Bellows and microscope objectives

[gypsey]

When referring to the tube length 160/210 of a microscope objective used on a bellows, can someone tell me the location of the start and end points to achieve the correct tube length.

Thanks
gypsey

[AndrewC]

http://www.photomacrography.net/forum/v ... 160mm+tube

[gypsey]

Thanks for the link Andrew, but it doesn't answer my question unless one can read sensor instead of eyepiece when using bellows.

Regards
gypsey

[realjax]

>Thus an objective designed for a "160 mm tube" is actually designed for 150 mm from shoulder_above_the_mounting_threads to the sensor.

Doesn't this answer your question?

[Craig Gerard]

gypsey,

The 'end' point is the DSLR sensor or SLR film plane. The location of that varies and will depend upon the camera you are using.

The 'start' point... I need to have that clarified myself. I had assumed it was where the objective thread meets the objective barrel?

The bellows is used to 'fill in the gap' between the start and end points to provide the correct tube length/extension.
The bellows fittings (and any additonal extension, such as an RMS cone adapter) are also calculated into that 'gap' to arrive at the appropriate extension.

Once you have taken into account the matters listed above, you will find that that actual bellows extension is quite minimal.

/160 requires 150mm extension between objective 'shoulder' and sensor
/210 requires 200mm extension between objective 'shoulder' and sensor.

We need a diagram here


Craig

[gypsey]

Thanks to everyone, for all practical purposes I think the question has been answered, summed up by Craig, that when a microscope objective is used with a bellows, the optimum results will be obtained with a total measurement of 150/200 between the 'shoulder' and the sensor.

Regards
gypsey