Light Metering for Film Photography

August 22, 2020 4:14 PM

I just bought an old film camera and light meter after shooting digital my whole life. I have a specific question about how the light meter (Sekonic) specifies 1/10 stop increments alongside, say, shutter speed readings. Googling got me a little closer to understanding but it still isn’t clicking.

Okay, say I’m shooting on Portra 400.

Here’s what I’ve been doing in simple terms:

+ Set the meter ISO to 400. Nothing fancy like shooting over or under.
+ Set the aperture according to the needs of the photo I’m taking in regards to desires for focus/sharpness/DOF. Let’s say I set the meter to f/11.

So I take a reading (either ambient or spot) and the meter says a shutter speed of 125—but with a subscript of, say, 9.

As far as I understand it, that’s saying 125 plus 9/10 of a stop. This particular light meter has a running little graph of the shutter speed at the bottom of the screen. 1/125 and 9/10 a stop is displayed very nearly to 1/250. So how am I to use this information? Should I just shoot at 1/250? To complicate matters, what if the subscript was 5? Does this suggest that I could, if possible, go up a half-stop to f/13 but shoot at 1/125?

This all makes me realize shooting digital has kept me pretty ignorant about exposure! Please be kind :)

posted by baptismal to Sports, Hobbies, & Recreation (9 answers total)

When I shoot film, especially color film I always overexpose by just a little, so if you are getting light meter readings like this, I'd err on the side of the slower shutter speed to overexpose the film slightly. I would also just develop normally. Basically, the reason for this is because if you underexpose the film, color film doesn't handle that very well, but it's fine to overexpose it a tad because you get a little more details in the shadows.
posted by ruhroh at 4:20 PM on August 22, 2020 [4 favorites]

Ignore the under-over, it honestly doesn’t matter. C41 colour film is far more tolerant than people give it credit, you can underexpose or overexpose a long way in either direction before your image will become unusable. Before people had the kind of false precision that comes with expensive modern light meters—I’m talking as late as the 2000s—they used ones that went stops only, or used ones where the speeds didn’t really correspond to their camera (hello 1/100”!) and before that, did it by Sunny 16 and other rules of thumb. Precision is good for precision but for taking interesting photos, who cares.

(The exception is if you’re trying to get archival precise colour rendition on transparency, where it really does matter. But for that use film is obsolete and you should go back to digital)
posted by Fiasco da Gama at 4:22 PM on August 22, 2020 [2 favorites]

As was said above, I wouldn't sweat the fractional stops on the meter all that much unless you're using a film stock with a very narrow range of stops. Portra 400 is very forgiving and I wouldn't worry too much about it. That said, if you are dealing with a really contrasty scene and you're shooting negative film, don't forget to meter for the shadows.
posted by octothorpe at 4:43 PM on August 22, 2020 [1 favorite]

Nthing what is said above. Don't sweat it too much. Like ruhroh, I prefer to shoot colour film slightly overexposed as well. Especially if it is fresh Portra film (I shoot a lot of expired film which can be very unpredictable but interesting). What kind of camera are you using and what kind of subject matter?
posted by Ashwagandha at 5:08 PM on August 22, 2020 [1 favorite]

I agree, for negative film the latitude is so great even being a whole stop off isn't really that big of a deal. Light meters shouldn't be taken so literally, it's a tool for evaluating and making your own decision.

Fractional stop increments is something I've only ever paid attention to when working with studio lighting.
posted by bradbane at 7:26 PM on August 22, 2020 [1 favorite]

The light meter assumes you'd rather over expose a fractional stop rather than risk under exposing. But based on the film you are using and your subject and what you are trying to achieve, you may decide that underexposing a bit is the better route, to save details in the highlights for example.
posted by DarkForest at 5:36 AM on August 23, 2020 [1 favorite]

Whatever theory you are following it is a good idea to try bracketing a few exposures and compare the results to see what is working best.
posted by Lanark at 5:48 AM on August 23, 2020 [1 favorite]

All the cameras and light meters I ever used were designed to use whole f-stop numbers only, and that includes totally professional cameras like a Pentax Spotmatic. I did have a subjective feeling that some films were biased a little differently that others. Kodachorme seemed to return darker images than Ektachrome, for example. But that could be just me. Anyway, the first roll or two will naturally be experimental, and so bracketing, as recommended by Lanark, will teach you a lot.
posted by SemiSalt at 8:14 AM on August 23, 2020

Frankly unless I'm working with a flash, I just use a phone app called Light Meter and it's always worked out well for me. It has the advantage of always being in my pocket and I've found it to be accurate.
posted by octothorpe at 8:18 AM on August 23, 2020