Sharpness - Mamiya C330

RolandRB wrote:

I'll have to rework the maths for depth of field to cover depth of field
at
the film side. Will post it when I get around to it.

It's called "depth of focus" on the film side.

Well, as expected someone has beaten me to it with the maths:

http://www.vanwalree.com/optics/dofderivation.html

I will put in the numbers and make a table. That should answer the
situation.

Pete

--
http://www.petezilla.co.uk

it flips out....it slips between two peices of metal...you snap
down...if you want screen out...you slide this lever and it flips
out.....the only 330 that is that way.....

wayne

On 12 Feb, 07:04, (MIRROR IMAGE PHOTOGRAPHY)
wrote:
it flips out....it slips between two peices of metal...you snap
down...if you want screen out...you slide this lever and it flips
out.....the only 330 that is that way.....

wayne

Is there some way of adjusting its position such as screws?

Peter Chant wrote:


Well, as expected someone has beaten me to it with the maths:

http://www.vanwalree.com/optics/dofderivation.html


Hmm - I'll have to read from the start - I get the impression that the
entrance and exit pupil diameters are applicable to something like
microscopy rather than photography - though it is all optics. Maybe a
little reading is needed.

I will put in the numbers and make a table. That should answer the
situation.

OK, doing my own calculations from first principles it appears, for a
subject at infinity that:

Depth of focus = 2 x circle of confusion x aperture

I'll have to stick up the calculations on the web so people can comment. It
is fairly simple stuff using similar triangles and I cannot see any
mistake. Rather surprised to see the lens focal length cancel out.

From this, with a 0.06mm circle of confusion we get:

f DoFocus (mm)
2.8 0.34
3.5 0.42
4.0 0.48
5.6 0.67
8.0 0.96
11.0 1.32
16 1.92
22 2.64
32 3.84

Might be worth having another look at the maths - I may have over simplified
the situation. (No I certainly did not look at diffraction limits).

This is interesting as if you compare a single f stop (and c of c) for a
range of focal lengths, the depth of focus as a percentage of focal length
is larger for wider (shorter focal length lenses) which makes the shorter
focal lengths less critical to focus in relative if not actual terms.

Therefore it does not matter which lens focal length you use to adjust the
focusing screen, just the maximum aperture. Suspect therefore that either
the 80mm for the C330 (largest aperture) or the most commonly lens used is
the a good one to use. Note that the C220 service manual states that a
standard lens (no indication of focal length) should be used:

"Standard lens: one whose lens back of the taking lens and viewing lens is
well adjusted"

Assume they mean any lens that is known to have good alignment between the
viewing and taking lenses.

I'll certainly re-check my alignment with several lenses to see what the
effect is.

Pete


--
http://www.petezilla.co.uk

no way to adjust it....need to find a good reair shop that knows what
they are doing and that will take the time......

Peter Chant wrote:

OK, doing my own calculations from first principles it appears, for a
subject at infinity that:

Depth of focus = 2 x circle of confusion x aperture

This calculation is correct, see:

http://www.rags-int-inc.com/PhotoTechStuff/DoF/

and scroll down to "Depth of Focus".

However, my assumed circle of confusion of 0.06mm is open to debate.

Pete


--
http://www.petezilla.co.uk