Another cult lens

[ferider]

How do you calculate nominal focal length? I'd like to try with my Zuiko glass!

This is what I did, BT:

I measured the length of the lens at various focus scale settings. I used the infinity measurement to offset the other measurements. Then I predicted focus error using

1/Id + 1/Od = 1/f

where Id is the image distance, Od the object distance (lens focus scale), and f the focal length.

I am interested in getting more details of how you attached the tube Roland. If it is a part that you can easily make I would love to get one from you if you decide to make them available even if they will need slight adjustment by the end user. I have one of those Pentax lenses as well and I always thought it would be ideal to convert it being as small as it is.

Patrick, I debated if I should solder or glue. In the end I used an Epoxy based glue after roughing up the surfaces. Feels very strong. If you don't mind doing the end adjustment (filing down the last mm or so of the cam to fit to your camera), I'd be willing to do another one - still have some pipe. But I would need your lens and adapter for a couple of weeks. And for the lens, this is not reversible, the adapter remains untouched. Still have some brass pipe. Send me a PM if you really want to do this.

Cheers,

Roland.

 

[ferider]

Cool, but not practical. Cool anyway.

If anybody wonders about handling:

Without hood, and with filter, the lens intrudes just a little in the VF; about half way between 75 and 50mm frame-line corners of my M4P. The lens seems quite flare resistant. The assembly is sturdy, the lens locks to the adapter, and then can be mounted and unmounted like any other M lens. The Novoflex adapter is expensive but built very well (as the moon photo above also shows); it brings up 50mm frame-lines. Full aperture stops between f1.4 and 2, and f16 and f22, respectively. Half stops between f2 and f16. Focus is against the normal Leica direction, with 90 degrees throw from infinity to 1m. On the above M4P focus coupling goes down to about 0.65m.

Roland.

 

[splitimageview]

It looks like it is well balanced. Excellent conversion!

 

[ampguy]

Roland, Roland, Roland - I gotta get you an Arduino starter kit like I am for my son 😉

 

[ferider]

How about a Lathe instead, Ted 🙂

 

[filmtwit]

Have you been able to make a rear cap for this as of yet?

 

[ferider]

It takes a normal M cap. See post #62.

 

[ferider]

VF intrusion

VF intrusion

Now with hood, sorry for the cr*ppy iPhone pic:

 

[ferider]

In actual use

In actual use

Nothing spectacular, some season-appropriate snaps on Tmax 400 in Rodinal 1:100:

When I am thinking about another lens with similar rendering, the closest that comes to mind is my 75/1.4 ....

Cheers,

Roland.

 

[raid]

Roland,
Would you do such a conversion for a fair compensation?

 

[Godfrey]

That's a very inventive and neat conversion! Bravo! You have a quite unique lens for your M... 🙂

 

[ferider]

Roland,
Would you do such a conversion for a fair compensation?

I don't do this kind of work for money, Raid. But if you send me lens and adapter, I can do another conversion for shipping costs only - provided the lens doesn't end up for sale for more than it cost originally a couple of months later.

Cheers,

Roland.

 

[raid]

This is vey much appreciated. I just wanted to be fair.
I hope that I have not insulted or annoyed you, Roland.

 

[ferider]

Not at all, Raid.

 

[raid]

I will need to find the suitable adapter first.

Thanks.

 

[raid]

There are many different Pentax Leica adapters for sale. Is this one OK, for example:
http://www.ebay.com/itm/METAL-PENTA...373?pt=LH_DefaultDomain_0&hash=item256ac10c05


.... or this one:

http://www.ebay.com/itm/Leica-M39-l...498?pt=LH_DefaultDomain_0&hash=item2ea1f3fd5a


.... or this one:


http://www.ebay.com/itm/NEW-ADAPTER...865?pt=LH_DefaultDomain_0&hash=item5d318d4701

 

[Benjamin Marks]

Lovely images. I would like to see more, even though I don't think this sort of lens conversion is in my future.

 

[sanmich]

Roland

That's a beautiful conversion. I'm impressed...
To have a 1.4 50mm coupled to 0.7m at a sub-stratospheric price is GREAT.🙂

Just to be sure: the requirement to have the exact 51.6mm FL is because the cam is flat, right?
I mean, with very precise machining and calculations, and given the ability to adapt the cam, you could adapt any lens and correct its movement through a gain in the can (?)

Another question, please: How is this Pentax in terms of distortion?
I gave up my canon ltm 1.4 which is otherwise a brilliant lens because of distortion and minimum focusing distance, and since then, find myself drooling on fast glass with no ability to justify the price of it...

 

[ferider]

Roland

That's a beautiful conversion. I'm impressed...
To have a 1.4 50mm coupled to 0.7m at a sub-stratospheric price is GREAT.🙂

Just to be sure: the requirement to have the exact 51.6mm FL is because the cam is flat, right?
I mean, with very precise machining and calculations, and given the ability to adapt the cam, you could adapt any lens and correct its movement through a gain in the can (?)

Another question, please: How is this Pentax in terms of distortion?
I gave up my canon ltm 1.4 which is otherwise a brilliant lens because of distortion and minimum focusing distance, and since then, find myself drooling on fast glass with no ability to justify the price of it...

Thanks, Michael. The requirement of 51.6mm FL comes from the Leica RF calibration.

You could only use a slanted cam and correct for a different focal length, if the rear of the lens would rotate (which it doesn't for most SLR lenses). Otherwise you need a double helix.

The pictures above (uncorrected) show that the lens barrel distorts just a little. Much less than Canon 50/1.4 or Summilux v2.

Cheers,

Roland.

 

[ferider]

There are many different Pentax Leica adapters for sale. Is this one OK, for example:
http://www.ebay.com/itm/METAL-PENTA...373?pt=LH_DefaultDomain_0&hash=item256ac10c05


.... or this one:

http://www.ebay.com/itm/Leica-M39-l...498?pt=LH_DefaultDomain_0&hash=item2ea1f3fd5a


.... or this one:


http://www.ebay.com/itm/NEW-ADAPTER...865?pt=LH_DefaultDomain_0&hash=item5d318d4701

The last one might work, Raid. Would be interesting to try. Not sure how the rear of an M42 lens looks like. The others are a no-go.

My Novoflex adapter converts Pentak bayonett to M. There is a cheaper one available on ebay, like this: http://www.ebay.com/itm/250916389253

Roland.