Ilford vs Kodak exposure indexes

[wskmosaic]

I know that everybody's EI experience is unique. Nonetheless, I'm looking for whatever experience there is out there.


I'm coming back to 4X5 photography after a couple of years and find that my standby--Kodak Plus X has gone the way of the dinosaur. So I'm switching to Ilford's FP-4. How close am I likely to come to truth--same lens, same camera, same developer, if I simply use the exposure index I found for Plus-X and use it with the FP-4, without retesting?

Incidentally, I have exactly the same question for a switch from Tri-X to HP-5. Would the results be close enough without retesting?

And I notice that the digitaltruth.com data base doesn't test any asa for HP5 below 200, while Tri-X gets results all the way down to 50. Is that because HP-5 is less flexible than Tri-X?
tnx
Warren

[ic-racer]

When I have tested HP5 to Tmax 400 the speed difference is small. Test was at one second with tmax developer for both (non ISO). In my darkroom, T-max 400 has a slight edge in speed but it was less than 1/3 of a stop. In general use I use the same EI for both HP5 and Tmax 400.

Realize that both films have their ISO speeds adjusted to 400 with trimmer dyes at the factory. The differences in my tests could be related to one of the following non-ISO conditions:
a) Tmax 400 more sensitive to the wavelength of my sensitometer light source
b) Better reciprocity at 1 second for Tmax 400
and/or
c) Slight speed gain with Tmax developer (not an ISO standard developer) that is shown only by Tmax and not HP5.

So, my reasoning is that if the ISO is similar than any exposure index would be similar, and again I use the same EI for both.

[mikew]

Honestly, I would do new testing - just as a policy; it's part of learning about a new film and its reactions to different developers. Having said that, I use HP4 a lot and it has a ton of latitude. I've seen it rated from ISO 64 to ISO 500 though I keep it around ISO 125. It's probably one of the most versatile, fine grained, and sharp films that I've ever used; and XTOL is one of the best and most recommended developers for it. That's where I would start.

Best of luck!

Mike W

[Drew Wiley]

I've always found Ilford's ASA ratings a bit too optimistic, and generally cut the speed in half when testing. It's all really related to where the toe and shoulder of the
film are going to fall, however, and how you want the extremes to look. The current
T-max films have a straighter line, further down into the curve, so will give shadow
detail close to rated speed, all else being equal (given a developer which works at
full speed).

[wskmosaic]

Honestly, I would do new testing - just as a policy; it's part of learning about a new film and its reactions to different developers. Having said that, I use HP4 a lot and it has a ton of latitude. I've seen it rated from ISO 64 to ISO 500 though I keep it around ISO 125. It's probably one of the most versatile, fine grained, and sharp films that I've ever used; and XTOL is one of the best and most recommended developers for it. That's where I would start.

Best of luck!

Mike W

Mike:
Did you mean HP-4? or FP-4 or HP-5?
Or am I missing something?
Warren

[Henry Ambrose]

Testing for yourself is always a good idea but a place to start can be helpful. BTW, both films are very easy to use.

Since you are starting over I assume you will be buying new developer and film, so I have a suggestion. Buy some Xtol, mix per directions with distilled water and for your working solution dilute it 1:3. Rate your FP4 at 100 and the HP5 at 320. Develop 13 minutes for FP4 and 16 minutes for HP5 with gentle agitation every minute. If you're using trays use continuous slow shuffling or for single sheets lift, drain and replace every 15-30 seconds. You're gonna be real, real close.

[mikew]

Warren,

I was only referring to Ilford FP4 - awesome film! - in my previous post.

As far as HP5 goes, it doesn't respond as well to push processing as Tri-X. The limit of HP5 is about one stop.

Sorry if I've misunderstood your post. I'm not sure if you're looking to find out the "true" speed of the film or just push/pull processing information. Either way, I would do tests: things like finding the desired Zone I density (net) of .10 to determine the film's threshold.


Mike W

[ROL]

I'm not much of a fan of film testing either, although sometimes it is necessary to get what you want. I presently use all the films mentioned (assuming Tri-X is TXP 320) in 5X7. Not having a clue as to your developer of choice, I have posted my personal findings here (http://www.rangeoflightphotography.com/news/film). Hope this helps.

[Sal Santamaura]

Warren,

I was only referring to Ilford HP4 - awesome film! - in my previous post...I suspect you were referring to Ilford FP4 Plus, right?

[mikew]

LOL...sorry, big typo! Yes, FP4...I hope they don't make an HP4. Sorry

[Mark Sampson]

Ilford replaced HP4 with HP5 in the mid-70's.

[wskmosaic]

Much good to chew on here. Many thanks
Warren