New HP5 Plus data sheet

[Oren Grad]

I see that Harman has posted a new version of the technical data sheet for HP5 Plus:

https://www.ilfordphoto.com/amfile/f...roduct_id/695/

On a quick first glance, other than a reformatting of the layout, the one change I see is new reciprocity correction data - they've backed off considerably from the numbers in the chart that they'd been using for years. See page 2 of the new data sheet.

BELATED EDIT: I want to acknowledge that Michael R was the first to report on the new Ilford reciprocity factors, in this thread:

http://www.largeformatphotography.in...sation-factors

Apologies for having forgotten about that!

[Steven Ruttenberg]

I was about to ask the question as I just purchased this to try it.

[Pere Casals]

There is a great difference for long exposures, near 1 stop for 30s measured !!

...but I've a doubt, for what zone the correction is ?


If the correction is for the speed point (-3 stops) it is one thing... but is it is for the Z-V meter point then it is a different thing, that correction will loss shadows.

What happens is that LIRF correction is very different for the different zones, shadows have a way higher correction than highlights.

[Corran]

What happens is that LIRF correction is very different for the different zones, shadows have a way higher correction than highlights.

This is standard for all films. High reciprocity correction requires changes to development time to reign in contrast. I factor this in for large corrections.

I have been using the new correction factors (time^correction) Ilford published with much success, shooting HP5+ ULF. HP5+ factor is 1.31. I use the Delta 100 factor for TMX too and it works out.

[Pere Casals]

This is standard for all films. High reciprocity correction requires changes to development time to reign in contrast. I factor this in for large corrections.

I have been using the new correction factors (time^correction) Ilford published with much success, shooting HP5+ ULF. HP5+ factor is 1.31. I use the Delta 100 factor for TMX too and it works out.

Bryan, ok, new graphs uses the 1.31 value, but I would like to know if after applying the correction what holds the same density (compared with no LIRF conditions) is Z-V or Z-II...

[Corran]

My guess is Zone V just like all the reciprocity corrections I've used do, at least according to my negatives. Why would it be Zone II correction?

Previous Ilford "generic" corrections always gave me heavily overexposed negatives so seems right to me.

[Pere Casals]

Why would it be Zone II correction?

Well, because ISO film speed is calculated in Z-II. ISO speed point is at 1/10 of the exposure recommended by meters, some 3 stops. If the correction was for Z-II then we would have equivalent shadow detail after the correction was made...

but I'm not sure ...

if the previous correction gave you overexposed negatives it would be intersting to know is at least shadow detail was well preserved, because then with a N- development overexposure would be addressed.

What I had been doing for night photography with HP5 was using that old correction to preserve shadows but doing an N-2 or 3...

[Corran]

Years ago when I was doing veeeeery long exposures (on TMX) I was doing N-3 or 4 development to reign in the highlights. But the shadows were correctly exposed. The overexposure I was having with Ilford products was throughout the range, not just upper mids / highlights blowing out. So this correction seems better at least in my usage.

You might've just been underexposing your night negatives (easy to do at night) and so the overexposure from reciprocity saved you. But who knows.

[Pere Casals]

I think that the way to control well night exposures is calibrating the film in LIRF conditions, this is making a contact copy of the stouffer wedge as usual but, instead using exposures of 1s, making 30s or 60s exposures, with light intensity acordingly lowered...

With that information we can predict the density what will result for any spot in the scene...

[Corran]

It seems to me that any reciprocity corrections given by Ilford (or others) really ought to be for Zone V, or in other words a middle value as metered by a TTL meter. Otherwise, they are pretty much useless without that caveat explicitly given. If one wants to delve into how much the shadows in the lower Zones will be underexposed even with the correction, one can calculate that themselves. One can be cognizant of the contrast changes easily enough without doing exhaustive tests. For forest scenes I often find the contrast lacking, so reciprocity helps me. For those high-contrast scenes such as interior derelict buildings with sunlight creeping in, a reduction in development is essential. Shooting some in the conditions one expects to be in gives a wealth of information - more-so than testing at home. IMO.