I have tried this as a shortcut to shooting film. Will it lead me astray ?
- Find a smooth white wall on a sunny day. Get a lens, remove the caps, open the diaphragm, and point it to a subject that contains a reflection of the sun. When in focus, the sun should be a very small white spot.
- Move the lens further away from the wall, and closer to the sun. The image on the wall will get larger, and the spot will now be a circular disk. If the disk looks like a ring, or has a ringed edge, you have bad bokeh. If the disk is not circular, you've got coma. If the disk is uniform, then you have nice bokeh. If the disk has very soft edges, you have very nice bokeh.
- Repeat the process by moving the lens closer to the wall than ideal focus. Now you have tested both regions of focus.
- Try the same thing with the lens stopped down. See how much the diaphragm blades affect the shape of the disk. If the disk is now shaped like a polygon, you've got bad bokeh. If the disk is still fairly uniform, you've got nice bokeh.
This gives rise to another question: Given that a diaphragm with many blades is desirable for this sort of thing: is there a way to replace the diaphragm of a modern lens, mounted in a stock shutter - while retaining the modern shutter ?
Bookmarks