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#111
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Sharpness - Mamiya C330 - IT WORKED
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 |
#112
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Sharpness - Mamiya C330 - IT WORKED
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 |
#113
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Sharpness - Mamiya C330 - IT WORKED
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? |
#114
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Sharpness - Mamiya C330 - IT WORKED
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 |
#115
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Sharpness - Mamiya C330 - IT WORKED
no way to adjust it....need to find a good reair shop that knows what
they are doing and that will take the time...... |
#116
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Sharpness - Mamiya C330 - IT WORKED
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 |
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