Focal length vs. field of view?

[Bob Salomon]

It matters if you're comparing dramatically different formats, doesn't it? The magnification required for the framing gets less and as format gets smaller?

You might want 1:4 for an 8x10 portrait, but you certainly wouldn't want that for 120 film or 35mm and the extension affects image less and less.

No, portraits are usually taken at about the same distances, regardless of format. If you are using lenses appropriate for portraiture for each format.
You want to be close enough to the subject to direct them and relate to them. Except for some environmental distant portraits.

[Pere Casals]

The normal lens for a format is the length of the format’s diagonal, or close to it. Period!

Bob, the definition of normal lens is a bit more loose: "a normal lens is a lens that reproduces a field of view that appears "natural" to a human observer". https://en.wikipedia.org/wiki/Normal_lens

yes, "typical" used values are the diagonals, to guess what it will be "natural".

But a 150mm LF lens for portraiture looks longer than "natural", because that, you know it very well, some consider 135mm also a normal focal for 4x5.



Analyze next situation:

Imagine we shot a landscape with normal (I.F.) lens for the 35mm camera and a with view camera lens that takes horitzontally the same field, exactly same mountains in the image.

But as we make a close shot, with same distance for both cameras it will happen that the LF camera will take less horizontally because image growth upon additional bellows extension.

There we have a discrepance, depending on if we account for focus breath or not.

doesn't the circle grow when focusing near ? Well, the aparent focal grows proportionally the same than the circle !

This is because in (45) LF "normal" is between 135 and 150, depending on subject distance

[Leigh]

Shooting distance and focal length for portraits are chosen to make the image look "normal".
They both depend critically on the format in use.

You don't want the focal length too short because the nose looks too large relative to the ears.
You don't want the focal length too long because the whole face looks flat.

- Leigh

[Pfsor]

Bob, the definition of normal lens is a bit more loose: "a normal lens is a lens that reproduces a field of view that appears "natural" to a human observer". https://en.wikipedia.org/wiki/Normal_lens

Yes, the "natural" field of view - but with the lens focused at infinity!! Otherwise any shorter lens can be the normal one, if focused at a more or less distant subject and you cannot have 10 different normal lenses than are normal just for a certain focusing distance! You got it?

[Pere Casals]

Yes, the "natural" field of view - but with the lens focused at infinity!! Otherwise any shorter lens can be the normal one, if focused at a more or less distant subject and you cannot have 10 different normal lenses than are normal just for a certain focusing distance! You got it?

Professor, what in fact is "normal" (or not) isn't the lens itself, but the angle of view of the whole system. You may know that the angle of view of a view camera changes with bellows draw... so it's about that.

I'm pretty sure that Bob has sold truckloads of 150mm sironars, not extrange, a 150mm delivers a great natural look for general photography, and a great longer than normal look for close half body portraiture... so perhaps it's the most useful (45) LF glass !!!

Anyway YK used the 14" for 810, what it would be a 180mm for 45.

Shooting distance and focal length for portraits are chosen to make the image look "normal".
They both depend critically on the format in use.

You don't want the focal length too short because the nose looks too large relative to the ears.
You don't want the focal length too long because the whole face looks flat.

- Leigh

Beyond exceptions, we may want to shot a portrait from some 3m, to prevent a "nose job", and then we pick the glass that from that distance it frames what we want, isn't it ?

[Pfsor]

Professor, what in fact is "normal" (or not) isn't the lens itself, but the angle of view of the whole system. You may know that the angle of view of a view camera changes with bellows draw... so it's about that.

Pere, don't try to mud the waters - a lens gives a certain AOV on a film format. The AOV that it gives when focused at infinity defines or not the "normality" of the lens for the given format.
If you want to introduce there the fact that shorter lenses, focused on a closer distance can simulate the AOV of longer lenses focused at infinity you just throw the normal lens definition out of the window.

Yes, Pere has found out that a 75mm lens focused at a close up distance can give the same AOV as a 150mm lens focused at infinity. Therefore, Pere says, the 75mm lens is the normal lens in this case! Bravo! Now we can easily compare normal lenses for different formats - by choosing the focusing distance that gives a normal AOV of different lenses.
Good grief!

[Bob Salomon]

Professor, what in fact is "normal" (or not) isn't the lens itself, but the angle of view of the whole system. You may know that the angle of view of a view camera changes with bellows draw... so it's about that.

I'm pretty sure that Bob has sold truckloads of 150mm sironars, not extrange, a 150mm delivers a great natural look for general photography, and a great longer than normal look for close half body portraiture... so perhaps it's the most useful (45) LF glass !!!

Anyway YK used the 14" for 810, what it would be a 180mm for 45.





Beyond exceptions, we may want to shot a portrait from some 3m, to prevent a "nose job", and then we pick the glass that from that distance it frames what we want, isn't it ?

No, for classic portraiture you need the depth of field that holds resolution from the tip of the nose to the base of the ear. That means you focus on the base of the nose and dof covers the range.

That range will be controlled by the focal length of the lens and the film to subject distance.

At no time is the angle of view considered.

The above is for head and shoulder portraits.

You might vary this in situations where you want to include additional info, say a company logo in the background but, again, it is not the angle of view, it is focal length, distance and dof that the pro considers.

[Leigh]

No, for classic portraiture you need the depth of field that holds resolution from the tip of the nose to the base of the ear. That means you focus on the base of the nose and dof covers the range.
That range will be controlled by the focal length of the lens and the film to subject distance.
At no time is the angle of view considered.
The above is for head and shoulder portraits.

Yep.

That's what we taught in photography school.

- Leigh

[tgtaylor]

I get practically the same FOV with my 150mm F5.6 Rodenstock Apo-Sirona s on a 4x5 as I get with the 120mm Nikkor SW, 75mm SMC Pentax 67 on a Pentax 67II, or with a 35mm Nikkor lens on the F6. There is a small - barely discernable = difference between the 4 FOV's but that difference is insignificant. If memory serves me correctly, the AOV on the Rodenstock is "a whopping 105°" which is how B&H put it at the time.


Thomas

[Bob Salomon]

I get practically the same FOV with my 150mm F5.6 Rodenstock Apo-Sirona s on a 4x5 as I get with the 120mm Nikkor SW, 75mm SMC Pentax 67 on a Pentax 67II, or with a 35mm Nikkor lens on the F6. There is a small - barely discernable = difference between the 4 FOV's but that difference is insignificant. If memory serves me correctly, the AOV on the Rodenstock is "a whopping 105°" which is how B&H put it at the time.


Thomas

Angle of view of a Rodenstock Apo Sironar S is 78°; 80° for an Apo Sironar or Apo Sironar W; 72° for the Apo Sironar N. On the longest lenses aov is slightly reduced due to the size of the shutter opening.
No Sironar, of any type is 100° or greater. That would be Grandagon,Grandagon N and Apo Grandagon series lenses.