Lens problems with The New Countess

Today was time to take the New Countess full plate camera to Clevedon and try some images of the wonderful Victorian Pier. Shame it was so breezy – not ideal for longish exposures with a huge camera like this one!

With two slides I had 4 exposures to make. It was a good opportunity to try the (supposedly) F384 lens too as it was a good focus length (12 inches – 300mm ) for the job.IMG_2026

Bringing the exposed paper negatives home for developing, I found that the lens I was using – Rapid Aplanat No.3 Ser.D.F.8 (R.O.J.A. vorm. Emil Busch, Rathenow) – was not operating at the indicated F stops – see the title image!

I had tested it in the garden on the pear tree using the widest aperture with no problem – but at the indicated f90 it way over-exposed the image (Paper negative). I tried a couple of other lenses at the same time successfully so thought I’d make some measurements of the diaphragm aperture with digital callipers and calculate the theoretical f-stop  (dividing the focal length by the aperture diameter)

As the F stop numbers increase the variance between the indicated F stop and the calculated one increases greatly. Column headings are Focul length, Diameter (of aperture) in 100ths of an inch, The F stop indicated and the F stop calculated.

Screenshot 2019-10-09 at 16.16.14

Using a more familiar lens at F45 for a 2 second exposure I achieved a reasonable if (wind) shaken exposure.

pier-600dpi

Published by Oldparson.art

A dedicated photographer of the environment, weather, landscape and its inhabitants, I have assembled a collection of awe-inspiring images for this exhibition. Many in colour, but a number in black & white - a medium which suits my love of the dramatic in photography. Starting from these photographs, I have produced linocuts and woodcuts as well as sculptures in wood. Each of these inspired by what is seen on my many walks in the region and beyond. A passionate experimenter, I am enjoying working with antique cameras and alternative photographic processes to make images that are more about conveying feeling, emotion, memory than they are about being a pixel perfect record of a moment in in time.

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