Tag Archives: #diydeveloping

Still life successes

Using my antique (1900s) large format (10×8) bellows field camera I have been making some successful still life images.

I decided to move away from the uncontrolled variable light of the kitchen window to the fixed lights in my studio (dining room). This removed one variable from the exposure equation allowing me to make reliable test exposures on strips of the photo paper negative I am using. This saves the expense of wasting large sheets of photo paper on improperly exposed shots.

Whilst I am pretty happy that I can measure the light needed with my iphone app based on iso 6 for the paper negative, there are three other variables that come in to play.

1. At larger f stop values (smaller holes in the diaphragm) a small variance in position of the lever or ring setting the aperture has a disproportionately greater effect on the actual aperture used – at f64 on one lens a small tweak can make it effectively nearer f128 – doubling the required exposure time!

2. The bellows effect. Stretching the bellows past the focus length of the lens for close objects decreases the light intensity falling on the negative by an inverse square proportion. Doubling the distance decreases light intensity to a quarter. So 4x the exposure time is needed.

3. At longer exposure times, the longer the exposure the longer you need to achieve a set increase in darkening of the negative. So for a 2 minute calculated exposure I would expose for 2.3 minutes.

With these variables in play it pays to take a test exposure on strip of photo paper before committing to exposing a whole sheet.

For many of the still life images I am using a shorter (8″) focus length lens as this gives the greatest magnification. However it only stops down to f22,rather than the f64 of my other lenses, thus limiting the depth of field achievable. Accepting this limitation I have chosen subjects which do not demand a great depth of field – and am very pleased with the results.

I also added a graduated neutral density filter for the fennel photo to darken the bright base to get a more evenly exposed picture which seemed to work (see bottom photo).

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

Progress with The New Countess – 10×8 Camera

With some decent weather I have been able to take the “New Countess” into the garden and make some more trial images, testing out the lens and the exposure time variation with extending the bellows.

I am pleased to find that the combination of light metering with the I-phone app “Light & Exposure Meter” and adjusting for the bellows extension using measurements from “QuickDisc” (www.salzgeber.at/disc/)I was pretty successful with the images I made today. As always I like to push to the extremes – so after the pears image, some extreme contrasts with bright white table and chairs and then deep shadow for the surround of the bust.

I clearly have some work to do on managing the higher contrasts. I think I might have to expose for less and develop for more time. Anyway I am so pleases with the look and feel of these images from this camera. The Pears were shot at f11 and the table & chairs at f22. The bust was also f22 as I wanted to have a greater depth of field, but this wasn’t as deep as I had hoped – so will try again with f64.

NB – The images displayed here were made as paper negatives then digitised and made positives in Photoshop. The glossy Ilford paper was treated ISO6 and pre-flashed with an enlarger to reduce contrast.

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