Rigidly mounting an odd combination: T2i + 85L f/1.2

[ChadS]

@DrC thanks for the suggestions. Believe it or not the 85 does stick out below the bottom of a T2i! However, for my purposes the T2i's frame is nowhere near rigid enough even if I could bolt it down sufficiently. I need to have less than 1 pixel's displacement over a series of 1000 captures or so. The trouble is the mirror slap. I know how to lock it up and then shoot a picture but I'd love to leave it up and locked out of the way. Anyways, 1 pixel of motion is about 40 micron at 3 feet away (gotta love mixed units - at a meter away) which is about 8 arcseconds of displacement. The Manfrotto support you listed is for-sale on Amazon for ~$70 and is similar enough to what I'd have built that I'll save myself the time. Tha

[HDNitehawk]

@ChadS my thought is, do you really have to use the 85mm F/1.2 when there are other primes that already have the tripod foot mounted.

My second thought is, 1 pixel displacement over 1000 captures, no way any of the methods you mentioned will be that rigid. You will need a system that you can recalibrate your alignment occasionally, if not very frequently. That is provided the mechanical parts inside of the lens and camera can be held to that tight of a tolerance, which I have my doubts they can.

One problem I see is that the 85mm is not made to mount a clamp in the manner you are talking about. A mount this stable would be similar to a mount on a rifle scope, a rifle scope is made to take a clamp that puts out an extreme amount of pressure. The barrel of the 85mm may or may not be made to take this pressure. You very well may damage your lens. If a clamp is the way you go, you should be looking for something that will fit around the barrel fully, otherwise you risk egging the barrel of the lens. Just the temperature difference of the non similar metals and components will make it very difficult to keep it consistent.


Good Luck with your Experiment.

[ChadS]

@HD welcome to my world! The 85 was chosen according to a long list of criteria. I wanted to use the macro 180 but it isn't as fast at the working distances we're starting at (though we may return to 1:1 within the next few months). We considered 25 lenses from Zeiss, Canon, and Tamron and ended up with the 85 as the best choice. The 200 was close but the field of view was simply not close enough to the final project to buy and the f/# is nowhere near as fast (shallow DoF is critical to the project).

A rifle scope is designed to hard-mount to a barrel and not translate during a high-g acceleration (the bullet shot). I don't have to be so aggressive. I can let the lens breathe and flex so long as it returns on-target after the motion. I've had success in the past making my own mounts for "things" that are as repeatable as I've mentioned but I've never used commercial lens systems before (usually things like long-distance microscopes or bare lenses) so this will be a learning experience for me.

[HDNitehawk]

ChadS, if shallow DOF is a key point wouldn't the 180mm L give you a smaller depth of field at its minimum focus distance of 1' 6" @F3.5 than the 85mm gives you at its minimum focus distance of 3.2' at F1.2. Or how about either the 100mm macro or 100mm macro L which gives you 1' distance. Perhaps they are not giving you the framing you want, and then you could go with a FF camera which actually would even give you a tight DOF. Any of those lenses would have tripod feet available.

Of course I do not know what you are trying to do, I am just throwing out things that you may have already considered (or not)

[ChadS]

@HD You're exactly correct. DoF goes as the 1 / magnification squared (basically). so at macro distances the DoF would be insanely thin - and we will repeat this entire project with just such a lens once we've got everything else working. However, for now the customer wants a substantially larger interrogation region than could be imaged at 1:1. Instead, the 0.1x mag of the 85mm lens works out almost perfectly. Were I to use the 180 at the same framing the DoF would be substantially thicker.

DoF is not my only issue. If I just needed thin DoF I'd use a 1000x microscope objective. And while cool, those beasties don't allow for much field of view. Thanks for the help though, fresh eyes are always appreciated.

[neuroanatomist]

If I just needed thin DoF I'd use a 1000x microscope objective.

Wow - where'd you get one of those? My highest power objectives for routine use are 100x NA=1.4 and require oil immersion, although I do have a 150x NA=1.35 glycerol immersion lens, and a 150x NA=0.95 dry lens for materials work.

[ChadS]

@John with what occular? Magnify the magnified image man! Okay so I did say objective and not system mag. Seriously though I was just exaggerating my point. Leave it to the bio guy to catch me. :P

edit: sorry if I got you all excited for a moment... I don't do micro work. All my stuff is macro (a few microns on a side at least).

[HDNitehawk]

Wow - where'd you get one of those? My highest power objectives for routine use are 100x NA=1.4 and require oil immersion, although I do have a 150x NA=1.35 glycerol immersion lens, and a 150x NA=0.95 dry lens for materials work.

Where can I get these and...do they have an adapter so I can hook it up to my 5D II

[ChadS]

Where can I get these and...do they have an adapter so I can hook it up to my 5D II

http://www.edmundoptics.com/products...categoryid=172
Edmund is sort of like the Walmart or Target of optical supplies. They have everything but not necessarily the high-end stuff. There are 100x objectives for Mitutoyo infinity-corrected objectives and several in the finites.

As to mounting your 5dII? Most microscopes these days have some sort of camera port that you can use instead of an eyepiece. Think your current lenses are expensive? Check out the prices of the good objectives - $21k for an 80X UV objective and that's for something that weighs about a pound.

[dsiegel5151]

This company sells pretty cheap adaptors for an EF mount camera to a microscope:

http://www.martinmicroscope.com/

Really nice guys too. I mostly keep my T3i on my microscope, but I also have taken nice images with my 5D and 20D. In terms of price for good objectives, ChadS is right. They are not cheap. My Olympus phase contrast objectives were roughly $5000 a piece. Thus, I paid around $20,000 (well, the university paid) for 4x, 10x, 20x, and and 40x phase contrast objectives

Male Red-spotted Newt cloaca at 40x total magnification. Canon T3i, Olympus BX40 microscope.