Film Speed testing

[Paul Cocklin]

Alright, so it all started when my local camera store stopped carrying FP4+ for some reason. This was the film I shot in a multitude of formats (though I only ever bought 35mm and 120 from this store.)

So I picked up a few rolls of Delta100 in each size to do some testing. Here's the kicker though. My results show that my film speed for Delta 100 is ISO 160! Is that possible? I haven't shot anything with texture yet, so I don't know whether I'm going to like the film at all, but I'm intrigued. Next step is to shoot a scene and see how it handles real life.

I exposed a 35mm roll, doing the first 7 shots as ISO 100, 80, 64, 50, 125 and 160, placing each shot on Zone 1, along with an unexposed shot. I then did a series of zone V, zone VIII and film base exposures at each of the ISOs. Developed for 7 minutes which seems about right for the Zone VIII exposures. I'm waiting on a densitometer so I don't have any numbers yet, just eyeballing it. The best Zone I ISO was 160.

Now, this was developed in Pyrocat-HD 2:2:100, so I don't know what affect the stain is having on density, I guess I'll have to wait until I get a densitometer to figure that out. Would someone remind me again what a good densitometer would be? I seem to recall that I'll need one that can read separate color channels to correctly read a pyro neg.

Did I forget anything, or screw up anything? I triple checked the meter reading (Soligor Spot meter used) on each grouping of shots so I don't think that was an issue. I double checked my math on the exposures to make sure I was actually putting each shot on the zone I wanted. I can't think of anything else. Anyone think I definitely screwed up, or is ISO 160 a possibly correct ISO for my development routine.

I'll do some printing tomorrow to check for min-time/max black, and check the zone VIII printing at the same time.

Any comments welcome.

Paul

 

[nworth]

It's possible. The speed point (Zone I) is usually defined as the exposure that gives a density of 0.1 above base and fog. You don't say so, but my guess is that you are using and 18 percent gray card as Zone V for normal exposure. With many meters and films, it should really be Zone V-1/2 to VI (they are set to read average exposure as 12 percent reflectance). My experience with Pyrocat-HD is that it gives rated to somewhat less than rated film speed, so the meter problem may be showing up here. Developers do alter film speed by up to about +/- about a half stop or so, so your working film speed may be affected by the developer you use. Most films tolerate this variation well for most subjects. Try shooting some real subjects at 100 and 160 and see which negatives work best. If you can, include some "difficult" subjects.

 

[psvensson]

Delta 100 seems relatively fast. I just tested it against T-Max 100 and FP4+ in two different developers. I developed each film to the same contrast, checked with an improvised densitometer, and looked at the zone I density. Delta 100 was the only film I'd be comfortable exposing at box speed, or possibly EI 80 for some margin. FP4 gave about EI 64 and TMX EI 50.

These were both metol-based developers. In a high-sulfite developer with phenidone, you'd probably get more speed.

 

[ic-racer]

If you have a hand-held meter you can cover the meter opening with your test film. The frame that drops the reading by 1/3 of a stop (0.1logD) will be the one you want to use for you speed test. So, you can do this quick check before you get a densitometer.

Make sure you get a TRANSMISSION densitometer. I don't know of any that were "bad." The only "bad" one would be one that does not work or one that drifts. I would not expect a used unit to be calibrated so if it does not come with a calibration density patch you may need to buy a whole calibrated step tab from Stouffer or Kodak. If you see a 'white light' sensitometer, pick that up too

 

[Brandon D.]

I just recently tested Ilford Delta 100 in Kodak XTOL developer. And so far, I have concluded that EI 160 is the best film speed for my routine:

(there was a url link here which no longer exists)

In the scene I shot, EI 160 was the best tonal representation of what I actually remember seeing in the scene (e.g., in terms of image contrast, the house was well shaded, but parts of the roof and the grass had glaring highlights). And it's the type of tonality I want to see in my images in general. Not only that, the gray card that I placed in the scene (i.e., at the bottom-front of the door at that house), gives a spike in the very center of the histogram (in Photoshop) on the image rated at EI 160, which is cool with me.

I haven't worked with any other developers yet, but XTOL is traditionally known as a speed increasing developer.

 

[Anon Ymous]

Interesting Brandon, but how do you assess their quality? What are your negatives used for? Scanning or traditional printing?

 

[Peter De Smidt]

I wouldn't be worried about the result. Go shoot some images at that EI and print them. Does the negative have what you need to make a good print? If so, then you're fine. That said, for regular silver printing I'd recommend a zone I of .15 or more above film base plus fog. That'll give you better shadow separation.

There are lots of good densitometers out there, MacBeth, X-rite, Cosar... If you're using a staining developer, as you are, you want a color transmission densitometer, and you'll take your readings through the blue channel.

 

[Paul Cocklin]

Thanks all, for your words of wisdom. I feel better about the EI 160 rating and I'm on my way into the darkroom to see what my test negs will do on prints.

Peter, thanks a lot, I couldn't remember what color channel I was supposed to take readings through. I was looking at an X-rite, but they're crazy expensive when new. I'll find one eventually, though.

I appreciate everyone's help. Thanks again,

Paul

 

[psvensson]

As ic-racer points out, you can use a lightmeter. That's what I meant by "improvised densitometer." I use a Sekonic L308B with a homemade snoot, and measure the light coming through the neg on a light table. Difference in stops between two measurements x0.3 = difference in density

 

[Brandon D.]

Interesting Brandon, but how do you assess their quality? What are your negatives used for? Scanning or traditional printing?

For the most part, I followed Chris Johnson's Zone System testing procedure which is outlined in his book The Practical Zone System. His system is primarily based upon "visually" analyzing the test prints in order to find out which EI gives the best shadow detail at the highest film speed (according to personal, visual taste). And after that, the highlights are visually analyzed in order to determine the best developing time. The results are referenced with respect to pre-visualization notes (e.g., meter readings, and etc.).

My main goals were to map out and to meter Zones III - VII in my pre-visualization, to get the detail I wanted in those zones, and to get the style of contrast I like in the mid tones.

For now, I can only afford to scan, so my results aren't based upon traditional wet printing, i.e., I'm only digitally printing for now. Sorry to let you guys down.

But I definitely want to save up for a wet printing set-up (God willing ). I have shot digitally for the past few years, and I'm just now beginning to migrate into a film workflow. So, as a caveat, my results aren't based on traditional darkroom science (e.g., densitometer readings). But then again, every other [digital] area of benefit, or criteria, points me towards EI 160 when weighed against the other EIs. I hope this answers your questions.