Hp5 at ASA 141???

[neil poulsen]

I thought that I would do a sanity check; mine!

But before you render an opinion, let me explain . . .

I just completed a speed test for Ilford's HP5, and determined that the speed of my box of film is ASA 141, which is a half-stop better than ASA 100, and of course a half-stop worse than ASA 200.

Is this consistent with the results that others have obtained? Normally, I come up with ASA 200, so I guess it isn't so far off of typical. But, I thought that I would check.

I've accurately taken into account bellows expansion and actual shutter speed. My FB+F was 0.08, and my target was 0.18. I checked my densitometer with a Stouffer's standard that I keep on hand, and it's accuracy appears to be satisfactory.

[StoneNYC]

The actual speed of HP5+ is 400, ilfords speed is accurate, your tests must be off, or your qualifiers differ from ISO standards.

IF you're happy shooting it at such a speed, then do so... But that's way off the mark for me.

[Ken Lee]

This thread will likely grow to encompass the usual ping-pong game between those who use box speeds and those who don't.

That being said, you're still rather close to the usual results of those who don't use box speeds. If your prints are beautiful, then what's the worry ? After all, it's your water, thermometer, agitation, etc.

I presume your results are for N development. We know that effective film speed changes with expansion and contraction.

What developer by the way ?

[ROL]

I just completed a speed test for Ilford's HP5, and determined that the speed of my box of film is ASA 141, which is a half-stop better than ASA 100, and of course a half-stop worse than ASA 200.

The last time I tested, I was satisfied with 200. But, by all means keep testing – maybe you can get the accuracy to 141.4159, for a full measure of PI(e)!

[StoneNYC]

The last time I tested, I was satisfied with 200. But, by all means keep testing – maybe you can get the accuracy to 141.4159, for a full measure of PI(e)!

That would be EI 314.159 wouldn't it?

[ROL]

Touché.

[IanG]

Ken's right, many shoot HP5 at 200EI, tests involve equipment and other tolerances, like thermometers agitation etc.

I always shot HP5 at 200 but in Pyrocat I use box speed, I use practical tests rather than a Densitometer although I have acquired one this year after 45 years of photography.

Ian

[RichardRitter]

I have been using an ISO of 150 and it's producing great negatives. With great tonal range.

Read the fine print of the film manufacturer guild lines. It said subjected ratting.

Had a long talk with a film expert in the 80's from Polaroid. The listed film rating should be a starting point and then find what works for you. Different developers will give the film slightly different ISO ratings.

[neil poulsen]

Thanks for the input. 141.42135623730950488016887242097 it is, then.

[Heroique]

I just completed a speed test for Ilford's HP5...

Welcome to a tiny sub-set of forum members – the film speed testers.

Don't feel bad if no one agrees with your results.

Your glorious prints will win back their approval.