Multi ISOs on one film roll?

[adan]

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It is important to remember that "ISO" has a specific technical meaning.

 

It is the sensitivity rating such that an 18% gray card, underexposed 4 stops, will just barely produce a film density distinguishable from unexposed film (either viewing the film by eye, or in a direct chemical print).

 

In Zone System terminology - the speed for which a Zone V (medium gray) card can be exposed to Zone I and still just separate from "black."

 

The current ISO (International Standards Organization) technique is a bit different and involves logarithms and other math, but still defines a fixed shadow density (film base + fog + 0.1 when "medium gray" is exposed/standard-developed to a density of 0.9).

 

So you can't really expose a given film at different ISOs - the ISO (correct shadow density) is hard-wired into the film physics as tested by the manufacturer with a standard development.

 

Photographers are, of course, free to change their meter to something other than the technical ISO value, thereby using an Exposure Index (EI) - for many reasons. Including shooting at different EIs on the same roll of film.

 

But EI is not the same as ISO.

[fotohuis]

If you are working with any RF camera it is very easy to expose multiple iso on one film.

 

I am also working in the zone system for my 35mm M7/Zorki and FED cameras. After making some exposures I make one blank exposure. Remove the lens, put the timer on B and lock it, open the shutter and put a small self adhesive sticker on the film surface. Then close the shutter, expose another blank and then going on another iso rate. You can do this "trick" several times on one 135-36 film and when doing your film development each piece of film is getting in its own Jobo 1510 developing tank incl. the notes which iso has been done. It is very easy with a scissor to cut straight on the sticker place. Then each part is developed in the right way, which is of course different in developing time. In this way you can have really perfect results in different harsh ligh contrast situations on any B&W film.

 

To do this trick with any SLR is very tricky due to the mirror inside this type of cameras, so better not.

[pico]

I am also working in the zone system for my 35mm M7/Zorki and FED cameras.

 

Wow, what a lot of trouble! Consider getting an Exacta with its built-in film slicer, or a Contaflex with interchangeable backs, or even Leica OLEYO-OLETO.

[fotohuis]

A Contaflex is not a Leica .....

 

However if I win the next lotery I will certainly buy 2 extra M7 bodie's.

[pico]

A Contaflex is not a Leica .....

 

 

 

However if I win the next lotery I will certainly buy 2 extra M7 bodie's.

 

 

If you won the lottery I will sell you my two M7 bodies at half the going rate. I will not be using them for long. (They are to me Leica's masterpiece.)

[philipus]

My apologies for the delay in posting back, but here are some examples from a party. When I shot this with my M3 I didn't pay attention to exposure at all but just picked apertures based on what I wanted or was felt needed (though usually it was between 1.4 and 4) and a shutter speed to ensure sharpish images. The surroundings were often really quite dim but there were also strong light sources (which also messed with colour balance; I struggled a little with that in post). The film was developed at 400 but many frames were shot at EI1600 or perhaps even more in some cases. All in all, the results were acceptable for a private social occasion I thought. I'll post a few more in a second post.

 

Philip

 

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Sorry, Philip, crossed posts - I would be interested as well to see some examples, playing around with Portra, I stayed on the lower side of one stop variation so far. Once, I exposed a roll of Portra 160 @ 400 by mistake and found the results unusable.

 

Stefan

[philipus]

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Here are a few more to show a variety of lighting situations.

 

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[NJH]

Its funny that this multi ISO myth thing is usually claimed for XP2 whereas IMHE Portra 400 does a much better job holding on at 800 or more, I really don't like XP2 at 800 whereas it seems fine down at 200.

[chrism]

I usually expose XP2 at 200 for stand development in Rodinal, and had got halfway through a roll when I realised I had some Ektar 100 to develop as well. So I finished the XP2 at 400 and put them both in the same tank and used a Unicolor kit in standard fashion. All came out just fine, but I do note the XP2 negs are a bit less contrasty than when developed in Rodinal.

 

I did happen to make my usual hash of getting the pair of 120 films on steel reels inside a changing bag (I used them as I have 1 litre of Unicolor chemicals and for both films to be adequately covered in the same tank a tall narrow metal tank seemed to be in order.) Next time I will simply put them both on the same Paterson reel.

 

Chris

[kivis]

There a couple 35mm cameras that allow you to change to different ISO films mid-roll, for example a Contax and Exacta but no Leicas. There is one 70mm rangefinder that allowed it as well, but that's not what you asked about.

 

Every other 'solution' is a kludge. You have already read them above.

.

What? I can change ISO with any camera including Leica. I routinely change ISO's in one roll of film with any C41 film. Works quite nice with Ilford XP2 and Kodak Ultra Color. I often change to 200 to increase contrast on a sunny day, then back to 400 when in the shade and then up to 800 for a poorly lit indoor shot.

[andybarton]

What you are actually doing is under- or over-exposing the shots on the roll. In exposure terms, adjusting the ISO on the meter is no different from opening or closing the aperture a stop or two.

 

ONLY if you mark and cut and process the film differently are you actually changing the ISO. [Correction - you are not changing anything with regards to the film (which is a physical thing with inherent characteristics), but you would be changing the way that it is processed, in order to rate the film at a higher or lower speed than its base speed]

 

C41 films are very forgiving of under- and over-exposure, which is why you can achieve acceptable results, even if a couple of stops either side of the norm.

[gyoung]

This thread seems to go round in circles, based on misconceptions.

 

Film speed is a scientific measurement based on the amount of light exposure required to achieve a density 0.1 above base fog level.

It is affected by processing, some developers producing higher, some lower speeds depending on how they work. (But not simplisticly increasing development time to increase speed, that only increases contrast at the expense of shadow detail).

There is ONLY one 'correct' speed for any set of conditions of film/development.

What you are doing by 'changing iso on a roll in the camera' is taking advantage of the latitude of an emulsion to cope with varying amounts of under or overexposure, and is also affected by the sometimes inability of a film to cope with the brightness range of a subject, so you need to decide whether to sacrifice shadow or highlight detail by giving less or more exposure respectively than the one measured by 'normal' methods.

 

In contrast to the measurement of film speed, deciding on an exposure to give a photo is an art form, based on knowledge of materials and equipment, and experience of previous use, to get the results you want. A short course in basic sensitometry is a distinct advantage, IMHO, to full understanding of the media you are using.

 

Gerry, the older bloke who did a C&G in photography a LONG time ago!

[tobey bilek]

There is but one iso for a particular film/developer for optimum results.

 

Different iso one a single roll is simply over/under exposure and one can deal with that and get a photo, not one that is optimum.

 

The only exception is a pull processed roll, one stop over and cut time in developer 20%. Richer shadows result and less burned highlights in high contrast scene.

I know wedding photogs who deal with black tux and white dresses and results are superb.

 

Sone techniques I have successfully used with problem negs are dye dodging ( Kodak new Cocine), print flashing, and contrast masks, split contrast filter printing, divided print developers, soft and hard contrast baths, and switching from condenser to diffusion enlarger. All this is too much work, so make a good neg to start with.