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"rating" film

jeffreyg said:
Ralph, I agree with your "nitpick" but I was referring to his particular camera as the shutter speed may not actually be what it says on the dial, his developer ,etc. It's the end result that counts in the long run.
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You've got it! Well said.
 


So Ralph, since you like nitpicking....how do you explain Rollei R3? That's more than one ISO.
 
I always shoot at box speed and I don't really see any reason to make minor adjustments. Push processing is a whole other story.
 
exposure index 'EI'.[/QUOTE]

********
This is why correct terminology should apply. The ISO of a film speed is what the manufacturer says it is under a set of specific criteria.

If you decide to expose it at any other setting, you are using an Exposure Index, as Ralph says: not an ISO.

I believe that unless one completely understands the difference, one can not be at step one learning about film exposure.
 
Ektagraphic said:
I always shoot at box speed and I don't really see any reason to make minor adjustments. Push processing is a whole other story.
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The reason is an amazing improvement of shadow detail. My typical EI is about 2/3 f/stop slower than box speed.
 
fLOVE said:
It's a film that Rollei gives a relative ISO rating of 25-6400, one range with one developer, another range with a different developer.

http://www.freestylephoto.biz/40040...0-based-on-development-Single-Roll?cat_id=403
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Well I think they are mistaken and should put EI rather than ISO.
Rollei R3 is nominally a 200 ISO film when processed in a standard developer, the sort that other companies test films with; which are similar to D76 (I think)
Here is what they state in the PDF on the page you linked to:

'If you do not develop your own ROLLEI R³ film, you may entrust material exposed for ISO 200/24° to any “ordinary” processing outlet'
In other words this is an ISO 200 film that can be given variable EI depending on 'special' developers
The choice of other developers, would change speed like was mentioned previously- if Ilford used Microphen for Delta 400 they could call it Delta 500 that is how Rollei give a film speed spread which should read EI 25-6400 depending on developer.

When the ISO set the standards they used to require that the film was processed in a certain chemical developer, I think this changed recently so that a manufacturer just needs to state which developer gave the speed rating.
I think Fomapan 200 is rated at box speed in Microphen, effective speed with D76 is slightly lower and Ilford can call Delta 3200 rather than Delta 1000 (which is it's ISO in D76)
 
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I speculate that Rollei is bending the rules for the sake of simplicity and common understanding.

The ISO standard controls how film speed is determined, and (I think) only recommends a developer type without demanding a particular developer or dilution. In other words, it sets the procedure but leaves flexibility with the materials. If you use any other developer or dilution (which is likely), you will get a different film speed, and hence, we call it EI. This is the reason why an advertised film speed can only be seen as a starting point.

It has long been known that different developing agents, dilutions and agitation techniques produce different film speeds. To make matters worse, in the past, film speed have been measured at different densities in the toe area of the characteristic curve with different geometric methods. The ISO standard brought some clarity and uniformity but is implemented differently by different companies, so, some variation remains, and self-testing is a good idea.

It's my opinion that Rollei is ignoring much of this by showing a large range of exposure latitude as a range of film speeds. Those are two different things. Also, I'm sure that their film will not have the same shadow detail at the highest and the lowest speed, which adds the individual acceptance criteria for push and pull processing. Add different developers for high and low speed, and what you get is a large range of exposure possibilities, more or less sacrificing shadow (and maybe highlight) detail, but allowing the film to be adopted for different purposes. If I remember correctly, this film started as a traffic surveillance film in German speed cameras.

In so many words, Rollei is advertising a range of exposure indexes and exposure possibilities as ISO speeds. In their defence, maybe they do it to save themselves from explaining to customers what the difference is. After all, they are in the business of selling film and not in the business of photographic education, but strictly speaking, it is not correct.
 
Test for your own exposure index (EI) and development time instead of accepting what anyone else says.
Jim
 
Jim Noel said:
Test for your own exposure index (EI) and development time instead of accepting what anyone else says.
Jim
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******
And sometimes your EI and the ISO match.
 
Hmmmmm, vedy interesting!

Shooting with the Rollei TLRs, it doesn't matter what film speed I've got loaded (25, 125, 200, 400), I treat them all the same exposure-wise. I always set my DoF 1st, by using the DoF scale on the focusing knob, if need be, change the aperture/shutter speed to ensure no jitters, and then process it in Rodinal 1:50 for 10min standard temp/agitation.

Always comes out fine. Once difference is shooting Tri-X on occasion, and processing in HC-110 @ 1:50 also for 10min standard temp/agitation.

Since 1979, this system has never failed me. I don't use meters, just my eyes/brain.

Good luck with your shooting.
 

Say what? No matter what film, always the same exposure?
That doesn't sound like German precision to me?

Maybe, I misunderstood something here.
 
I think that one more thing has to be mentioned here. The paper.

In order to get your picture, you have to print it. If you do so chemically in a darkroom, you want to figure out what your paper is first. And what paper developer you use.
Once you are in tune with that paper and that developer, you can begin to mess with film and film developer.

The trick here to truly understand what's going on is to print your negatives often. As you do so, print different versions of one negative, some that are over exposed (lower exposure index than the ISO speed), some that are under exposed (higher exposure index than ISO, say EI 800 with 400 ISO film), and some that are box speed. See what happens. See what the limitations of your paper is.
When you understand those boundaries you can start to alter film development (mainly change agitation intervals and how vigorously you agitate, and based on those results adjust the time longer or shorter) to further tweak the results. Soon you will be able to compensate for different lighting scenarios in your development to suit the characteristics of your paper. Every time.

This approach will give you the full circle understanding of your whole system. The film and film developer is just a part of it.

What you're likely to see and feel is a new found freedom of expression where you don't have to worry about what things look like on the tail end. It will be an intuitive process, and you can start to use what you learned by over and under exposing / developing to make alterations to your process and push your materials beyond their limits in a creative way; you can begin to even use the weaknesses of your materials to your advantage.

View it as a system. And I love how Ralph described it as inputs and outputs.
 
keithwms said:
the tone curve (neg density versus exposure) is nonlinear... it has a quite linear central part, but then it has a "knee" and at the other end a "toe."
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This depends to some extent on the film. The curve for 400TMax is for all intents and purposes linear once you get past a log exposure of around -3.0 (when developed in TMax RS or D-76). The toe is very flat from approx. -3.5 to that point and then the slope of the curve changes abruptly and is virtually constant right out to a density of >3.0. That part after the toe is all we care about and there is only a barely perceptible shoulder.

Kodak's films seem to be a lot more linear now than they were in the past.
 
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