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).