Topic: Minolta E Rokkor Enlarger Lens 50mm f4.5

[clagom]

Hi all, Not sure if this is the right area to post questions like this...

I managed to get a Minolta E Rokkor Enlarger Lens 50mm f4.5 for almost nothing. I intended to use it with my Leica Beoon instead of the Summarit 50mm. Today I got the lens, and I noticed that the diameter of the lens is smaller than the normal LTM one. I bought it because it said "M39 mount", so I thought it was right.
Do you know what kind of adapter I need in order to get it on the LTM mount?

This is the lens:


I googled a lot, but I couldn't find the right info, hence my question here...

Thank you!

[Francois]

I'm really surprised because most enlarger lenses are m39.
But I did see once one for a Meopta enlarger that was drastically smaller.
I don't know the exact dimensions and thread count but you might need to take a look at a c-mount adapter.
These are usually for cine cameras... Though they have also been used on security cameras.

[Bryan]

C mount is 1 inch (25.4mm), quite a bit smaller than LTM 39mm.  It could be an odd size but if it is C mount there are LTM adapters available.

[clagom]

I was surprised as well, I was sure it was a normal M39 enlarging lens :/
Indeed it seems roughly the size of a security camera lens. I played with C-mount lenses while ago, but at the moment I don't have any adapter to try. Also it seems there aren't many adapters from C to LTM or M mount.
Something like this might fit (even if the thread seems different):

I'll try to retrieve the size, not so much info around on this lens...

[clagom]

Sorry, never mind!
The small size of the lens confused me, but the size and the thread were right, it's a M39 lens. I didn't have the adapter with me and I thought it was small.

[Francois]

Just an optical illusion then.

I did check out the Meopta lenses to make sure I have the correct information, but yes they did use an odd lens mount on some of their enlargers.
Their Anaret 4.5/30, Anaret 4.5/50 and Belar 4.5/50 used the M 23.5 x 0.5 thread mount...

So if you should ever see one on an auction site, remember this.

I think this should be a public service announcement

[clagom]

You're right! There isn't much information around about these lenses...

Anyway, to continue with something useful, I tested the Rokkor to scan film with the Beoon. I always used the Summarit 50mm (the old f1,5 lens), so here's a comparison:

This is with the Summarit (f11 or f16):

The colours are a bit off, but here I'm comparing the sharpness and the contrast.

Here's the Minolta Rokkor (f22):

As you can see, with the Rokkor I cannot cover the whole sensor of the M9, while the Summarit actually cuts a bit of the photo, so it's closer than the 1:1

Another comparison about the sharpness on the corners:
Summarit, 100% crop:


Rokkor, 100% crop:


The Rokkor is sharper, but also because it's closer to the centre.

In the centre though, the Summarit appears sharper and more contrasty.

[Francois]

The enlargement sharpness simply comes down to the lens design and purpose.
The summarit is designed for regular photography while enlarger lenses are designed for reproducing documents and are what is called a flat field design. This is why it gives a sharper image.
On enlargers, for a bigger negative, you use a longer focal length.
On my enlargers, I use a 50mm roddenstock for 35mm film, an 80mm Nikkor (that replaced a 75mm kit lens) for 6x6 and a 135mm Schneider for 4x5 (the usual standard is 150)

[clagom]

Thanks for the info! This was also a reason why I bought this lens (for around 2£ I thought to try it out), but I didn't think it couldn't cover the whole sensor. It's not a huge problem, I kinda like the white margin around (it's the Beoon black mask inverted). Since these lenses are cheap though I think I may try some more Looking also for 6x9 film.

The enlargement sharpness simply comes down to the lens design and purpose.
The summarit is designed for regular photography while enlarger lenses are designed for reproducing documents and are what is called a flat field design. This is why it gives a sharper image.
On enlargers, for a bigger negative, you use a longer focal length.
On my enlargers, I use a 50mm roddenstock for 35mm film, an 80mm Nikkor (that replaced a 75mm kit lens) for 6x6 and a 135mm Schneider for 4x5 (the usual standard is 150)

[Francois]

I was looking at the pictures on a decent screen (not my cheap tablet) and can't see much of a problem with coverage.
The Rokkor covers the sensor well I think (bad sentence but anyways).