Focusing on an f9 lens vs. and f 5.6 lens?

[sully75]

Simple enough question, what is focusing on an f9 lens like compared to an f5.6 lens? This is on a 5x7 camera if that's relevant. Which I don't think it is. But anyway.

Thanks
Paul

[David Aimone]

From my fairly limited experience so far, outdoors I don't notice much difference. Indoors, in lower light, f9 is certainly doable by a bit more of a challenge.

My Darlot Hemispherical lens starts at f11 and that's even a bit more challenging still.

[Ron Marshall]

It is easier to focus a dimmer image on a longer focal length. That said, I find a 90mm f8 is fine on 4x5 but a bit tough in the corners on 5x7.

But since the f4.5 version of the 90mm was twice the weight I put up with it.

What focal length are you considering?

[GPS]

Why not to try it with your own lens if you have one in f5.6 calibre? Close it down a little more than f8 and enjoy the reaction...

[goamules]

Simple enough question, what is focusing on an f9 lens like compared to an f5.6 lens? This is on a 5x7 camera if that's relevant. Which I don't think it is. But anyway.

Thanks
Paul

It's half as bright.

[vinny]

It's not always easy and I often wish I had all 5.6 or faster lenses. Heavy though.

[Heroique]

It is easier to focus a dimmer image on a longer focal length.

Yes, many of my compositions bear out Ron’s counter-intuitive (but physics-based) claim.

I’ve been in daylight situations where I’ve strained to focus dim corners (on 4x5) with my Schneider 110mm/5.6 – corners that I would be able to focus with greater ease if I had framed the same composition w/ my Fuji-A 240mm/9.

[Emmanuel BIGLER]

what is focusing on an f9 lens like compared to an f5.6 lens?

Hello from France !
Eventually the answer to the question might be closer to a physiological issue than a technical/optics issue, but both issues are intricated.

If you look at an image on a ground glass and if you are well-protected against stray light, your eye will eventually adapt.
People with an excellent vision will probably not notice anything difficult in focusing a slow lens, provided that they are comfortably installed to look a the image with no stray light. However people affected by myopia and astigmatism usually prefer brighter images.
Ease of focusing will depend on the contrast and sharpness of the image more than on its average brightness.
I use regularly different models of apo ronar lens in long focal lengths. I second Ron Marshall, longer focal length are easier to focus than wide-angle lenses. The contrast and sharpness of the apo ronar even wide-open à f/9 is excellent. Hence I've never found difficult to focus the apo-ronar, except in very dim light conditions indoors but I am not sure that focusing a 5.6 lens would have been really easier in the same conditions, although in principle the image is more than 2x brighter.

Conversely, old lenses that are not corrected to the same degree of perfection as the apo ronar can be difficult to focus, even if they are credited with a larger maximum aperture. Fuzziness in a bright image does not help a precise focusing, on the contrary.

Regarding the maximum aperture, I should add that I also have a 2.8 -100 mm planar lens for the 6x9 cm (2x3") format, well, used wide open for focusing, it really makes a difference w/respect to the f/9 apo ronar

[IanG]

Much depends on the quality of your screen and whether you use a fresnel. I found a visible (& measurable) 3 stop difference between two cameras/screens, and the dimmer one had an f4.5 lens the brighter an f5.6. With a new screen & a fresnel there's now just 1/2 stop differance.

An f9 lens isn't that bad on a decent screen, as others have said it's no worse than an f8 Wide angle, perhaps a little easier if it's a longer FL.

Some of us use far worse, I have an f16 Ross 151mm Surprisingly it's easy to focus on my 10x8 with a Beattie screen even in room lighting.

So check your screen that may be the weakest link. Beattie & Maxwell screens are expensive, some manufacturers like Wista & Linhof sell combinde screen/fresnels which are almost as good but a lot cheaper, I'm not sure what's available in 7x5 though.

Ian

[Jim Noel]

The f9 doesn't bother me at all, but my f18 does. If you have difficulty focusing it, lay a small flash light at the pinto of major focus and focus on it.