Film Speed vs Development

[ed_van_aalten]

I have always shot TRI X and Plus X. I understand that their actual ISO

respectively are more like 160 and 50 rather 400and 125. If I use these speed

and consider "Normal", do I compensate the development time or use the mfg.

recomended time? I use D76.

 

Thank you, Ed

[jmalever]

Ed,

 

I'm certainly no expert on these matters, but here is what I've been doing recently. I shoot TX at 200 and then reduce the normal (i.e. 400) times by 15-30 percent, depending on the conditions. If it is really flat outside, I'll increase the time a bit. I never did any film speed tests to arrive at these figures. I just read others' advice and experimented a little. It is working well for me. One of these days I'll get over my lazines and do the film speed tests so that I'm truly working with the optimal setup.

[leicaglow]

It depends a bit on the emulsion you're using. For example, the 4x5 sheet film, rated at 320, is often shot at 200. You should probably take a look at Ansel Adam's book, "The Negative", where he explains this a bit. I'm not sure he says it outright, but I believe it is done to provide more shadow detail. I personally do not adjust the development time.

[john_gleason1]

You could also try this source:

 

http://www.digitaltruth.com/devchart.html

 

Quite a few variations there.

[jay ott]

I think you should base your decision as to whether or not you need to compensate dev. time on the answer you get to the question, "at what point do you find your highlights blowing out?" and then work from there by cutting back on your time until you get them where you want them.

[howard b. schwartz]

i am no expert, however, i think the absolute best way to determine film speed/exposure/development is to perform the procedure as outlined in the adams' book, "the negative". this should allow you to determine your normal ("N") exposure and development times for your film, equipement, developer and technique.

[stwrtertbsratbs5]

I don't shoot the films you mentioned. But I do shoot Ilford HP5+, which is an ISO 400 film. I rate it at EI 200 and develop it for 14min in 1:3 D76 @ 68 deg with 2 inversions each minute (N). I arrived at this by running film tests. Perhaps you should grab a roll of HP5+ and see if you like the results.

 

For sheet film, I meter the shadows and vary development time to place the highlights where I want them. For roll film, I just use incident readings or adjust an overall reflective reading so that the average exposure is reasonable. Most negs should print nicely on a 2 1/2 filter.

[raczoliver]

Whatever film and developer you are using, it's really best to do a couple of test strips and see what works best for you. How much "real" speed you get from the film depends on your metering technique and even more. I am personally not a big fan of overly scientific tests involving densitometers and all those fancy things (maybe because I don't have a good enough understanding of them), but a couple of real world pictures exposed and developed differently can help you get in the ballpark.

[robert_grasing]

Tri-X and Plus-X are ISO400 and ISO125: that means that is their film speed when developed to certain standardized parameters, one of which is contrast.

 

However, many photographers find that the film contrast at the official ISO speed is too high: they prefer a softer negative, so they reduce developing time. Reducing developing time also lowers film speed. Hence, the common practice of cutting the ISO in half (400 to 200, 125 to 64) and reducing developing time about 20%.

 

If you have a condenser type enlarger, it is usually a good idea to use the above procedure: reduce developing time and cut film speed. If you have a diffusion type enlarger, you can use the official ISO film speed and developing times (but the above procedure will also work well with diffusion enlargers and in fact many prefer to use it).

 

The problem is, there are so many variables here to consider: the accuracy of your camera's shutter and your darkroom thermometer, your agitation procedure during developing, your choice of printing paper, your own taste and preferences, etc. So if your current procedures are giving you photographs you like, then I say stick with them.

[pete_andrews10]

The real ISO is what's printed on the box.

 

Kodak take a lot of care in measuring the speed of their films, as can be seen from the copious data supplied by the company. Tests I've done have confirmed to my own satisfaction that Kodak's published sensitometric curves are accurate and reliable. The B+F+ 0.1D speedpoint on Kodak's curves aligns extremely well with the reciprocal lux-seconds * 0.8 that gives the ISO speed - but ONLY for the recommended development time. Any other development time or temperature will give a different gamma from that laid down in the ISO standard.

 

In fact Kodak go beyond the call of the ISO standard, and publish a family of curves for most of their film/developer combinations. Those additional curves roughly correspond to N+1 and N-1 development in the zone system, although Kodak don't label them as such.

 

Kodak are not lying about their ISO ratings, because they can be verified independently and fairly easily. Of course, if you want to rate your film at a personal exposure index (EI) for any reason, then that's entirely your choice. But it won't be an ISO rating.

 

It'll help if you get your head round the fact that exposure and development are pretty much independent of each other. Exposure dictates the amount of shadow detail captured, or the placement of a key tone in the zone system, while development regulates the contrast of the negative, or the density of the most significant highlights. True film speed is hardly altered at all by the amount of development (within reason, since shortening development time too much will cut the effective film speed quite drastically).

 

If you follow the old maxim "Expose for the shadows, and develop for the highlights", then you won't go far wrong.

[bruce_watson1]

I think you are mixing ideas. The ISO is the ISO. It's the results of standardized testing.

 

When you do personal testing such as what you find advised by various Zone System texts, you find your personal exposure index (EI). This can be higher or lower than the ISO rating because it takes into account your personal equipment (camera, shutter, meter, darkroom, etc.) and processing (rotary, tank, or something else, developer, etc.).

 

Many Zone System people do their own EI testing and come up with a number that is lower than the ISO for a particular film. There are a number of reasons for this. But it all comes down to trying to keep the image data in the linear region of the film/developer/processing response curve. That is, it keeps the image shadow detail from being compressed into the toe of the response curve.

 

All of this can be easily reframed into just this phrase: Expose for the shadows and develop for the highlights. That's all that's really going on here.

[StuartMoxham]

Start with the recomended development time for TriX in d76. If you shoot roll film just bracket some exposure on the roll and look to see which negs you like the best for shadow detail. Then decide if the highlights are OK if they are too dense cut back the development by about 10-20 percent. Thats a fast way to get started. Or you could get Ansel Adams the Negative and do the proper tests to determin your personal exposure index.

[j._l._jones1]

<p>Much obfuscation can be easily cleared. Yes, exposure controls shadows (zone I specifically). Yes, development controls highlights. Yes it's improbable that your EI (exposure indices) will match the manufactures ASA rating, pardon, ISO. the procedure is based on a zone I exposure producing a 0.1 density above filmbase plus fog, and a zone VIII producing a 1.3 density above same.</p>

<p>A simple method of determining film speed and development with great accuracy while minimizing errors exists using only tools commonly found in the average well equipped darkroom. Other than the film and chemistry in question, all that is required is an enlarging meter (I use the white range setting of a Besler Colour analizer), one piece each of 0.1 and 1.0 ND stock (I like Kodak Wratten).</p>

<p>The procedure is straight forward and simple. Expose a dark target for a zone I exposure (targed should be out of focus, evenly lit and lit by a commonly used light source). Make exposures at 1/3 stop increments above and below for one to two full stops, perhaps three below, but not usually necessary. Begin with an f stop in the middle of the lens range where they tend to be most accurate, and make no shutter changes, in order to eliminate that variable. Ensure you make good notes. Develop this/these film/films for the recommended time in the developer of choice, or a good guess if experimenting. It's hard to over develop at this point. Also, develop an unexposed sheet or insure there's and unexposed area on the roll.</p>

<p>Once dried, warm up the enlarger head ensuring a consistent light output and place the enlarging meter below the lens, on or near the lens axis. Do not change the enlarger settings during the test. Place the unexposed film and one thickness of 0.1 ND stock over the meter sensor and zero the meter. Then, remove the film and ND stock and read the exposed negatives until you find the one which reads zero. It's corresponding IE is <strong>YOUR</strong> proper film speed.</p>

<p>Now, using your new film speed, shoot a white subject exposed for zone VIII. Expose several sheets or a whole roll. Develop one sheet, or a small piece of the roll for the recommended time. Once dry, calibrate the exposure meter to zero as before, this time using the unexposed and developed film and one thickness of 1.0 ND and three thicknesses of the 0.1 ND (I use a two by two Wratten filter cut into thirds). Remove the calibration material and meter the negative. If it's too thin, increase development time by ten percent and try again until correct. If too dense, reduce by ten percent and try again until correct. That's all there is to it.</p>

<p>Of course it goes without saying, you must be <strong>ABSOLUTELY</strong> consistent with your development technique and chemistry or all is for naught. The procedure is much less cumbersome than it seems and quickly becomes intuitive. Once you calibrate your film, equipment and technique, your photographs will come alive and delight you.</p>