Large Format Diaries
Benefits of Bellows
Rather a long time since I last wrote a post about my experiences with large format. As you may have seen from the gallery, things have been going rather well. Trips over the last 6 months or so to Glencoe, Wales, and Derbyshire have provided numerous and various opportunities for the growth and development, and enjoyment, of the skills required and insights provided with this very different method of shooting. My plan for this year was to work harder with film, and I estimate that over one third of the successful images I’ve made this year have been on film – that is a pleasing statistic given the radical difference between the speed at which one can work with digital and large format – though the Canon A-1 has had a few outings recently too.
The present post is an introductory explanation of one of the benefits of shooting with a large format camera (or indeed any camera that uses bellows focusing), and an aspect of it that is not very often mentioned.
Bellows factor or compensation is, it seems, often considered as a technical pain in the neck when shooting: one more thing to remember that affects the exposure time, one more thing to forget about, one more mistake waiting to happen. My enhanced labelling of my large-format film holder tapes system has been pretty successful lately in reminding me of all this little things that affect exposures, so this isn’t too much of a factor for me now, touch wood. Here is what my labels look like (they get stuck to the film holders across the top, providing extra security to prevent accidental light-leaks, providing ‘exif-data’, but also now reminding me, before shooting, of the importance of noting bellows and filtration in the exposure calculation (once filled in in the field they don’t look this neat, but you get the idea):
In essence, bellows-focusing lenses can extend beyond infinity, to become more like macro lenses, depending upon the focal length (or virtual focal length) and amount of bellows extension you add on. What’s great about this is that this works exactly the same for any focal lengths, meaning that you have massively enhanced macro-like tilt-shift lenses at all focal lengths, with limitations only created by lens image-circles and stability at longer extensions. In practice, I have extended the bellows beyond infinity for shots with all my large format lenses from normal to telephoto – 150mm, 210mm, 300mm, 400mm. In fact, with the 400mm, the bellows extension required beyond infinity is shorter, because the Fujinon 400mm T f/8 lens is a telephoto design, so has a shorter infinity stop (255mm), meaning shorter bellows extensions in practice than the Nikkor 300mm M f/9, which isn’t a telephoto design and so needs racking out beyond 300mm for close-up work.
What I wanted to mention briefly here are the great advantages of this flexibility. I also wanted to mention the difficulties I have with this way of working, which, so far at least, requires trial and error regarding the lens required.
The great flexibility is that you can do close-up work at a variety of different working distances. Here is a shot where, if I remember, the scene is probably about 30cm-50cm high, and I was shooting from a distance of about a couple of meters away. This was necessary, because the terrain underfoot was old quarry rubble, so getting any closer with the tripod was impossible. Shot at 300mm, with 350mm bellows and both front tilt and swing.
Here is another image, where I worked with a shorter lens, but with a much closer working distance – perhaps about a couple of feet. Shot at 210mm, with 340mm bellows and lots of front tilt and rear rise. Here the subject isn’t very much bigger than the film size: still not 1:1 but getting closer.
So: working distance is as much of a factor – but is dealt with even more flexibly – with large format as in macro photography with a DSLR. Anyone who has shot with both a 60mm macro and a 200mm macro on a DSLR will understand what I’m talking about: no one in their right mind would shoot butterflies at 60mm.
The only difficulty I’ve found so far is pre-visualizing the relation between focal length and working distance: sometimes I’ve tried three different lenses for a given composition before I’ve worked out which one will work at a given distance. This is one aspect of working with a viewfinder (whether optical or an iphone app) doesn’t really help. I wonder whether there are any speedier solutions to this?
Thanks for reading,
Update regarding lens selection and bellows factor: it seems, if I understand correctly, that if you shoot 1:1 on large format, the subject to film-plane distance required is four times the focal length of the lens, using the optical mirror formula:
(1/working distance)+(1/bellows extension) = (1/lens focal length),
and where the total film plane to subject distance is the working distance + the bellows extension.
I suppose, then, that an estimation of subject distance will therefore help in taking some of the guesswork out of lens choice. Using the above formula for the two images shown, the working distance and total distance from subject to film-plane would therefore have been about 2.1 meters and 2.45 meters for the first, and 55cm and 89cm for the second, which seems right.