Any experience using 50x/0.6 lens with Stackshot rail?

[cjjthomp]

I'm currently using a 10x/0.25 and a 20x/0.40, would like to use a 50x/0.6 but I'm concerned that the Stackshot may have trouble with the spacing. I could get 1.5 micron spacing by using "steps" (one step = 0.5 microns) instead of microns, but is it likely to produce "stick-slip" effects? Magnification would commonly be 25x using the Canon 100mm macro as a tube lens, or occasionally as high as 50x with the 70-200mm zoom lens as a tube. The setup is very solid and I use electronic flash lighting, so I don't expect vibration to be a problem.

Thanks in advance,

Jeff Thompson

[rjlittlefield]

StackShot at NA 0.6 would be marginal. It might work, might not, depending on the condition of your particular unit. At best, due to variation in actual step size you'll have to use a nominal step size that is significantly less than 1.5 microns, in order to limit the actual maximum step size to that value.

For some discussion of the issues, see http://www.photomacrography.net/forum/v ... hp?t=16323 . Here's a particularly relevant part:

With High Precision ON, that pattern is not completely suppressed, but it's cut way down. In this run, the largest single microstep is 1.38 microns versus 0.496 microns average, and the largest double microstep is 2.06 microns versus 0.992 microns average.

So, for high magnification work such as 40X or 50X, what I do is to set a nominal step size of 1 micron (2 microsteps), knowing this means that most of the time I'll get a little less than 1 micron and once in a while I'll get a hair over 2 microns. This is sufficient to avoid focus banding while still getting good rendition as illustrated at http://www.photomacrography.net/forum/v ... 997#103997.

If you're going to be working regularly with high mag, high NA, then a better approach is to repurpose a microscope focus block. Using that approach, it's very simple to reliably get step sizes as small as you need. Quoting from http://www.photomacrography.net/forum/v ... hp?t=11519,

This is a sequence of 132 moves, the largest of which measures a bit under 0.14 microns (average 0.0625 microns).

--Rik

[mawyatt]

Jeff,

Another option is to get a surplus THK KR15 or 20 rail off eBay with 1mm pitch and use it with the Stackshot Controller.

Best,

Mike

[cjjthomp]

"So, for high magnification work such as 40X or 50X, what I do is to set a nominal step size of 1 micron (2 microsteps), knowing this means that most of the time I'll get a little less than 1 micron and once in a while I'll get a hair over 2 microns. This is sufficient to avoid focus banding..."

I think this is what I'll try first - it doesn't involve any new equipment and it sounds like it will work OK.
Thanks for the input,

jeff