What is the difference between 100 ISO film and 400 ISO film?

Ottrdaemmerung

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Probably because shooting ISO 400 @ EI 800 requires only a one-stop push?
 

BetterSense

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How is grain size controlled in manufacture?

If larger grain size causes faster film, I assume that means it's harder to make grainy film than fine grained film. That doesn't seem quite right.
 

Mike Wilde

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I believe the emulsion pre coating solution is started by bring the pot to a saturated level at some critical temperature, and then 'ripening' i.e. holding it a some stable temperature to aloow the crystal sizes to grow.

This is gross simplification, but rather a way to understand how differnet sized grains could be formed.

I believe the challenge is to make it not self fogging, stable, and sensitize it at all colours, and still compatible in performance lot to lot.

There is a lot of inter vat blending of fast and slow in most emulsions, I think, and it is the ratio that determines the effective speed.

A purchase and read of the advertised 'Making Kodak Film' is a good start to understanding the complexity of this product that we accept as a given manufactured good.
 

Photo Engineer

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All of this has been described in detail in the Emulsion Making and Coating forum here on APUG. Basically, grain size is a function of addition time, holding time, reactant concentration, ingredients, and addenda among a few of the variables. Others are gelatin concentration and type, and the phase of the moon!

My book will give more detail on this than in the Forum here and in Bob's book. And yes, I am working on it. It is here in Word, on my screen behind my browser! I am editing page 124 right now.

PE
 

jp498

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I think tmax 400 and 100 act very differently in their results if you change only the exposure for a given scene and use the same developer, camera, lens, etc... Something about the curves, color sensitivity, contrast... They are different films that share the tmax name and Kodak high quality. 100 seems a little flatter, suitable for copy work but can also be made super contrasty as a substitute for tech pan. Both are quite versatile for various uses.

100 use can use caffenol-C without fogging. There are caffenol variants that can be used with higher speed films though.

In large format, I think (not speaking with certainty), Tmx has a uv blocking layer and tmy2 doesn't, and this is useful for alt process printing which require uv or sunlight to happen.

Few need the higher detail of tmx in LF (or MF for that matter). I am pleased with the fine grain of tmy2 and use that for just about everything in MF and LF.
 

markbarendt

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Rolleijoe

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Shawn Rahman said:
A little off topic here, but why is there no 800 speed B&W film? I've always been curious about that.
Click to expand...

Funny you should ask. Back in the '80s-'90s Foma used to make an 800 speed film, and it was really good. But that was before it's become the household name they are today.


Required no special processing, either.
 

2F/2F

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Shawn Rahman said:
A little off topic here, but why is there no 800 speed B&W film? I've always been curious about that.
Click to expand...

Delta 3200 and T-Max 3200 are both ISO 1000 speed films. That is only one notch faster than 800.

My question would be, "Why are there no b/w films faster than 1000?" Some "true" ISO 4000 or 8000 speed film would do me wonders with a lot of my shooting.
 

Photo Engineer

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You approach a limit in terms of keeping. The faster the film, the worse the keeping due to heat and radiation sensitivity.

Actually, a 24000 speed film is possible as posted here on APUG, but it has not gone forward.

PE
 

2F/2F

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Yes, I would expect to buy it fresh all right!
 

Newt_on_Swings

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I would love a 24000 speed film, then again im already too cheap to spring for 3200 speed lol
 
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