How much dimmer on the ground glass is an f/9 lens vs a f/5.6? Or f/5.6 vs f/4.5?

[lenicolas]

I think more than the brightness of the lens it depends on the contrast of your subject and how magnified your subject is.
I have an easier time focusing a portrait under contrasting modelling lights with my 480mm f/9 than a moody landscape with my 75mm f/4.5...
Of course all things being equal, a fast lens is much more comfortable to use. My 210mm f/4.5 is my most used lens because it’s just so nice to compose and focus with.

I have the 45N2 and with a 300mm at full extension I can do a head and shoulder portrait on 4x5, so on 6x9 you should be able to do headshots.

[abruzzi]

I can’t see much difference between my 75mm f4.5 and my 90mm f5.6. I can see the difference between the 90mm f5.6 and my 105mm f8. Nontheless, the f8 is still pretty usable under a dark cloth. (Actually, everything where I shoot requires a dark cloth.)

[Mark Sawyer]

If you can find access to someone's view camera (since you don't have one yet), just set the lens at different apertures and compare focusing and brightness.

[maltfalc]

Thank you!

I wanted to do outdoor macro/close-up work with a 180mm f/9, would I have to worry? I know that lots of bellows extension also results in a dimmer ground

1:1 will turn your f/9 into an f/18. if you've got a camera handy try using the viewfinder at f/18.

[Tin Can]

Isn't fstop theory that all lenses at infinity focus with the same aperture, such as f8 will have the same 'light' on GG and make the same exposure on film?

That's why I use a meter to tell me so...

[BrianShaw]

If you can find access to someone's view camera (since you don't have one yet), just set the lens at different apertures and compare focusing and brightness.

Or do the same with a 35mm or MF camera with lens stopped down.

[Oslolens]

This is also brings me to a second question: How close can I focus a 300mm lens with 395mm of bellows draw? I know I'll be fine at infinity.

According to graflex lens chart for Rodenstock Schneider Nikkor Calumet and Fujinon, Nikkor-M 300mm has 294mm from film to flange. Bellows draw for 1:1 is 294+294, 1:2 is 294+294/2 while 1:3 is 294+294/3.

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[Schuster_Shots]

Thank you all so much! This is very helpful.

[Alan Klein]

300mm f9 is much brighter than 90 f/4.5 or 75mm f/5.6 all other things remaining equal on my Chamonix 45H-1.

[Drew Wiley]

Several factors. First, how bright the scene itself might be. Second, how adjusted your eyes are to dimmer light. Wearing sunglasses helps until you are under the darkcloth. Some types of groundglass seem to work better than others, though I don't personally like fresnels or screen brighteners. Longer focal length lenses are easier to focus at smaller apertures than wide-angle ones. But outdoors, one or two stops difference of maximum aperture is generally no big deal if you have a decent magnifying loupe. I carry view lenses all the way from f/3.5 to f/11 max aperture, but mainly in the f/9 range. I don't have a problem composing or focussing with any of them.

There are obviously going to be certain exceptions to that, like if someone has poor eyesight. Or you might be shooting within the entrance of a cave, like I was yesterday. I did fine; but if it had been really dim I would have brought a little laser pointer to provide me with a bright beam spot to focus on.