Mitutoyo QV objectives

[Blame]

I am building up the parts for my own photomicrography project.

So far I have:

Canon 50D
Sigma 150mm macro
mitutoyo QV 2.5X and 5X Objectives

My plan is to bolt an Objective onto the end of the sigma macro.

If I am right the QV's are standard 5X and 10X apo's with a spacer screwed onto the back end. They have the same N.A (0.14 & 0.28), the same working distance (33.5mm & 34mm), and apart for an empty spacer bolted on the back, the same dimensions. The magnifications are quoted when used with a 100mm rather than 200mm tube lens so magnifications are effectivly identical too.

But am I right? I phoned the expert at mitutoyo UK and he said no. He stated that they are will only work with QV microscopes. He was rather forceful.

Hm. I wonder. Only Mitutoyo sell QV objectives, but just about everybody sells objectives compatable with Mitutoyo's standard range. Have I stumbled on something mitutoyo doesn't want known?


Anyway, can anybody give me more info on the QV series?

Before anyone digs in, I know 150mm is a bit short for my tube lens, but Mitutoyo objectives (at least non-QV) have a 30mm field of view with 200mm so I should get 22.5mm. The corners of the 15.5X22.5 camera sensor won't be perfect but I will at least get more of the usable field in frame in the vertical direction. It should work out a little under f14 with ether objective, and magnifications of 3.75X and 7.5X.

To tell the truth I was nervous of squeezing to the corners for fear of the camera lens letting me down. Silly me. The Sigma was perfect corner to corner (although thank god I chose a camera with adjustment for front focusing).

Oh, while I am asking, anybody know an easy way to bolt a mitutoyo objective (26mm 36tpi I think) onto a 72mm camera filter thread?

Thanks.

[Cyclops]

How are you attaching the objective onto the macro lens? Do you use a lens cap with a hole drilled in the centre, glueig the objective in place? If this is workable I'd like to try this with my 100mm macro lens! I have some microscope objectives (4,10, 20 and 40X) but the microsocpe is falling apart so dont really use it now.
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Canon 30D | EOS Rebel 2000-film(aka EOS 300) | Panasonic FZ-7 EB | Vivitar/Cosina 100mm f3.5 macro lens | EF 75-300 f4.5-5.6 USM III | EF 50 f1.8 II | Vivitar Series 1 19-35 f3.5-4.5 | Slik 88 Tripod. | My new blog:
http://mybackyardsafari.blogspot.com/

[RogelioMoreno]

To attaching an objective onto a lens you will need:

1. A set of step down ring:

http://www.amazon.com/Fotodiox-Anodized-77-72mm-72-67mm-67-62mm/dp/B001G45VTE/ref=sr_1_1?ie=UTF8&s=electronics&qid=1273941574&sr=8-1


2. A 52mm to M42 step down ring:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180458863544&ssPageName=STRK:MEBDIX:IT

3. A M42 to RMS adapter (this adapter allows you mount only objectives with RMS thread):

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350352400700

or

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200470968028

4. For objectives with 26mm thread, a 26mm to RMS adapter:

http://cgi.ebay.com/1-internal-and-RMS-external-Threads-adapter-1A4-/370321401850?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item5638e027fa

Rogelio

[Cyclops]

Quite a lot of outlay there! Be cheaper, and easier, to buy a true macro lens after all the $$$!
_________________
Canon 30D | EOS Rebel 2000-film(aka EOS 300) | Panasonic FZ-7 EB | Vivitar/Cosina 100mm f3.5 macro lens | EF 75-300 f4.5-5.6 USM III | EF 50 f1.8 II | Vivitar Series 1 19-35 f3.5-4.5 | Slik 88 Tripod. | My new blog:
http://mybackyardsafari.blogspot.com/

[Blame]

Hi Cyclops.

Yes, Quite a lot of money, but there was a method in my madness.

The Sigma 150mm cost 380 pounds, but I am far from regretting it. It is tripple purpose. Macro, Shortish telephoto and tube lens. Initial tests on the image quality are superb.

I am not sure how much I paid for the Canon 50D. I sold its lens on another camera. All I can say is that if you want the quality and value of Sigma lenses you had better not be stuck with a camera that has no adjustment for front/back focusing.

The bargain was the 2 Mitutoyo. I bid 100 pounds delivered to no opposition. Nobody knew what they were, and I'm still not sure, but I am hopeful. So at this point at least, my outlay is just 100 pounds. The rest of the equipment is just my normal camera kit.

But what do you mean by a true macro? The only non do-it-yourself kit I know about for above 1X is the Canon MP-E 65mm.

Anyway. I wanted the best I could afford, and like other posters I watched a Nikon apo 4X 0.2 NA 160/- go for about 1000 dollars with despair.

The Mitutoyo lenses have a lower NA for their magnification (In the range from 1X to about 20X you can hope for resolution to be proportional to magnification), but it could be that this is compensated, at least in part, by a larger field of view. A simple (and posibly accurate) formula for picture quality would be: NA X Field of view / Magnification.

Sadly while NA and magnification are easily quantified, field of view is a wooly figure. Where exactly does the image quality deteriorate to the point that the field of view may be stretched no further? A good topic for discussion all on its own. My own research on the net sugests that the Mitutoyo have an edge here, and posibly a substantual one.

Anyway, there is one other reason to go for the Mitutoyo lenses. They have incredible working distances. 34mm in this context is huge. It is not just a matter of accidentely sqashing your carefully mounted beetle, or finding space to get the light in. There is also the tricky matter of stacking photos. A long working distance implies a long focul length. That results in less perspective changes when you move the lens (or subject) for each shot in the stack. That results in easier interpretation for the stacking software and thus fewer anomolies.

My maths tells me that in theory this setup should rival the picure quality of a decentish camera lens at f14. To a not too critical eye, perfect. There is a wide gap between theory and practice, but it has to be worth a try.

[Blame]

Hi RogelioMoreno.

Thank you for those links. A stack of no less than 4 adapters! I fear that you are right, but it seams a bit heath-robertson. In particular I am worried about the RMS adapter. I would have to do some careful maths to convince myself that it won't cause vignetting.

I would prefer to go for a simple 72mm diameter disk with 26mm central hole, but we shall see.

[Blame]

Cyclops.

I am not sure the combination of typical microscope lenses and a 100mm macro will work too well.

The field of view of typical infinite plan objectives are quoted at about 25mm. Less if not plan. However it is a rare microscope occular that gets even close. 18mm is common. Camera setups are even more conservative. Typical diagonals are about 16mm. That does suggest that the circle of quality is rather smaller.

Asuming that your objective was designed for a tube lenth of 200mm, and you are using a canon cropped frame camera with a sensor of 22.5mm width, the good quality circle would have a diameter of something like 5/9 to 1/3 of the picture width.

That is not neccesarily the end of your problems. I am using objectives that (I believe) require a simple tube lens. Some otherwise superb objective need a compensating tube lens.

You need something closer to a 200mm lens. I am using 150mm, but the mitutoyo has an exceptionaly wide field of view, and I am still expecting to loose the corners.

[Cyclops]

[Blame]

Back focusing & front focusing is just about how it sounds. The auto-focus is off.

I tried taking pictures of trees only to get a blur for the trees with some increadably well focused grass in the foreground. Any lens (or camera) can have this problem but Sigma lenses are notorious for it.

Easily fixed with the better cameras as they are adjustable.

[DaveW]

Front or back focusing is simply the light path of the lens to the sensor having a different length to either that of the autofocus sensor or focusing screen, all of which should be adjustable by a camera repairer or the makers?

If the autofocus light path varies the autofocus sensor will focus the lens so it is in focus on it's sensor, but not on the camera sensor. Similarly if the lens to focusing screen light path varies when you manual focus using the focusing screen the lens will be in focus on the focusing screen but not on the sensor.

There are adjustments in the camera to bring all three light paths to equal length, and hence equally in focus for all three. Some of the latest cameras also allow you to exactly tune each lens into precise focus on the camera and the cameras electronics remember that lens and adjust focus accordingly.

To test for front or back focus see:-

http://photo.net/learn/focustest/

Also all lenses and camera focusing settings have a manufacturers tolerance. This may be small, but in some cases may be significant. If you have a lens with a slight forward focus and put it on a camera with a slight back focus the two errors will cancel themselves out. Conversely if you happen to get a camera with a slight forward focus and a lens with a slight forward focus the two errors add and you will get a distinct forward focus. The same applies when a camera and lens are combined both with back focus tendencies, the back focus error will then be compounded.

I cannot find a piece I read by a photographic hire firm which said they often got lenses returned as focusing faulty, but they could not find anything the matter with them. When they gave the hirer another lens it worked OK. It was simply a case of the manufacturing focusing tolerance all makers allow in their equipment, probably noticeable more at full aperture when depth of field does not cover it up.

You often hear people on forums saying "they sent me three lenses before I got a good one". This may be true to a certain extent, but in many cases it is just a bad camera/lens lens focusing tolerance match. If you send your camera and lens to the manufacturers they can adjust them to each other. The problem then is if another lens worked well on the camera it may now be off focus if the camera was adjusted to the new lens.

I believe professional photographers often used to send all their camera bodies and lenses into the makers to be harmonised, but the advent of micro focus adjustment for individual lenses on new professional cameras has made this unnecessary, but in itself acknowledges that focus tolerance problems in photo equipment exists.

http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html

However as microfocus evidently only adjusts autofocus and you are not getting things in focus manually focusing on the focusing screen the camera may need a mirror adjustment by the repairers to harmonise the light paths.

DaveW

[Cyclops]

[Charles Krebs]

Blame,

I really have not found any good info on the QV Mitutoyos.

I realize you want to use your 150mm lens as a tube lens, but perhaps you might find something of interest in regards to tube lens placement here:

Page 26 of this pdf:
http://www.mitutoyo.com/pdf/E4191-378.pdf
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http://www.krebsmicro.com

[ChrisLilley]

[Blame]

Charles.

You have no idea how expensive Mitutoyo stuff is. I picked up the lenses cheap but there is just no way I can afford to buy the rest of the kit from mitutoyo brand new.

DaveW

I found an even easier method of checking the front focus than your link.

Just place some small object on the carpet. Or with my housekeeping just look for one. Then take a picture with auto focus centred on it from something like a 45 degree angle, and aparture wide open. What you will see in the picture is a horizontal line of defined carpet fibers surounded by blur. Just adjust the camera till the small object is smack in the centre of that line.

[rjlittlefield]

Since this discussion has drifted off into autofocus, there's a question I'd like to ask.

In my understanding -- which is apparently flawed -- autofocus works as a closed-loop system that adjusts the lens until the image is properly focused on the autofocus sensor.

I can easily understand that an adjustment might be required to bring the autofocus sensor perfectly in accordance with the image sensor.

But I do not understand how a closed-loop autofocus system can work OK with some lenses while fouling up with others. It seems like that would require some open-loop aspect of the system.

Can somebody explain to me what I've missed, or even better, point me to some reference that discusses it in detail?

Thanks!

--Rik