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View Full Version : Focusing on an f9 lens vs. and f 5.6 lens?



sully75
30-Sep-2010, 16:24
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
30-Sep-2010, 16:31
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
30-Sep-2010, 16:41
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
30-Sep-2010, 17:01
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
30-Sep-2010, 18:35
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
30-Sep-2010, 18:45
It's not always easy and I often wish I had all 5.6 or faster lenses. Heavy though.

Heroique
30-Sep-2010, 19:09
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
1-Oct-2010, 04:12
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 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
1-Oct-2010, 05:07
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 :D 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
1-Oct-2010, 08:35
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.

jan labij
1-Oct-2010, 09:05
Why not just turn on the headlights of the pinto and focus on that? I have used a camping style candle lantern located where I wanted to focus, and focusing on the flame.

Ken Lee
1-Oct-2010, 12:38
Shooting outdoors, my Fujinon A lenses (f/9) and APO Nikkor lenses (also f/9) have never been too dark for accurate focusing or composing. Even the 450mm Fujinon C, which is f/11.5, has never presented a problem.

Wider lenses are... appreciated, when shooting at close distances, under dim lighting, and indoors. When shooting at 1:1, an f/9 lens becomes an effective f/18 lens at its widest - because the required bellows draw has doubled. That's why we have to allow 2 extra f/stops at 1:1 extension.

Drew Wiley
1-Oct-2010, 13:15
Which specific lens choice and format is in question here? F/9 isn't made in just
anything. Obviously, something like f/9 is a pain in true wide-angle design; but in
something like a 70-degree normal lens used on a wider format it's not bad, and f/9
as a long lens in relation to the specific format is no problem at all outdoors. Like Ken,
I routinely use lenses in the f/8 to f/11.5 category, on both 4x5 and 8x10. Don't miss
those big old 5.6 plasmats at all!

Ken Lee
1-Oct-2010, 15:16
Process cameras don't care much about visibility, while photographers often do.

Process lenses are often f/9, simple 4-element designs with modest coverage.

Macro lenses are often f/5.6, and are modified versions of the f/5.6 plasmats we often use for landscape and general purpose imaging: they offer wide coverage and a bright image.

Fujinon A lenses are an exception: a plasmat design, but f/9. Wide coverage, but small, light, and small filters: perfect for outdoor work, especially if you need to travel light.

Ed Richards
1-Oct-2010, 15:33
It is not just brightness - DOF decreases with aperture and with lens length, so long lenses are easier to focus, even if dimmer. f4.5 90mm lenses focus easier than f8, even if the f8 was in a brighter environment so there was no illumination difference.

Drew Wiley
1-Oct-2010, 21:27
Ken - I would supplement what you state by noting how both Fuji A's and the very
similar Schneider G-Clarons are based upon a closeup formula for the plastmat,
but have been so refined that they achieve at least a 70-degree field as well as
superb performance even at infinity. However, only Fuji marketed the design as a
"super apochromat" and added multicoating. Performance-wise they are very similar
but with the Fuji having a little more contrast due to the multi-coating of the later
lenses. I tend to think of this as another step in the evolution of process lenses
themselves, though G-Clarons made specifically for process work and those made
for tabletop and general-purpose photography are slightly different designs. I was
once told by Schneider that it was this further refinement of the G-Claron which was
their motivation to discontinue the Kern dagor series as their premier taking lens.

John Kasaian
1-Oct-2010, 21:35
I've no problems with a 240 f/9 G Claron on my 8x10 under a rather heavy tree canopy. I have a 340 f/9 Artar on a 5x7 and it is pretty bright even indoors at night with ordinary incandescent lighting on the subject.

Brian Ellis
2-Oct-2010, 06:31
Depends in part on the focal length of the lens. F9 on a long lens - say 210 and up - is generally no big deal. F9 on a shorter lens can be problematic because so much of the light is striking the viewing screen at an oblique angle and therefor has farther to travel than light striking it more straight-on, as is the case with a longer lens.