View Full Version : How important is large aperture to short lenses?

Bruce Watson
23-Jun-2004, 19:29
This recent thread:


is interesting to me because like Mr. Butler, I too am interested in a lens in the 75mm category for backpacking with my 4x5.

One of the things I notice about these lenses is that modern lenses seem to have bigger apertures. Almost all of them are f/5.6 or better. My question is, why is this? What does the larger aperture bring to the party? I'm guessing that it helps with focusing. But I've never used a really short lens before, so it's only a guess.

What do you photographers who use really short lenses think about the importance of a big aperture in a short lens?

Pete Caluori
23-Jun-2004, 19:59

Largely the reason is it aids greatly in focusing. Not to say you can't focus an f8 lens, but a f5.6 is easier. The rear element on these short lenses is quite close to the ground glass, so light traveling to the corners has much further to go and the inverse square law takes effect. Another factor is the sharp angle that the light takes in hitting the glass off axis and this further makes the image darker.

Regards, Pete

Juergen Sattler
23-Jun-2004, 20:02
Pete beat me to the answer - it helps in focusing. WA lenses tend to have a lot of light fall off at the edges - you should also know that such an extreme WA lens will require a Center Filter most likely, unless you can live with the light fall off in the corners. These Center Filters are not cheap - around $300 at least.


Pete Caluori
23-Jun-2004, 20:08
I forgot to add that I have a few wide lenses some are f5.6 others f8. I use them both, but when I'm carrying them on my back and weight is a consideration, I usually grab the smaller, lighter f8 lens. I don't have a 75mm, but I have a 65, 72 & 90mm lenses.

Regards, Pete

Christian Olivet
23-Jun-2004, 21:01
You can use the wider aperture to make the depth of field shallower, if that is what you are seeking.

Gem Singer
23-Jun-2004, 21:05
Hi Hogarth,

The Nikon 75SW has a maximum aperature of f4.5 and takes a 67mm screw-in filter. The one I had was an extremely sharp lens. The wide maximum aperature enabled very bright focusing. I regret selling the Nikon, but the Fuji 75 f5.6 Fuji SWD that I replaced it with, runs a close second to the Nikon. I can recommend either one as a good 75mm lens for backpacking.

23-Jun-2004, 21:48
Large aperture is not so important so long as you are shooting in bright sunlight. But as the light decreases, focussing becomes exponentially more difficult, and eventually impossible. I never shoot with an aperture wider than f/16, opening wider only to compose and focus.

Jean-Louis Llech
24-Jun-2004, 04:33
"What do you photographers who use really short lenses think about the importance of a big aperture in a short lens?"

You are right, the larger aperture, the better focusing, as the image is clearer and easier to focus on the GG.
As I wrote on the thread you quoted, on the Master Technika, I often use the rangefinder for handheld shoots.
When using the rangefinder, the aperture is not a problem, as focusing is independent of the diaphragm, and you never use the lens at its full aperture, 4.5, 5.6 or 8.
Nevertheless, handheld, you need speeds between 1/500 and 1/60, and consequently a rather large aperture.
With lenses opening at f/8, the image on the groundglass is sometimes very dim, and hard to focus, even with an "improved" groundglass.
That's why a lens opening at 4,5 or 5,6 is always better.

Scott Soper
24-Jun-2004, 08:01
I use the older f8 Super Angulons (65, 75 & 90mm). The f8 isn't so bad shooting outdoors in decent light, but dimly lit indoor shots can be tricky. I'm quite happy with them for backpacking.

Chris Ellinger
25-Jun-2004, 10:30
Not only does the large aperture provide a brighter image for focusing, it decreases the depth of field to make changes in focus more apparent.