UKH

Trying to get my head around a film project I have that will almost certainly involve shooting in lower light than ideal even for ISO 800 film. I thought I had it - but I've managed to confuse myself again. If I have a roll of ISO 800 colour film, I can push it one stop by telling the camera body it's ISO 1600 and exposing correctly for ISO 1600...and then I tell the lab that I've shot the roll at ISO 1600? And in theory the end result will be a grainer film with more contrast and less detail in the shadows that is otherwise exposed 'correctly'? Whereas if I underexposed that frame a stop at ISO 800 and had it developed at ISO 800, I'd end up with a less dense negative, a loss of contrast and milky shadows? Have I understood that correctly?

I'd honestly just use Portra 400 and push it one stop in developing. Pushing colour film to the edge rarely works as well as it sounds like it should. If you do this and rate it at 800, you'll get away with underexposing the occasional shot and will have mostly decent colour. Give me a shout if you have problems with the negs and I'll drum scan a few for you. Portra 400 pushed one stop is better than 800 developed normally in my experience. Some places will push two stops but it's marginal returns and really mucky shadows. By the time you fix the shadows in post, they're still blocked up. Can you use a bit of fill light at all? Even the tiniest bit helps)

Tim

All emulsions react differently to processing and push-processing even more so. I would run a test strip and check that, and adjust accordingly. Its OK to process colour yourself as you have more control over the process so long as you maintain a consistent temperature. Another factor is to beware of reciprocity failure as you adjust ISO and timing for the development process. And i don't need to add that handling colour emulsions is far for testing and easier to f**k up.

Having said all this what's wrong with going digital?

I'm trying to get my head around the actual concept involved - I started tripping myself up in my head. That said, more reading done, I think I've got it. 

That's the impression that I was getting. 'Hi-fi' isn't necessary in this instance, but the image obviously does have to be usable. I was initially looking at something like Lomography Color Negative 800 or dubblefilm Cinema and pushing it one stop. I think 800 may well still prove to be too slow - but I'm just guessing at the minute, I haven't made a site visit to actually check.

That's a very kind offer, thank you

I found this while perusing for information - they seem to have come out remarkably well? https://canlasphotography.blogspot.com/2010/12/kodak-portra-400-miami-south...

I can probably get away with throwing a bit of key light on the subject, but  won't be able to light the background at all (which, in fairness, really isn't important).

For sure.

I think the subject would really suit film, and the technical challenges (low light, must be handheld, the specific logistics of this photo) are an interesting thought problem. It seems like a good project for learning.

it’s not just contrast, grain and shadow detail you need to worry about but also actual COLOUR. I’ve found in the past (admittedly different circumstances usually pushing ASA400 colour slide film two stops and shooting under tungsten light) that the colours become rather muted 

black and white will be much much easier. Ilford HP5+ or Fomapan 400, push two stops, lovely !

If it must be handheld (not even a monopod?) and must be colour (otherwise Ilford Delta 3200), then a faster lens? An f/1.4 or f/1.2 prime?

I just spied last night that the Nikon 55m f/1.2 isn't particularly expensive used, so I suspect that I'll  be acquiring one.

Alas,  the subject s very much a 'colour subject'.

It's worth remembering that Portra 400 has an extra stop in the shadows compared with nearly all other colour negative films so starting with this gets you a bonus stop in advance of pushing.