Reciprocity Failure...

[njkphoto]

Hi to all,

I am about to develop film tomorrow and maybe this has been discussed so sorry. Well, I did some night photography last night using Ilford FP4 ISO 125 and Pan F Plus ISO 50. Exposures ranged from 8 sec to 30 sec..I did not add more time and I am wondering if I should develop the film more or you think I will get some good results as is.

Thanks in advance.
n.

[Mainecoonmaniac]

I don't think there's reprocity failure with these relatively short exposures. I wouldn't worry about it.

[njkphoto]

Thanks for your reply. I was looking into the tech specs of the film on the Ilford site and I think I read something that you have to compensate for even 5 sec which did not sound right to me.

[heespharm]

Fp4 and hp5 have the same reciprocity

[dasBlute]

In my experience, both of these exposures would require
alot of compensation with FP4 [I've never used panf for night work].
Additionally, at the higher exposure times, some underdevelopment
might be helpful, N-1 or more...

I use a chart developed by Gordon Hutchins, and this has worked on
many an occasion. His recommended exposures for fp4 are:

meter => suggested
2s => 3s
3s => 4s
4s => 6s
6s => 12s
8s => 18s
15s => 42s
30s => 100s
1m => 4m
2m => 10m
4m => 24m

[Bruce Watson]

I did not add more time and I am wondering if I should develop the film more or you think I will get some good results as is.

Reciprocity failure is about the lack of photons. If you don't supply enough photons, you don't form a latent image. If you don't form a latent image, you don't have anything to develop. Therefore changing development time is a moot point.

I think you'll find that no matter how you develop the film, you have empty shadow areas. This will be true because you didn't give enough exposure for the shadows.

Depending on the image and your intent for it, this might not matter.

If you want better reciprocity characteristics, consider using a more modern film, Acros, Delta, Tmax come to mind.

[Lee L]

image appropriated without permission


Fp4 and hp5 have the same reciprocity

The image you've posted is an iphone 'photo' of a .pdf of an openoffice spreadsheet that was posted by me here on APUG: http://www.apug.org/forums/attachmen...nchart.pdf.att

in this thread:
http://www.apug.org/forums/forum37/6...eet-films.html

Please do not post it to flickr as if it were a image created and copyrighted by you. It's not either of those things. Please reference the original here on APUG with a link to the .pdf, and don't reproduce it on your flickr account. I want it to stay with the original text and in its original context, with proper credit and attribution to Howard Bond for the experimental data on which the spreadsheet is based, and to Patrick Gainer, as the formula I used is the same as a method he published in PhotoTechniques with one small change. The internet is bad enough about taking things out of context and without attribution without us making proper sources even harder to track. Information of this kind without context and attribution becomes meaningless and useless noise.

BTW, my sources, among them Robert Reeves' Wide Field Astrophotography, test FP4+ and HP5+ as having differing rates of reciprocity failure.

Thanks,
Lee L

P.S. I see that you've also included several iphone images of pages from an Ansel Adams book on your flickr account next to the one of mine that you took. That's not fair use, and you should probably remove them as well before flickr gets complaints.

[mwdake]

My experience with FP4 says there is definitely a need for reciprocity adjustment for measured exposure times of > 1 second.
If you exposed a measured time of 30 seconds at 30 seconds I am not sure anything you with development will do any good.

Here is my notes, I use the same times for FP4 and HP5.

Measured New
1 2
2 4
3 6
4 9
5 12
10 32
15 57
20 01:26
25 01:59
30 02:30
60 06:50
120 18:40

The first column is measured time in seconds, the second column is the time to use in minutes:seconds.

You should try Fuji Acros sometime as it does not need any reciprocity for times up to about 120 seconds.

[njkphoto]

I wad just done a while ago developing the film. The results for the fp4 exposed between 15-30 sec were not bad at all. The Plus could use some additional exposure on some frames hut still good i think. I will post up some pics when i will scan and hit the darkkroom. I am thinking i will take a pic of the negative as well and post it.

I did get some Fuji Acros and try it soon.

[njkphoto]

In my experience, both of these exposures would require
alot of compensation with FP4 [I've never used panf for night work].
Additionally, at the higher exposure times, some underdevelopment
might be helpful, N-1 or more...

I use a chart developed by Gordon Hutchins, and this has worked on
many an occasion. His recommended exposures for fp4 are:

meter => suggested
2s => 3s
3s => 4s
4s => 6s
6s => 12s
8s => 18s
15s => 42s
30s => 100s
1m => 4m
2m => 10m
4m => 24m

I just shot a roll tonight, (freezing) and used the above combination of times using FP4. I use D-76 and it shoots for 11 min. developing time. Since I don't wan't to blow the highlights how much should I decrease development? I am thinking 9 minutes maybe?

Thanks