| Author | Message | ||
     Rj_ Tinkerer Username: Rj_ Post Number: 22 Registered: 08-2007 Rating: N/A |
Adding a little to Rick's post, I find that stopping down the aperture covers the focus point through the extended depth of field, in front of and beyond the focus point of the wide-open aperture. This finding would suggest that the opposite is true, and that your final image captured on the negative, would indeed be in focus with more stopping down of the aperture. On the condition that other variables, such as shutter speed and camera shake are controlled. The spherical aberration affects most lenses; even on modern Carl Zeiss f1.4 lenses for 35mm format, there is a significant focus shift at the wide-end of focussing, enough to result in focus error if the SLR/rangefinder technique of focussing is followed without compensation at maximum aperture. This focus shift improves with stopping down, and as Rick has pointed out, is a consequence of most lens design, particularly with the curvature of the front element of the lens at such a shallow depth of field. Still, it doesn't seem to explain the findings that are visible for you, and the position of the focussing screen, mirror, or any other implement in the viewing light path, in relation to the light path of the exposed image may need to be considered. How did the scan go? (Provided the image is scanned at an appropriate height from the scanner glass  ) |