View Full Version : 8x10 HP5+ Reciprocity Chart

Daniel Grenier
3-Mar-2004, 07:55
I have switched to 8x10 HP5+ and I have NO clue what the behaviour of this film is past the 1 second mark. So, I'd appreciate you letting me know what you have found to be proper reciprocity compensations with this particular film (exp.& dev. compensations that is). Any other concerns I should have with HP5?

Thanks for your recommendations.

tim atherton
3-Mar-2004, 08:20
have you checked the reciprocity graph from Ilford for HP5...?

Daniel Grenier
3-Mar-2004, 08:28
I did, Tim, but I do not typically trust manufacturer's recommendations on much - if anything. I'd rather rely on "real world" opinions such as those found in this group.

tim atherton
3-Mar-2004, 08:31
I've generally either gone by the chart or my other rule of thumb, which is guess.

steve simmons
3-Mar-2004, 08:36
Here are my adjustments

1=2, 2=4, 4=7, 8=19, 12=33, 16=50, 24=93, 32=145

steve simmons

these are seconds

David Karp
3-Mar-2004, 08:43
If Steve Simmons' numbers are the same as the ones in his book, I have found them to be accurate. From memory, they look pretty much the same to me.

Edward (Halifax,NS)
3-Mar-2004, 08:47
Steve, are you sure about 4=7? It doesn't fit the rest of the series. It is the only time that is less than double. Don't mind me. I spent too much time in math class.

steve simmons
3-Mar-2004, 09:20
I took these numbers from my book. I can't explain the seeming inconsistency. These numbers are the ones i use and they seem to work.

steve simmons

Sal Santamaura
3-Mar-2004, 09:27
In Photo Techniques' July/August '03 issue, Howard Bond provided results of some extensive long-exposure tests he conducted. I believe HP5+ was among the films he evaluated and, given the time frame, should have been the latest "improved" version of that emulsion.

Philippe Gauthier
3-Mar-2004, 09:30
The figures given reflect the graph in the Ilford data sheet; from about one stop to 1.5 stop up to twelve seconds; about two stops in the 12-25 seconds range; and 2.5 stops after 25-30 seconds.

David du Busc
3-Mar-2004, 10:14
I think Ilford says the factor is log 1.58 for both FP4 and HP5. I used this recently for some close up work and found it to be fine with FP4. A 2 minute metered exposure resulted in an adjusted exposure that left time to make a cup of coffee. There have been several threads on reciprocity failure. Try a search.

tim atherton
3-Mar-2004, 10:26
his is a previous email from Ilford on this:

If you wish to calculate a corrected exposure time based on the ILFORD chart, use the formula Ec=Em^1.48

Where Ec is the corrected exposure, and Em is the measured exposure, in seconds. Measured exposures of one second or less do not require any compensation.

Note that this formula is based on the chart. The chart was determined from experimentation. Times calculated past the chart should be good estimates, but are not based on ILFORD experiments.

David Carper ILFORD Technical Service

Andrew O'Neill
4-Mar-2004, 18:37
Here's my data from very careful testing and 6 years in the field:

1sec give 1/3 stop more (1.2x) 10 sec give 2/3 stop more (1.5x) 100 sec, 2 stops more (2x) 256 sec, 3 stops (8x) 512 sec, 4 stops (16x)

You can take this data and make a graph with it. Shutter speeds on the bottom of the graph starting at, say, 1/2 sec and plot all the way up to 512. Put stops on the vertical axis....1/3, 2/3, 1stop, 1 1/3, 1 2/3, etc. It'll give you intermediate times. No development compensation is required with this film.

Sal Santamaura
4-Mar-2004, 18:58
Since this thread popped to the top of the list, and I'm home at the moment where Photo Techniques back issues are stored, I checked Howard Bond's article. He questioned the validity of Ilford's single curve, since the corrections it indicates for both HP5+ and 100 Delta are very different from his results, which themselves differed for the two emulsions.

Here is a sample of Howard's HP5+ data; I suggest you see the article for his comprehensive results.

Meter indicated time/actual time required (seconds)