Pentax 560mm lens now listed on Adorama...any takers!

Started Nov 5, 2012 | Discussions thread
Avi Lewis Contributing Member • Posts: 659
Yes, a faster lens is preferable.

leopold wrote:

Well even with a faster lens you will need to stop the lens to f/5.6-8 to have some DOF anyway.

Shooting everything at f/4 will give you a thin DOF. I use my 400mm/4 always at f/5.6 and stop it down even more if needed but i don't use it at f/4 very often. With the new high ISO performance of the DSLR f/5.6 is not a problem.

I use to photograph wildlife in film days with an 400mm/5.6 with 100 ISO films (sometimes pushed to ISO 200) so now a "slower" lens is not a problem.

The first thing to keep in mind is that we compose and focus with the lens wide open; a faster lens gives a brighter, clearer image through the viewfinder, and by letting more light in (and because of the shallower DoF) make focusing, either auto- or manual, faster and more accurate, particularly early or late, under thick forest canopies, and in very dark, cloudy conditions.  Shooting at f/5.6 after focusing at f/2.8 is a different game than shooting at f/5.6 after focusing at f/5.6!  And all that's true no matter how well the the camera performs at higher ISOs.

Further, good technique will often allow shooting at wide apertures; knowing what to focus on and what can be allowed to go o.o.f. and shooting from the best angle to put the important parts of a subject on the same plane as much as possible.

Another consideration is that a faster lens will work better with a converter; sometimes the slower lens may not be compatible at all.

You may be happier with a smaller aperture lens, (which will probably be lighter and cheaper, but many, and I'm one, would prefer a faster lens.

Incidentally, also harking back to the days of film, standard "kit" lenses back them, (though we didn't call them that,) I'll remind you, were typically 50 or 55mm f/1.8s, and, in many cases f/1.4s would be offered.  The most common tele lenses were 135mm, and they were usually f/2.8's, although budget f/3.5's were also on offer.

Avi Lewis (

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