Tube sections shown in the photos are 7, 14, and 28 mm.dolmadis wrote:May I trouble you please to give me an indication of the length of M42 tubes back to the camera that I might need with an assembly for the DCR 250 and DCR150?
So for the DCR-250 you're looking at 28+28+7 = 63 mm, and for the DCR-150 it's the same plus 6*14 for a total of 147 mm.
The chain of three adapters to go from M42 (male) to 49mm (male) adds another 12 mm.
As a crosscheck... My DCR-150 and DCR-250 carry labels that specify distance from the shoulder of the outer male threads to the back of the camera mount adapter. Those distances were determined by mounting the lens on a bellows, focusing on something very far away, then measuring the setup. For the DCR-150, the label says "Infinity focus at 175.9 mm from male shoulder of reversed lens to flange of Canon camera". The lens body itself is about 15 mm thick, and the M42 adapter is about 1.5 mm (nominal 1.46), so as shown the DCR-150 setup would be a total of 1.5+147+12+15 = 175.5 mm. The fact that 175.9 and 175.5 are so close together is sheer luck and is quite unnecessary. In my latest tests working with the DCR-150 on D800E using a Mitutoyo M Plan Apo 10X NA 0.25 objective, one thing I did was to shorten the extension by close to 20 mm so as to match magnifications between the 10X + DCR-150 (on shortened extension) and the 10X + Mitutoyo MT-1 tube lens focused at infinity. Aside from making the image smaller, I didn't notice any significant change in image quality from the shortening. (Higher power objectives with larger NA would be more picky, however!)
As shown, yes, but I suspect it doesn't really matter. In my D800E tests, I has to use shorter separation between the objective and the DCR-150, to avoid vignetting caused by some baffling in my tubes. (Increased separation means that rays in the corner of the field strike the tube lens farther from the axis. From there they get bent to refocus on the sensor. So the greater the separation, the wider the clear space has to be, up close to the tube lens.)On the DCR150 is there another tube or tubes behind the cone?
--Rik