Minolta Micro Bellows Lens 12,5mm

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Caponito
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Minolta Micro Bellows Lens 12,5mm

Post by Caponito »

Dear Members,

I am starting to go more away from 1:1 or 3:1... yesterday I buy a Minolta Micro Bellows lens 12,5mm, reading some reviews, find that it is possible to go at 20:1 max.

Somebody can tell me your experience, or maybe tell me more about the lens?

Best Regards.

PS: Sorry, my english is so bad. :oops:

Eric F
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Joined: Tue Nov 11, 2008 1:38 pm
Location: Sacramento, Calif.

Post by Eric F »

Hi Caponito,

Welcome to Photomacrography! (And: your English is great, though no problem if it wasn't...)

Congratulations on getting the little Minolta 12.5 lens. I have one, and I find it to be very sharp. I use it only in the lab, on a stand; the working distance is quite short (5 - 8mm) but the tip of the lens is tapered, so you can get enough light on your subject. I find mine is best at f/2.8. I think you'll like this lens a lot!

Cheers,

Eric

Dave_Anderson
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Joined: Sun Jul 17, 2011 12:26 am
Location: Sunnyvale, Ca.

Post by Dave_Anderson »

Welcome! I purchased one not long ago and have little experience with it but so far it looks very promising. I have sent many of my adapters off to my brother for some modifications(I want to mount a ringflash to my Minolta M1 & M2 adapters) so it's going to be a while before I can do much, but with the M1 adapter alone I was getting 5.7x magnification and with fully extended bellows and the M2 adapter it was looking like ~27.5x. Note, the M2 adapter puts the base of the RMS mount about 1/2" extended from the mount flange on the body. I have a way to get it flush with the flange but that's an experiment for another day.

Eric, do you get a lot of diffraction when you stop down? Or is the longer flash duration when stopped down a problem?

ChrisR
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Post by ChrisR »

Diffraction will be significant for you using this lens. If you use higher magnifications or shut the lens down, it will be more.
Search the forum, and have a look here:
http://www.cambridgeincolour.com/tutori ... graphy.htm

Remember the Effective Aperture is the marked "f" number multiplied by magnification +1.
( The pupillary magnification factor also comes in to the equation).
So if PMF is 1, and you use marked f/2.5 at , for example 8x, your effective aperture will be
2.5 x (8+1) = f/22.5
Depending on the size of the pixels in your sensor, that magnification may be about where you notice the sharpness is "killed". Higher magnification eventually becomes "empty" so the image is bigger but there's no more detail.

Microscope objectives from about 10x have much wider apertures, for this reason.

Dave_Anderson
Posts: 17
Joined: Sun Jul 17, 2011 12:26 am
Location: Sunnyvale, Ca.

Post by Dave_Anderson »

Thanks for the info Chris. I'm just going to have to experiment to see how things work out. I have a 24x36 sensor with 5.9µ pixel pitch so diffraction calcs ought to be adjusted about 1 stop. When I was looking through the vf it looked pretty sharp on the steel scale I was looking at, but I did not have the lighting set up for any captures. I'll be posting results when I have them.

Caponito
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Joined: Mon Aug 15, 2011 4:15 pm
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Post by Caponito »

Thank's to all!

Unfortunatelly I dont have the M1 o M2 adapters, only a simple M42 to RMS, I wish to use the lens mounted on a Pentax Auto Bellows II, I make some modifications to mount a Twin and a Ring flash on the front of the bellows.

when the lens arrives I'll do some tests

Best Regads
Last edited by Caponito on Mon Aug 29, 2011 4:43 pm, edited 1 time in total.

Charles Krebs
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Location: Issaquah, WA USA
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Post by Charles Krebs »

The 12.5/2 Minolta is a great little lens. Excellent quality. (Somewhat equivalent in use to a 10/0.25 microscope objective). But I would not try "pushing" it up to 20X... since with an f/2 maximum aperture you will have significant diffraction losses. For 20X you will get much better resolution with a 20/0.40 microscope objective.

I have posted a few shots taken with the 12.5 Minolta on the forums. If you are curious they can be seen here:

http://www.photomacrography.net/forum/v ... .php?t=263
http://www.photomacrography.net/forum/v ... php?t=2557
http://www.photomacrography.net/forum/v ... php?t=3265
http://www.photomacrography.net/forum/v ... php?t=4711
http://www.photomacrography1.net/forum/ ... php?t=2059

Dave_Anderson
Posts: 17
Joined: Sun Jul 17, 2011 12:26 am
Location: Sunnyvale, Ca.

Post by Dave_Anderson »

Thank you for weighing in, Charles. What was the magnification on the yellowjacket mandibles and on the harvestman? I would be very pleased to get such detailed pictures from my 12.5.

A quick perusal of ebay turned up a Nikon CF Plan 20x .40... with a $1290 BIN! I think I'm just going to find the limitations of the Minolta lens with my setup and live within them for the time being. :) I do have an eye out for cheap LWD/metallurgical objectives, but that's a very low priority at the moment.

Caponito
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Joined: Mon Aug 15, 2011 4:15 pm
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Post by Caponito »

Charles,

Many thanks for the info, I would like to know what is the max ratio that the Minolta 12.5 lens can offer in order to an acceptable image?

I always use common macro lens, I am a Minolta/Sony user, I have 50mm, 100mm, 3X-1X and a Zeiss 8x30 monocular & +8Dptr.

All the sample pictures with the Minolta 12.5 are very cool.

Thanks again.

Regards

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