Tag Archives: Fuji Acros 100

Reciprocity Failure

Up to now I’ve been shooting a lot of Fuji Acros 100 and the Freestyle “white label” version of the same (Legacy Pro 100). I haven’t really had to think very hard about the issue of reciprocity failure as a result.

Reciprocity failure is where the normal relationship of 1 stop of shutter speed being reciprocated by one stop of aperture in the opposite direction breaks down, and where an extra stop of exposure requires significantly more than double the exposure time. All films suffer it to some degree. Digital capture remains linear for any exposure time, but the trade-off is often increased noise.

With Acros/LP100 that doesn’t happen until you hit exposure times of over two minutes, and to date I’ve yet to run into a situation where I needed any longer an exposure aside from one shot where I was aiming to capture star trails (and in that case reciprocity isn’t really a problem, it might even be helpful in keeping the exposure of the overall scene in check). It’s an excellent emulsion for night shooting, in any case.

I’ve been trying out some Ilford HP5+ lately though and earlier tonight was out in downtown Roanoke, freezing my arse off with the intent of getting some night shots of city lights while Kelli went to her writers’ group. I needed to check on when the dreaded reciprocity failure kicks in first, however.

Now, Ilford provide pretty good datasheets for their films, right there on their website. But it struck me as a little odd that all of their films have the exact same reciprocity curve. Yes, they say HP5+ (a traditional type emulsion) has the exact same characteristics as the Delta films (their modern core shell type emulsions, similar to Acros and the Kodak T-Max range). Something smelled a little rotten to me.

So I dug around a bit more and found this article, “Black-and-White Reciprocity Departure Revisited” by Howard Bond, who decided to thoroughly test some film emulsions and compare their reciprocity characteristics to the manufacturers’ claims.

Turns out the Ilford datasheets aren’t too accurate. Neither are the ones from Kodak. Anyway, with both official and tested times taped to the back of my trusty Gossen Luna Pro F, I set out on an hour-long wander around downtown, shooting 12 big square frames in the Yashica-A. Mostly I kept exposure times in the sub-4-second region, where the official and unofficial exposure adjustments were nearly identical. For 8 second metered exposures I split the difference somewhere in the teens.

But in one case I did shoot two versions of the same scene, one adjusted according to the Ilford curve, and one adjusted according to Howard’s testing. I’ll be curious to see which worked best when I develop that roll.

Stand Development and Temperature Gradients

I’ve become quite keen on Fuji Acros 100 stand developed in Rodinal at 1+100 dilution for an hour, with a minute of gentle inversion agitations to start. It makes for negatives with just a little grain that I find pleasing and great retention of detail over a wide contrast range.

However, I did stumble into a problem with it the last time I developed some medium format film that way. My negatives had a gradient in the base+fog with one side being noticeably darker than the other, even with the naked eye on a light box. The effect was very pronounced in the scans. What happened?

Well, for the first time with stand development, I decided I should aim to keep the temperature around 68F (20C) to ensure consistency between rolls. So I carefully adjusted a water bath to temperature, let everything sit in it while I loaded the film onto the reel, then after the first minute of inversions I set the tank in the sink and waited for the timer to beep at me 59 minutes later. The water bath came up just over halfway on the tank; any higher and it would have caused the tank to float and fall over.

The room temperature was somewhere around 75F, so every so often I’d monitor the temperature of the water bath and drop an ice cube in to keep it where I wanted it to be.

Straight scan of negative, showing gradient in the film base. The base gets darker as you move to the right.

Straight scan of negative, showing gradient in the film base. The base gets darker as you move to the right.

So here’s what I think happened: as the tank sat there, the bottom 2/3 or so of the developer in it was below the waterline, the rest was above in air a good 7-8 degrees HOTTER than my carefully tempered water bath! Not only that, but the water bath also was untouched, and the thermometer bulb rested at the bottom of the bath so there could have been hotter water at the surface. As a result of this my developer must have had a temperature gradient of several degrees top to bottom. The hotter areas developed more base fog than the colder areas. When I ran through the motions of how the film would have been loaded on the reel, I realized the darker areas were nearest the top of the developing tank. In the scan there was maybe a half-stop of difference from one side of the negative to the other!

The good news? ACR’s gradient tool was able to adjust for this problem relatively easily, and the effect was uniform on the entire roll so fixed once, fixed for all the scans.

The bad news? Could be an interesting exercise in printing if I ever get access to a darkroom with enlarger. Slowly uncovering the paper from one side to the other to allow a little extra burning-in time in the most fogged area should be enough. Having never printed in the darkroom of course, I’m guessing here but it seems to make sense to me.

After inversion to a positive image, the "frame" area is lighter on the right, due to overdevelopment.

After inversion to a positive image, the “frame” area is lighter on the right, due to overdevelopment.

The moral? If I’m going to stand develop, best to just leave it at room temperature whatever that may be. It’s rarely going to stray too far from 68F. If I get a little more base fog, so be it; since my first act on starting to scan is locking Vuescan’s exposure setting to the film base anyway, I may not even see any difference in the raw scans. Nor should it pose any problem for darkroom printing if I ever get the chance to do that.