Ensign Greyhound apertures ??

[Agulliver]

Does anyone know what the apertures in the Ensign Greyhound camera are? I believe this camera is almost identical to the Ensign All Distance Folding Camera and both date from circa 1930. They have three apertures "small, medium, large" and the advice is to use the small for "B" exposures, medium on sunny days and large on cloudy days. Shutter speed is approx 1/30s. I've searched and cannot find anyone who's ascertained what the f numbers are for these models.

I've run a couple of films through mine but nothing to actually figure out what the apertures might be.

 

[Ian Grant]

It's not in the 1930 BJPA advert or in new goods, I suspect the lens is no faster than about f7.7/f8. It's a bottom end model so unlikely to be in BJPA adverts, but I'll check 1931, 2 & 3 when I'm in the darkroom later.

A comparable Kodak camera size wise(in terms of lens as well) has an f8 lens.

Ian

 

[Agulliver]

Thanks! It's definitely a low end camera but it works and I'm curious how much light I need with various film speeds.

 

[Ian Grant]

The camera was made in the era of thick emulsions like Ensign Speedy, Verichrome and Ilford Selochrome which had far wider exposure latitude than modern films.

It's not generally realised that Houghton Butcher were actually a large scale manufacturer of film, Butcher Film services Ltd were distributors of American and British films, they supplied the print film copies for the reels sent to cinemas, the Premier Film Printing Co., Ltd was also part of the group. They also worked in partnership with independent film producers in the UK.

Ian

 

[John Koehrer]

If you know the focal length of the lens, put a scale across the front of it and measure it. With the glass in place please.
Divide the fl by diameter measured and that's the f #. Obviously with three apertures ya gots to do the math three times.

There's another user here that's going to say take the front elements off first but that's him.

 

[shutterfinger]

For lens of that vintage focus infinity at the film plane then measure the distance from the aperture/shutter blades to the film plane for an approximation of the lens focal length. The rear nodal point of the lens is close to the aperture blades and is the point of reference for focal length. Aperture (f stop number) is the lens focal length divided by the diameter of the entrance pupil. The entrance pupil is the diameter of the aperture opening when viewed through the front of the lens.
Ad in a 1913 American Annual of Photography:

 

[villagephotog]

If you know the focal length of the lens, put a scale across the front of it and measure it.

As shutterfinger mentioned, the f-number is the lens focal length divided by the entrance pupil diameter, and the entrance pupil is not a real physical phenomenon. Again as shutterfinger noted, it's the virtual image of the aperture as seen through the front of the lens.

I mention it only because it helps to know exactly what to measure with your ruler. You can get a reasonably accurate estimate of entrance pupil diameter that way on most lenses that I've played with — probably accurate enough for the OP's purposes. But you can't get a precisely accurate measurement of entrance pupil diameter with a ruler, or at least I can't.