“F8 and be there” is the old maxim of press photographers. It means basically turn up and get a picture. An aperture of f8 would be in the sweet spot of the lenses performance and would guarantee a sharp contrasty image if you found the focus. I’ve been thinking quite a bit about focusing and optimum sharpness of late.
What is acceptable sharpness? What is an acceptable in focus hit rate with an autofocus camera? Why do some manufacturers have a reputation for excellent AF performance (Canon’s dual pixel technology) and some seem to be the bench mark for woeful autofocus (Panasonic’s DFD contrast based system)? I grew up with manual focus cameras and with them any failings were down to the operator. I remember getting my first AF camera – a Pentax SFX. The AF was slow really slow, glaciers move faster, and the noise of the motor made people stop and stare. I got rid of it quick smart and went back to using my manual focus Olympus SLRs up until 2004. It was the development of autofocus cameras in the 1980’s that saw photography as a hobby become more mainstream as out of focus photos were one of the things that put people off.
This thinking about autofocus came about because I’ve been reading and watching reviews about the Sony A7 iv *. There seems to be a vocal few criticising its auto focus performance in a very specific usage scenario. The users are using eye detect auto focus on a moving person with fast lenses such as the Sony 135mm f1.8 wide open at a distance of 2m or more. The complaint being that the camera only hits focus on the iris around 70% of the time and the rest of the time front focuses on the eye lashes. Let’s unpack this. The camera is ONLY achieving a 70% hit rate. Hells bells and buckets of blood! My Canon 5d and 6d couldn’t do that. When I use manual focus I couldn’t do that. I had enough trouble accurately focusing quickly with my Olympus OM Zuiko 135mm f2.8 wide open. Mind you those old 135mm f2.8 lenses were often a bit soft wide open. It is staggering to me that firstly you’ve got a 135mm f1.8 lens that is tack sharp wide open and then you can combine it with a camera that is able to focus on the iris of a moving person at 2m with a 70 % success rate. Let’s look at this problem from another direction. Now according to the DOF calculator on Cambridge in Colour the DOF with that combination is 2cm. That means 1cm in front of the eye and 1 cm behind. That would mean that the eye would be in focus but the nose and ears would be blurred. Even if you used an aperture of f4 which 2 1/3 stops more DOF you still only have 5cm DOF. An aperture of f8 would give a DOF of 11cm which is sufficient to render a human head acceptably sharp. Why would you want to take a portrait where only the iris is in focus? The craze for taking photos with razor this depth of field has been with up for about 20 years now and the only reason I can why it endures is that it signifies status – the photographer has the ability to own very fast and expensive lenses.
Two of the Twentieth Century’s photographic titans had some things to say about sharpness. In 1998 at age 90 Henri Cartier-Bresson said to Helmut Newton: “sharpness is a bourgeois concept.”** For Bresson content and concept were everything and if you look at his images you can see some of them are a little soft. On the other side of the Atlantic in the United States Ansel Adams famously said “There is nothing worse than a sharp image of a fuzzy concept”. So for Adams who sought technical perfection on every level in his photographs saw that intention and content were more important. So focus and sharpness like many other facets of photography are secondary – they play a supportive role but are not the primary consideration.
The photos accompanying this piece were taken with a camera that does not have a lens. It is a 4×5 pinhole camera with a focal length of 150mm and an aperture of f256 which when using Ilford FP4 developed in Ilfosol 3 gives an amazing amount of detail and clarity considering that no lenses are involved. I like to think that it is my anti technology camera. No lens, no focusing, no shutter mechanism, no film advance, no metering, no viewfinder. A successful picture required a great deal of serendipity and that is part of its charm.
* Not getting one and the reason has nothing to do with the autofocus issue and everything to do with the weight of bag with camera, 28-70mm f2.8, 105mm f2.8 macro, 35mm f2.8, 20mm f2.8, 150-600mm f5-6.3 and ring flash.
** I had a student who said that Bresson himself was a bourgeois concept.