Re: Image sharpness and focus distance.

[simon nathan <simonwide@xxxxxxxxxxxxx>]

exactly, clayton!

Clayton Tume wrote:

> Since the circumference of a cylinder 30 feet away is vastly larger than
> a cylinder 20 feet away, the film will travel at the wrong rate for the
> shorter distance and be seen as soft or blurred inspite of the fact that
> this point fell within the limits of depth of field.

My experience has been that the image is not soft and blurred but tack
sharp!

I did an experiment with my Cirkut camera where I photographed a building
with the correct gear (62 teeth for 100 feet) for subject distance then
repeated it with the wrong gear (53 teeth for 8 feet) to see what the effect
would be.

In both images the building was similarly sharp, by eye I couldn't detect
any softness and the prints looked very similar but remember these are
contact prints so we don't get too hyped up over sharpness.

What did change was the building length

435mm long for correct gear

530mm long for short gear

I have noticed in a lot of old time Cirkut photos of groups, where the group
is placed closer than usual to the camera the faces are compressed (but
still sharp) from using an incorrect gear. The shortest standard gear
supplied with the camera is for 25 feet, so shooting a group any closer
gives a compressed  look because the camera isn't pulling enough film, this
being the opposite effect to my building shot.

Clayton