Simple question about objectives. From the FAQ located here:
https://www.photomacrography.net/forum/ ... hp?t=12147
Is the statement:
The "160" designation actually corresponds to 150 mm from the objective to the sensor plane.
Is this designation particular to the make/model of the objective? Will it change from Nikon to Mitutoyo to other? Or for Nikon objectives, will it change from M Plan to other?
Or is it particular to the type of objective (finite vs. infinite)?
Or something else?
Microscope objective and distance to focal plane
Moderators: rjlittlefield, ChrisR, Chris S., Pau
Microscope objective and distance to focal plane
Best regards,
Mike
Mike
-
rjlittlefield
- Site Admin
- Posts: 23606
- Joined: Tue Aug 01, 2006 8:34 am
- Location: Richland, Washington State, USA
- Contact:
The "160" designation implies finite.
The relationship between "160" and 150 is because almost all finite objectives are designed to form their image 10 mm down from the top of the eyepiece tube. Hence a tube length of "160" corresponds to 160-10=150 mm from objective to image.
Some finite objectives are designed for tube lengths other than 160. For example some Nikon metallurgical objectives are designated "210/0". That means 210 mm tube length with no cover glass, and the 210 mm tube corresponds to 210-10=200 mm from objective to image.
A few older objectives were designed to form their images more than 10 mm inside the tube. I vaguely recall 170 mm tube length and 18 mm inside the tube, so 152 mm from objective to image. But those objectives are not likely to work well when just stuck in front of a camera, because they were designed to expect some aberration corrections to be done in the eyepiece.
--Rik
The relationship between "160" and 150 is because almost all finite objectives are designed to form their image 10 mm down from the top of the eyepiece tube. Hence a tube length of "160" corresponds to 160-10=150 mm from objective to image.
Some finite objectives are designed for tube lengths other than 160. For example some Nikon metallurgical objectives are designated "210/0". That means 210 mm tube length with no cover glass, and the 210 mm tube corresponds to 210-10=200 mm from objective to image.
A few older objectives were designed to form their images more than 10 mm inside the tube. I vaguely recall 170 mm tube length and 18 mm inside the tube, so 152 mm from objective to image. But those objectives are not likely to work well when just stuck in front of a camera, because they were designed to expect some aberration corrections to be done in the eyepiece.
--Rik
