M42 lenses on A6000 focus problem

[dogstar]

Dear fellows

 

Today I tried an old m42 lens 300mm on my A6000.

I have 2 adapter for this: one short really slim and another one quite thick.

I didn't manage to reach the focus. It's out of the range with both. Neither with a subject at infinity.

Did anybody tried? 

Some idea why?

It's so strange.

I used with the same lens a canon 6d FF and worked great.

[dogstar]

any suggestions?

[Username]

any suggestions?

    

I suspect the adapters aren't normal M42 adapters. 

   

Even a poorly toleranced adapter will ALMOST get 

infinity focus. The longer the FL, the less any small 

flange distance errors will mean. So with a 300 that 

doesn't quite reach inf focus a 20mm lens would be 

unable to focus beyond a few feet. A gross error at 

300mm is NOT due to an out-of-tolerance adapter.  

    

Do you measure approx 45mm from the front face 

of the adapter from the focal plane of the body ? If 

so, I wonder if the stop-down flange in the adapter 

is the problem. If the iris actuator pin on the lens is 

jammed, such a flange [that is normally beneficial 

and necessary] could block the lens from seating 

to full depth in the adapter. 

   

https://en.wikipedia.org/wiki/Flange_focal_distance   

   

BTW, does one of the adapters have glass in it ? If 

so, it may be calibrated for wide-to-normal FL, and 

lengthens the effective FL of the 300 way too much.   

   

Other long shot possibility is you've found a 42x0.75 

adapter for E-mount. Not only will it have too short a 

flange distance, but an M42 lens will only thread into 

it a few turns before it binds up. This would explain 

the adapter you say is rather short.   

  

I'm rather curious how you acquired these. The M42 

adapters on the market are overwhelmingly normal 

ones. To bag TWO odd ducks is kinda unthinkable ?   

   

Not sure if it's even possible but maybe the reverse 

of the above is going on. If the 300mm is a camera

maker's brand, then this last thought does not apply: 

   

I'm wondering if you do not have an M42 lens in the 

first place. IOW you put a T-mount [aka T2] lens on 

the Canon via a normal T2 adapter [42x0.75 thread] 

and now you're jamming the lens's T2 thread into a 

couple of [normal] M42-to-Canon adapters. Flange 

depth for a T2 lens [without installing a T2 mount or 

adapter] is 55mm. So ...... 

  

If the adapter that puts that 300mm onto your Canon 

body is about 11mm thick, you DO have a 300mm T2 

lens. Any normal M42 to Canon adapter is only about

1.5mm thick.   

 

If the adapter for the Canon is about 11mm deep then

nothing is out of tolerance, but you do have incorrect

hardware. If the "M42-to-Canon" adapters are normal,

then you just need a T2 mount for the rear of the T2

lens. Alternatively, you'd leave the Canon adapter on

the 300mm and just get a "dumb" adapter for Canon

lenses to Sony E-mount bodies. Someone may try to 

"upgrade" you to a "smart " adapter. It's useful if you 

wanna use real Canon EF lenses on the Sony, but is 

of zero benefit with M42 and/or T2 lenses, cuz those 

have no electronics in them.  

      

Below, the thin adapter is M42 to Canon. The thick 

one is a T2 mount adapters for T2 onto Canon.

    

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[Guest Jaf-Photo]

Guessing here. It sounds like one adapter is a M42 to Canon adapter and the second is a Canon to Sony adapter.That would mean you don't get the correct distance between the sensor and the lens. If that is the case, it will work if you just buy one M42 to Sony adapter instead.

 

If there is a T2 adapter involved, I don't know because I avoid those.

 

Dear fellows

 

Today I tried an old m42 lens 300mm on my A6000.

I have 2 adapter for this: one short really slim and another one quite thick.

I didn't manage to reach the focus. It's out of the range with both. Neither with a subject at infinity.

Did anybody tried?

Some idea why?

It's so strange.

I used with the same lens a canon 6d FF and worked great.

[dogstar]

Dear

you are so kind to reply me so deeply!

I take time to study all the things you wrote me. First I can already say that there is no glass in the adaptator, they are chinese rings just metal really simply and one is short and the other is the standard height for the nex e mount. Np problem for the thread becaus it screws and that's all, so no worry about T2\m42x1 or x2 questions. It is a matter of focal millimeters.

I'll come to you with the mesures!

[dogstar]

Ok so

 

Here I 'm with the corect mesures:

With the short M42 I have 38mm from the last lens in the back of the tele 300.

With the long M42 I have 78mm from the last lens in the back of the tele 300.

With both I cannot reach focus. Doesn't matter the size fo the screw (m42x1 or x2) it fits till the end with both.

 

 

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[Username]

`    

    

Measurement to a piece of glass has no meaning. 

  

The flange faces are the flat circular surfaces that 

meet when a lens is mounted. One flange is is on 

the lens, the other is on the body. When reporting 

a "flange distance" you don't even need to have a 

lens on hand. 

   

The flange distance for M42 is about 44mm and

you must measure this from the flange face on the 

M42 mount [at the front of the adapter] to the focal 

plane [same as sensor location plane]. The focal 

plane is marked on the body by a circle with a line 

crossing through it. It's a very small symbol and is 

on the top cover of the camera. 

   

I cannot read the notes on your papers. The photo 

is very unclear. 

[michelb]

This is what a M42 to NEX (E-mount) should look like from the side

 

Anything longer or shorter is likely to disallow focus at some distances

 

[dogstar]

yes its the same that I have. Simply identical

Moreover this m42 ring works with other lenses!

Ok so the mesures of the two M42 rings are:

42mm for the big (the above photo)

5mm for the short one

[dogstar]

Also I discovers that the last part can be unscrewed

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[Username]

`   

   

   

I won't repeat all I wrote in post number 3, but that

is where the answer exists. 

   

Referring back to post #3, I warned you about the 

existence of 2 different 42mm threads, the T-2 and 

the M42. The lens with the removable end is a T-2 

lens. Look up [Google] "T-mount photo lens". Try 

Wikipedia in particular.  

   

You say that all your 42mm threads thread nicely 

and do not bind up before seating fully. Normally if 

you mix a T-2 with an M42 it's typical to get a poor

fit that won't thread all the way in. But with sloppy 

manufacturing tolerances combined with soft metal 

such as aluminum, occasionally a mismatch WILL 

thread all the way together. I suspect that is what 

you are encountering. 

   

You seem to have at least one T-2 lens. You also

have an M42 adapter. What you've called "screw

unknown" is an assembly connection not intended 

for routine removal. It does allow for removing, or 

reversing, of the tripod collar, which is supposed  

to be included with such lenses. What you labeled  

"M42 short" looks like an M42 T-2 mount wearing

an M42 to Canon adapter. 

 

For any further info, go back to Post #3. Be sure

you do not confuse your removable M42 mount

for the T-2 lens with any other M42 devices, such 

as adapters for M42 lenses onto Sony or Canon. 

   

If you haven't yet read this, read it:  

https://en.wikipedia.org/wiki/Flange_focal_distance#cite_note-ikegami.com-2      

 I have not checked it for errors, but overall it will 

give you understanding of flange distance. 

[Username]

yes its the same that I have. Simply identical

Moreover this m42 ring works with other lenses!

Ok so the mesures of the two M42 rings are:

42mm for the big (the above photo)

5mm for the short one

   

Flange face to flange face, any Sony to M42

adapter must measure 27.46mm in length. 

 

If you are measuring the front flange face to

focal plane distance of an M42 adapter when 

installed on a Sony, that should be 45.46mm. 

   

Did this M42 telephoto lens focus properly 

when adapted to a Canon ? 

[dogstar]

yes on canon works. On canon 6D

[Username]

yes on canon works. On canon 6D

OK so on a proper adapter it will 

focus properly on the Sony. Use 

your adapter that is 27.46mm in

length. If none of your adapters 

is that spec, get one that is. 

[dogstar]

yes on canon worked. on 6D was ok

[dogstar]

ok anyway for sony aps-c it HAS to be 27.46mm right?

for sony FF more right?

[Guest Jaf-Photo]

This thread is moving in circles. I would suggest a quick online search for "flange distance Sony". That will throw up multiple sources that answer all questions.

[michelb]

ok anyway for sony aps-c it HAS to be 27.46mm right?

for sony FF more right?

 

No they should be exactly the same for FF as for APS-C