Fits 7artisans 50mm F1.1 on Bessa R2M

[BossesBilder]

There is a lens named "7artisans 50mm F1.1" with Leica bayonet but it looks a bit deep, so I wanna know if anyone have tried this lens on Bessa R2M.

 

[mooge]

I don't have a R2M but it fits on my Bessa R2.

 

[hamish_gill]

There’s no reason it won’t fit on the r2m

 

[Dez]

I would be worried about focus accuracy of such a fast lens with the Bessas' short RF base.

Cheers
Dez

 

[splitimageview]

Only the R4 is a problem with 50/1.1

Here is a link to the RF accuracy chart

https://docs.google.com/spreadsheets/d/1BWB8ZaryAV8Q6UlBGFs6I5wwj-MdxeaSkLP_kiZVQgY

 

[Pioneer]

Only the R4 is a problem with 50/1.1

Here is a link to the RF accuracy chart

https://docs.google.com/spreadsheets/d/1BWB8ZaryAV8Q6UlBGFs6I5wwj-MdxeaSkLP_kiZVQgY

Wow.

Interesting chart. I would never have guessed that an M3 is that lousy at focusing lenses.

Of course I am almost certainly misunderstanding this.

 

[splitimageview]

Anything over 100% is iffy, anything under is good.

Click on the OK/NOT OK button for a quicker result

 

[Huss]

Only the R4 is a problem with 50/1.1

Here is a link to the RF accuracy chart

https://docs.google.com/spreadsheets/d/1BWB8ZaryAV8Q6UlBGFs6I5wwj-MdxeaSkLP_kiZVQgY

That chart shows errors for the MP
EBLs for the MP:

.58 39.7
.72 49.3
.85 + 1.2 magnifier 59.2
MP (.72?) + 1.5 magnifier 74

Problem is .85 + 1.2 magnifier, the result of 59.2 is incorrect. That would be the result of the .72 + 1.2 magnifier.

So, kinda discounting what I am seeing here. There's a whole lot of numbers, some which may or may not be correct, that results in a whole lot of nothing.

All that matters is :
1. That your camera's rf is correctly calibrated
and once that has been achieved
b. the EBL.

 

[Pioneer]

That chart shows errors for the MP
EBLs for the MP:

.58 39.7
.72 49.3
.85 + 1.2 magnifier 59.2
MP (.72?) + 1.5 magnifier 74

Problem is .85 + 1.2 magnifier, the result of 59.2 is incorrect. That would be the result of the .72 + 1.2 magnifier.

So, kinda discounting what I am seeing here. There's a whole lot of numbers, some which may or may not be correct, that results in a whole lot of nothing.

All that matters is :
1. That your camera's rf is correctly calibrated
and once that has been achieved
b. the EBL.

I read that as 0.85 viewfinder OR 1.2 magnifier on the standard 0.72 viewfinder, not plus.

Even the Go/No Go part is odd since the 135mm f/2.8 lens doesn't seem to be a GO with any camera on the list. I wonder why Leica built one then?

Could easily be wrong though since that is one of the few things I think I understand with this chart.

EDIT - I guess we are getting a bit off topic here since the issue is the 7Artisans lens, not this chart. 😀

 

[Huss]

I read that as 0.85 viewfinder OR 1.2 magnifier on the standard 0.72 viewfinder, not plus.

Down to it's simplest terms, a .72 viewfinder with a 1.2 magnifier has a magnification of .72 * 1.2 = .864. Which is more than .85. So for a chart w/ lots of numbers and stuff, that still is obviously wrong.

😉

But you're right, this is about the Bessa. The lens will fit, but accuracy really is down to rf alignment primarily, then everything else.

 

[splitimageview]

This RF accuracy chart was originally a spreadsheet created by Roland (ferider) in this thread.

If there are errors, please point them out and I'll update the sheet.

In the 9+ years this has been extant, no one has pointed out any errors before, but that doesn't mean they don't exist. 🙂

The formula is shown on the spreadsheet:

b' = (e * f^2) / (k * z) where b' is the effective base length of the rangefinder, e the visual acuity (0.0003 at approx. 1 arcmin), f the focal length, k the aperture and z the circle of confusion (0.020mm for APS-C, 0.030mm for film)

 

[splitimageview]

That chart shows errors for the MP
EBLs for the MP:

.58 39.7
.72 49.3
.85 + 1.2 magnifier 59.2
MP (.72?) + 1.5 magnifier 74

Problem is .85 + 1.2 magnifier, the result of 59.2 is incorrect. That would be the result of the .72 + 1.2 magnifier.

So, kinda discounting what I am seeing here. There's a whole lot of numbers, some which may or may not be correct, that results in a whole lot of nothing.

All that matters is :
1. That your camera's rf is correctly calibrated
and once that has been achieved
b. the EBL.

There are multiple MP models listed:

0.58x MP with an EBL of 39.7, column O
0.72x MP with an EBL of 49.3, column P
0.85x MP with 1.2x magnifier, EBL 69.9, column Q (this originally showed a 0.72x with a 1.2x magnifier but has been updated to correctly show 0.85x)
0.72x MP with 1.5x magnifier, EBL 74.0, column R

The effective base length is determined by the RF baselength (in this case 68.5mm) multiplied by the magnification, so for example the standard 0.72 MP would be 68.5 x 0.72 which would be 49.3.

When using a viewfinder magnifier the equation would then be the RF base times the viewfinder magnification times the viewfinder magnifier magnification.

Note that the 135/2.8 has goggles (i.e., a viewfinder magnifier.) The sheet needs to be updated to reflect this, although I'm not sure what the magnification factor is on this lens. EDIT: since updated to reflect 1.5x.

 

[Pioneer]

There are multiple MP models listed:

0.58x MP with an EBL of 39.7, column O
0.72x MP with an EBL of 49.3, column P
0.85x MP with 1.2x magnifier, EBL 69.9, column Q (this originally showed a 0.72x with a 1.2x magnifier but has been updated to correctly show 0.85x)
0.72x MP with 1.5x magnifier, EBL 74.0, column R

The effective base length is determined by the RF baselength (in this case 68.5mm) multiplied by the magnification, so for example the standard 0.72 MP would be 68.5 x 0.72 which would be 49.3.

When using a viewfinder magnifier the equation would then be the RF base times the viewfinder magnification times the viewfinder magnifier magnification.

Note that the 135/2.8 has goggles (i.e., a viewfinder magnifier.) The sheet needs to be updated to reflect this, although I'm not sure what the magnification factor is on this lens. EDIT: since updated to reflect 1.5x.

Thanks for your help trying to explain this. This certainly takes rangefinder focus accuracy to a new level of complexity from my perspective. I will have to take some time with the calculations to get more comfortable with this. A quick comparison of the numbers between camera and rangefinder base lengths seems to show some unexpected results, but that certainly doesn't mean they are wrong, just unexpected.

 

[splitimageview]

Which ones are unexpected?

There are only two cameras that can have problems with the 50/1.1, one of which would likely have a blocked viewfinder anyway (CL) and the other is more of a specialty wide angle body (R4.)

 

[Pioneer]

Which ones are unexpected?

There are only two cameras that can have problems with the 50/1.1, one of which would likely have a blocked viewfinder anyway (CL) and the other is more of a specialty wide angle body (R4.)

Relax. The chart is fine. It is just a lot for me to absorb quickly, especially when I am really supposed to be putting up Xmas decorations, not cruising the interweb and reviewing camera spreadsheets. 🙂

From what I can tell it really doesn't give a lot more useful information then the EBL numbers do, it just applies it to each lens. The EBL is still the determining factor. A longer effective base length means you can more accurately focus faster or longer lenses.

The unexpected part is when I look at the results for the MP with the 0.58 finder. I find it a bit confusing that this rangefinder can be expected to accurately focus a 50mm f/1 (or 1.1 since there is not a lot of difference) yet is not expected to accurately focus a 75mm f/ 1.4 lens. Even the CLE, with an EBL of 28.8 is supposed to be OK with a 50mm f/1 lens, but not OK with a 60mm f/1.2.

To me these results seem a bit odd and indicate that the calculations are more influenced by focal length than aperture. I don't doubt that the calculations are correct I just find the assumptions behind the calculations to be contrary to my own expectations.

Like I said, your spreadsheet is fine. It is more a function of my own expectations of focus accuracy between cameras with different effective base lengths. I just would not have expected to see that much difference between a 60/1.2 lens and a 50/1 lens.

EDIT - Of course when you factor in a half blind old Grandpa like me then your entire chart could be suspect. I have trouble focusing a 50/1.4 lens wide open with an M3. 😀