When shooting Tri-X

[kivis]

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When shooting Tri-X during the day I often move the ISO selector to 320 or even 240 on a sunny day then back to 400 for indoors and evening, all in one roll. Am I asking for trouble when I send it in for development to my lab? Are there any instructions different from standard?

[andybarton]

Tri-X is very flexible and tolerant film, but you will get much better results if you stick with one ISO. Film isn't designed to be used that way.

 

The lab can only process it for one speed, of course, so in effect you are just overexposing the film by 1/2 or 2/3 stop if they process it at 400, or underxposing it at 400 if they process it for 320.

 

In my experience, you will get the best results from Tri-X by exposing at 320 and developing for about 15% shorter time than recommened for 400. This opens up the shadows and retains the highlights.

[ndjambrose]

Yes - you are asking for trouble.

 

The development of a roll of film has to be consistent for the entire roll. You decide what ISO you want when you load it, and as long as it's developed for that same ISO then all your images will be as you metered and exposed. Anytime you deviate from that ISO with a given exposure, you are deliberately introducing some element of over or under exposure.

 

Fortunately the latitude of b+w film is pretty wide so in your pictures will still be usable. But you won't have well metered negatives with perfect density - they'll be some way from perfect, and possibly require some correction during scanning or printing.

 

If you need to control your exposures then use the aperture or shutter speed - not the ISO speed.

[Xmas]

Hi

 

It may be arbitary ideally you should use the (Weston Adams) Zone system to try and keep the shadow detail in the same part of the toe of the films response curve or just above.

 

The box speed has a 1.25 x safety factor of over exposure for 'normal contrast' subjects.

 

If the subject is very high contrast you need to decide do you want (good detail) in the highlghts or the shadows.

 

But lots of people don't bother to meter religiously...

 

Noel

[rob_x2004]

320 to 400 isnt that much difference, (nor is 240 if you know what you are doing but theres no point).

The problem is what you are doing with it.

You are overexposing in the bright light, while you probably (like many people) underexpose in low light.

Depending on your lenses, particularly modern sumilux which need a decent exposure, all other things being equal, you are creating double whammy problems.

Chances are whatever you have done will still find your subject within the exposure latitde of the film, but it is not a good habit to get in to:rolleyes:.

Personally, developing myself, I would box rate, then look at underdeveloping for scanning once I knew what was going on.

Sending it out I would box rate.

 

Ps ... Rather than ISO fiddle for Florida daylight where presumably you are running up against one thousandth, pick up a couple of el cheapo ND filters, work out which one is most successful then buy it in an expensive brand.

[tobey bilek]

Leave it at 200 ALWAYS and cut development 20% and you get a beautifully toned neg with grain that rivals TM100.

 

If you encounter flat (overcast) lighting outside, and are using ISO 400, you can safely overexpose it 1 stop.

 

It is a true 400 speed film that gives adaquate shadow detail at 400. Use it at 400 or cut development to compensate. Overexposure without development compensation makes for a grainy less sharp neg.