Continuing problems with tabular grain film

[richard_urmonas]

I had a previous question regarding problems with tabular grain

films which I thought due to development issues. I have now proven

to my satisfaction that it is NOT developing issues. (I used a

pro-lab to process half film and compared to mine).

 

So has anyone seen / know why I get low speed for tabular grain

film. My estimated speeds are: Kodak T-max 3200P = 320 ASA,

Ilford Delta 3200 = 300 ASA, Ilford Delta 400 = 125 ASA, Fuji

Neopan 1600 = 160 ASA. These films look exactly like they have

been underexposed, i.e. the curve shape is right, just shifted

down in speed. Conventional films are spot on for speed (FP4+,

400TX).

 

I have used several cameras and cross checked light metering. I

have even run some T-max 3200P using a black card (instead of grey)

so shutter speed + aperature matched those used for 400TX.

 

This is really bugging me as I used to get great results from

Delta 3200, then suddenly 3 months ago a complete lack of shadow

detail.

[lex_jenkins]

Lacking examples to demonstrate the problem and more specific information about how you've arrived at your conclusions anything we'd offer here would be guesswork.

[severi_salminen]

Lex is correct: give the information on the _whole_ process of determining the speed. Which camera, which meter, what settings on camera/meter, what kind of lighting, what kind of surface, how do you develop, how do you inspect the results etc. Describe everything.

 

Are you saying that using the _exact same_ (you meter identically, you develop identically etc.) procedures, you suddently get underexposed negatives with all cameras? Obviously that is not possible so we have to narrow the cause for this.

[andy_piper2]

It would bug me, too!

 

I just shot 400TX, Ilford HP5+ and Delta 400 in a test for practical film speed pushed 1 stop - and Delta 400 came out on TOP, with roughly 1/3rd-stop MORE density in the near-shadows (areas 3 stops darker than the overall scene) given the same exposure. (!?) Developer was Ilford DDX, if that's any help.

 

Meter setting was EI 1000 - but I can't claim that as the 'real' effective EI without a densitometer. Nice usable negatives, though.

 

(Query: is Neopan 1600 a T-grain film? I wasn't aware of such.)

[michael_fraser1]

"This is really bugging me as I used to get great results from Delta 3200, then suddenly 3 months ago a complete lack of shadow detail." OK. What, exactly, happened three months ago? That's really the question. Think back. Did you drop your meter? Is there a filter on your lens that you forgot about? (Don't laugh, it happens!) Did your city change the chemstry in your water supply? (You should be using distilled water for your developer anyway!) Is your thermometer/timer accurate? Assuming that Ilford didn't change the film, the problem is something that changed in your system three months ago. There really are no cosmic mysteries in photography these days.

[classcamera]

Just out of curiosity, what type of pictures are you taking with 3200 speed film?

[lex_jenkins]

Richard, here's one possibility that comes to mind...

 

I checked your photo.net page for sample photos and found none. However I followed the link to your personal website and noticed you're a fan of older cameras. Is it possible the shutter(s) on the camera(s) used for these tests is inaccurate?

 

For example, my Rollei 2.8C TLR shutter is generally accurate at faster speeds but goes one full second at the 1/2 second mark, and two full seconds at the 1 second mark. It's also labeled to the older standard, with speeds like 1/25, 1/100, etc., so there's always a bit of guesswork involved in transferring exposures between my meters and the camera. And if I'm recalling correctly this particular Rollei has continuously variable shutter speeds, at least up to 1/250. So whenever my TMX exposures are off my first assumption is that I didn't set the shutter quite right, not that there's something wrong with the film.

 

And even the best, newest SLRs with electronically timed shutters are seldom dead-accurate at the top speeds. It's also not uncommon for lenses to be off, especially wide open and fully stopped down. And who knows how accurate the f/stop tick marks are?

 

Anyway, the fact that your exposures with older style emulsions like FP4+ and TX are accurate doesn't surprise me. Those films, in particular, are very forgiving and will tolerate a lot of exposure error while still delivering technically "correct" if not aesthetically appealing results.

 

Just a thought.

[richard_urmonas]

OK the details of my testing:

 

The film was shot in one or more of: Minolta XD5, Minolta SR-T303,

Fujica ST605n, Rolleiflex 2.8D.

 

Metering by cross checking: Gossen Sixtomat digital, Gossen Lunasix 3, Weston Master II, in camera meters of above.

 

Densities measured on: Speedmaster TRC-60D universal densitometer, Fuji Densito V

 

I exposed the film using a grey card, in uniform cloudy conditions,

under the cover of a verandah. I checked for uniform light by

giving a "correct" exposure at start and end of test exposures, then confirming the density in both is the same. In one test

I used a black card so that shutter speeds and aperatures matched those used when exposing 400TX.

 

Speed was taken as the exposure which yielded 0.1 log density

above film base + fog.

 

This is not a development issue. I cross checked by sending half film to a specialist black&white pro-lab and compared the speed

with half developed by me. Both had identical speed.

[lex_jenkins]

Dunno, Richard, but the chances of all those films being so far below the nominal speeds? And so suddenly after you'd been getting good results? Very improbable.

 

Something else is wrong, probably either in your exposure or densitometry techniques. Sure, the true speed of most films is lower than the nominal ISO. But Delta 3200 suddenly being 300? Very unlikely.

[richard_urmonas]

Lex,

 

I only wish it was technique, but why then do FP4+ and 400TX

both give correct results ? Also I noticed this problem

when shadow details were lacking compared to similar shots done

previously.

[russell_brooks]

I dunno. Sometimes it's freaky. I got a .1 speed of Neopan 1600 at 160 once. Of the tabbed films the only one I like so far is New Delta 400. It actually is closer to a 500 speed film if developed in DDX. <br>But to your problem: in that case just use 400TX!

[evan_parker]

Well if it isn't developing issues, it isn't the camera, and it isn't your technique, what could it be (barring a sudden barrage of cosmic rays spoiling all your film at once)? It could be something easily overlooked, like leaving film in a car glove compartment for too long. You never know.

[severi_salminen]

"Speed was taken as the exposure which yielded 0.1 log density above film base + fog."

 

And I assume you mean Zone I exposure? 4 stops below "middle gray" reading?

 

Maybe you should do the tests once more because everything seems to be correct. Maybe your film batch was bad, or maybe you simply made an error in exposure? Or maybe the true speed (as measured per Zone I at 0.1 above fb+f) of those fast films are really something lower than 1000 - I guess not...

[michael_carboy1]

hi richard..

 

i think it might be useful to check into the ISO definition of the speed point.. if memory serves, the subject density curve has to have a crantrast index of 0.62 (slope).... then your 0.1+FBF will intersect the density curve at the point that corresponds to a log density of 2.4.. and every 0.1 variance around that corresponds to a third stop variation in speed.. for what it is worth, my analyses of TMZ and D3200 in DDX (1+9) suggest speeds of approx. 1200-1600 for the TMZ and 800-1000 for the D3200.

 

hope this helps rather than confuses

 

Michael

[severi_salminen]

Michael, I think (assume) that Richard was trying to measure the "other true speed" of the film: as done by Adams. He measured the speed which generates 0.1 above fb+f at Zone I, with normal development (development that gives 10 printable zones on grade 2 paper). ISO result will be different.

[richard_urmonas]

I am using a technique along the lines of Zone system tests. i.e. Zone I is 0.1 above FB+F. As Delta 3200 and FP4+ are the only ones of these

films I use regularly, the others have been developed to close to correct gamma, but without fine tuning. This should not affect the speed anyway. Most of these films have been tested more than once,

generally with different batches.