Desitometer apertures

[heidis]

I'm in the process of setting up a traditional darkroom, basically for b&w proce ssing and printing from both 120 and 4x5, and have a question re: densitometers that I've not seen discussed.

In users' opinions, what is the minimum useful aperture for a densitometer? I've seen their input areas range from .5mm to 4mm. Seems to me that the smaller inp ut area would be more precise, but on the other hand the D-max decreases along w ith the size of the aperture. How useful would you consider a unit with 4mm inpu t area, such as an X-rite 810? I'm aware that a smaller input area would be more useful on 120 than 4x5 film.

Thanks!

[Bill C]

>> In users' opinions, what is the minimum useful aperture for a densitometer? <<

Danny, I'd have to ask you, "useful for what?". If you were using color portrait films you might be trying to measure fleshtone highlight densities; on 120 film you'd probably want a 1mm or 2mm diameter aperture for this.

But since you're talking about B&W, I don't know what you'd be trying to measure that you might be worried about. If you want to use step wedges and read sensitometric curves you'd probably have large test patches, so a large aperture (ie, 4mm diameter or so) would probably be fine.

If there's something specific you're worried about, why not draw a circle whatever size you're considering on a piece of clear plastic, then hold that up to your negatives and see if it encompases the necessary area.

FWIW, I wouldn't worry too much about the densitometer having a problem as long as the aperture is a factory option; they'll be designed to handle it. If you're exceeding the readable limit of a densitometer, you probably don't want to spend the time printing!