IR.

 

[StoneNYC]

Really? I think I posted my data somewhere...maybe over at the LFF... I also have data that I generated over the summer for Rollei IR.

I found data from someone else but not actual data by EFKE themselves. He will only take data from the company or data based on testing with confirmation, doesn't want to get a bad rep for adding data by every random person. But EFKE is specialized so he said verifying the other times I found would be acceptable, but my bellows apparently isn't IR proof and my tests failed and I have to re-test, waiting for a good day and a back for my other camera to try.

 

[Andrew O'Neill]

Well, I've used my efke data for years and it's never let me down. Why doesn't "he" generate the data himself??

 

[StoneNYC]

Well, I've used my efke data for years and it's never let me down. Why doesn't "he" generate the data himself??

He doesn't have the film, it doesn't exhist in store, and he doesn't make very much off the app, in fact he hasn't even broken even for the time he's spent making it as I recall.

It would be stupid to invest time and energy in a film that isn't even made anymore. Lol.