So I recently bought a laser rangefinder for measuring distance, in order to perfectly get the hyperfocal distance and other uses. (And to use in conjunction with focus calculator apps like Lumariver DoF).
However, I'm not sure if I should use the rangefinder in Line-of-sight mode (the straight line distance) or the 'true range' mode that tells you just the horizontal distance (using an angle sensor and basic trigonometry).
I know modern lenses are designed to be 'flat field' so the focal plane is actually a flat plane parallel to the lens plane. But naturally, an uncorrected lens will actually create a focal field that is curved like a sphere. But I'm not sure if this is the case for older lenses like those for large format.
Does anyone know if most large format lenses are corrected to have a flat focal plane or not?
This would only make a difference if photographing things that are well above or below the camera when it's being pointed horizontally, which could be the case if photographing a building, or from on top of a hill.
Specifically, the lenses I have are:
- Nikon 90mm f/4.5 NIKKOR-SW (4x5)
- Schneider 240mm f/5.6 Apo-Symmar (8x10)
Update: After doing some additional reading, it seems like most lenses should be corrected for field curvature. There are lenses that are specially designed to be extremely flat, called 'flat field' lenses but I don't think they really exist for large format photography.
This wiki page describes what I'm talking about: https://en.wikipedia.org/wiki/Petzval_field_curvature
A notable thing from there is that apparently stopping down the lense will reduce curvature, so if you're stopping down to like f/32 or f/64 that should help. Also it says that shorter focal lengths have a lot more curavture. Though I'm not sure if that's in absolute terms, or 35mm equivalent focal lengths. If not, it would seem the longer focal lengths used in LF would make it not as much of a problem.
Finally the best evidence I found is from Nikon's old brochure of large format lenses: https://galerie-photo.com/manuels/ni...%20cameras.pdf
On page 3 where it talks about Nikkor-W lenses, it says "Distortion, curvature of field and chromatic aberration are corrected to the high standards you'd expect from nikon". The way I read that, is that means some degree of field curvature is designed into basically all their lenses, but it's pointed out as being particularly good in that range of lenses.
Considering most large format lenses often have just as many lens groups as other more modern lenses, there surely must be field curvature correction in there.
Bookmarks