F Stops For Portraits Questions

[ColonelKurtz]

Hello,
I'm wondering if the information I was given is correct, and that is that f11 in large format is the equivalent of f2.8 in 35mm...? Also, wondering what f-stop everyone has been making their portraits at, lately? I'm guessing that making portraits at f11 and "higher" (f16, etc) is a good rule of thumb...? (I realize there are no rules, but I haven't made many large format portraits, yet, and am trying to get a feel for where everyone is at, regarding these, f-stop wise). Thanks

[BLATT LAB]

the conversion depends on the size of your negative not just "in large format". So it matters if you use 4x5, 8x10, 11x14 etc. and also the Focal length. A 150mm on 4x5 is roughly equivalent to a 50mm on 35mm Film but has the depth of field of a 150mm on 35mm. lets say this lens has a aperture of 5.6 then the depth of field is equivalent to a 150mm 1.8 on 35mm Film but with a the same angle of view as a 50mm. To get the same angle of view on 8x10 you need a 300mm. When this lens also has an Aperture of 5.6 the depth of field is like a 300mm 0.9 on 35mm with the same field of view as a 50mm. The math goes on like this with bigger/ small formats and different lenses.
I have seen people use F5.6 on 8x10 but also F45 on 4x5 for portraits. Its only depends on your preferences what you use.

[Dann Corbit]

Naturally, all the answers are going to be "it depends."
If you have a fast lens and you are going for the creamy dreamy bokeh and he lens can do it, then open it up all the way. What if a gentleman is sitting at a grand piano and he is keen to have the instrument in the shot?
Or perhaps a lady has a really spectacular outfit and rhinestone shoes and tilt won't get everything into focus well enough?
If it is a family portrait and the lens is really fast, you won't get everything in focus opened all the way up.

A big reason for large format stuff is all the choices that you have. If there were a single answer for all things we could use a great big box camera with no focus, aperture, or tilt and just call it good.

So don't let the camera boss you. You boss the camera.

[lenicolas]

I'm wondering if the information I was given is correct, and that is that f11 in large format is the equivalent of f2.8 in 35mm...?

Assuming you mean 4x5, the math isn’t too far off.

My easy and oversimplified rule of thumb is this :
4x5 is 2x the focal length and aperture compared to 6x7
6x7 is 2x the focal length and aperture compared to 24x32 (I crop all my small format to a 4/3 ratio)

So a 210 @ f/11 on 4x5 would give the same-ish field of view and dof as a 105mm @f/5.6 on 6x7 and a 55mm @f/2.8 on 24x32.


That being said, my most often used apertures for portrait on 4x5 are f/8 and f/11.
On the one hand I don’t want to overwork my 360w strobes (even though recycling time is not a problem with large format) and if I’m mixing ambient light I want to keep my shutter speeds reasonable. I took a portrait of my son and there was a window in the frame : at f/8 I had to slow the shutter to 1/15s so the daylight outside would match my flash exposure inside.

[Bob Salomon]

Assuming you mean 4x5, the math isn’t too far off.

My easy and oversimplified rule of thumb is this :
4x5 is 2x the focal length and aperture compared to 6x7
6x7 is 2x the focal length and aperture compared to 24x32 (I crop all my small format to a 4/3 ratio)

So a 210 @ f/11 on 4x5 would give the same-ish field of view and dof as a 105mm @f/5.6 on 6x7 and a 55mm @f/2.8 on 24x32.


That being said, my most often used apertures for portrait on 4x5 are f/8 and f/11.
On the one hand I don’t want to overwork my 360w strobes (even though recycling time is not a problem with large format) and if I’m mixing ambient light I want to keep my shutter speeds reasonable. I took a portrait of my son and there was a window in the frame : at f/8 I had to slow the shutter to 1/15s so the daylight outside would match my flash exposure inside.

Except the smaller the negative the greater the magnification for a given print size thus the smaller the negative the smaller the circle of confusion.

[ic-racer]

f11 in large format is the equivalent of f2.8 in 35mm?

f11 on a 300mm lens is a bout 27mm
f2.8 on a 50mm lens is about 17mm

So, to answer the question; No. You would need to stop the 8x10 lens down to about f16 to get a similar aperture size.

[ColonelKurtz]

Sorry, should've specified: Using a 4x5 camera with a 150mm lens for portraits. Would love to see examples of portraits anyone has shot with a 4x5 camera, and the corresponding data for each. Thanks

[MAubrey]

If you want to experiment with how film format, aperture, distance, and magnification affects background out of focus blur, this website is fun:

https://www.howmuchblur.com/

Of course, you can't account for how lens design affects the quality of said out of focus backgrounds!

[ColonelKurtz]

Thanks for sending... Although that looks to be for 35mm cameras, I'll have a look. I'm really interested in 4x5, as that is what I use. Thanks

[Bob Salomon]

Sorry, should've specified: Using a 4x5 camera with a 150mm lens for portraits. Would love to see examples of portraits anyone has shot with a 4x5 camera, and the corresponding data for each. Thanks

For head and shoulders to ¾ a 150 on 45 is much too short unless you like large noses, shoulders, foreheads, etc.