Friday, January 9, 2009

How fast will a "fast lens" have to be nowadays?

Pentax K10D + Zeiss Planar 50/1.4

This photo was taken at the "1000 Santa Claus Exhibition" (!) , in Óbidos - Portugal, using available tungsten light at f1.4, 1/45 sec and ISO 280. Despite the large aperture, the image is acceptably sharp and the 1/45 sec shutter speed avoided shake-induced blur. The Planar 50/1.4 is my "fastest" lens.

It is interesting to think how "fast lenses", with a minimum f-number below 2.8, were considered essential for photographing in low light conditions up to recently. But with the currently available professional/advanced amateur DSLRs equipped with large size sensors (not the case of the K10D) and excellent high ISO performance, the concept of "fast lens" may well become outdated. Low light photography is now feasible using f-numbers above 2.8, using ISO 3200 or 6400. Of course, lower f-numbers imply even more light available, but I wonder if that justifies the extra cost of the glass. Narrower depth of field may still be an argument, but we all know how painful it is to obtain proper focus at f1.4...

PS: [June 2009] A recent post by Mike Johnston at The Online Photographer, provides a very interesting discussion on the subject of "what is fast lens."

1 comment:

Peaches N Curry said...

That's a good point that with high iso these days, fast glass is not that necessary, but what about the bokeh? I think 2.8 is about where manufacturers will go, and maybe the superzooms sticking to f4?