I take pictures on film and with direct lighting in front of black backgrounds or sometimes in direct sunlight. In both of these situations I want to sometimes cover parts of the subject in complete black for artistic purposes. Just taking some black cloth doesn't do the trick it still reflects too much light and therefor is visible as gray material on the photos. Any tips on what material to choose to increase the light swallowing effect?
Use something with a matte finish or matte fibres. Take a magnifying glass to a fabric store along with a light and something to take reflective light metering with.
Shiny synthetic fibres [and even some natural wools] might look black, but are at risk of casting bright specular reflections toward the camera which increases the apparent brightness.
You also want your masks to be as smooth and even in the scene as you can get them: Folds and wrinkles will be more likely to show in the second exposure than a smooth texture.
From there, the next step would be to adjust how you're metering: Use a spot meter off the black-masking you're putting in the image, and use zone-system like metering methods to drop it down to where you want it.
This process may also involve getting creative with supplemental lighting work to achieve the best results:
- Cast shadows on what you want dropped to black
- Use flash or reflectors to put more light where you need it.
The method may be further pushed by using a film with higher contrast.
However, depending on exactly what you are aiming for from an end result, a more practical option may be to mask and double expose in post rather than directly on the film.
[You have some totally clear frames kicking around from accidentally taking photos with a lens cap on or something, right? By going this route you haven't 'made a mistake', you've been stockpiling masking stock for post production work!]
If you want black, black velvet from the fabric shop does a really good job. Here is a sample tabletop, the full light is directly on it.
This was a ISO 200 f/8 photo with flash.
It is a better grade called dressmaking velvet, which does better than the cheaper grades. The fabric shop will know what you want. I don't know about using it in sunlight, try just one yard first. But any of it is vastly better under the lights than other fabrics or paper.
What you need, is Vantablack. This awesome material reflects only .04% of light - way too little to affect those silver halides. That being said, I don't think it's commercially available. Perhaps there's a similar knockoff on the market?
All daydreaming aside, instead of trying to block all light from reflecting off the object and being recorded...why not instead filter and block? For example, if you switched to orthochromatic film, then you know that red light isn't recorded by virtue of the film...so you need only use material that reflects red. Alternatively, use a filter that cuts a part of the spectrum, like a deep red filter, and then use a material that reflects green/blue. My hypothesis here is that it's easier to find a material that reflects just a color than to find one that reflects near to nothing.
Since you are masking out part of a staged subject and using a film camera, presumably with an SLR style through the lens viewfinder, how about just masking the lens with a black material?
A cutout on a cheap lens cap would work. Then only light from the desired subject matter even enters the camera.