M3 centre rectangle frame box question?

[stvn66]

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Hi,

Can someone please tell me what the significance of the 2 x smaller boxes that are attached to the M3 centre rectangle as circled?

I have seached online but cannot find any reference.

Thank you.

 

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[frame-it]

DOF markers for 50mm top marker for f16, bottom marker for f5.6

you don't have the manual?

The rangefinder also enables you to check whether a subject in front of, or behind, the point of sharpest focus will be acceptably sharp or not. For this you use the projections at the top and bottom edges of the rangefinder field rectangle. These projections show the depth-of-field for a standard 50 mm lens, the lower for the all-around aperture of f/5.6, the upper for f/16. After focusing on the subject of major importance the appropriate projection is superimposed on other subjects before and/or behind the point of focus. If the separation of the double image outlines still lies within this projection the image will be acceptably sharp. To use this special device most effectively it is advisable to test only the edges of the foreground or background subjects.

[stvn66]

No, I don't have the manual.

Thank you very much for the info👍🏻

[250swb]

7 minutes ago, stvn66 said:

No, I don't have the manual.

Thank you very much for the info👍🏻

https://butkus.org/chinon/leica/leica_m3/leica_m3.htm

to get a free .pdf of the manual

 

 

Edited May 27, 2024 by 250swb

[adan]

Just bear in mind that those M3 DOF viewfinder "rulers" are based on 70-year-old standards - smallish prints in the range of 10x15cm (4x6 inches) to 20x30cm (~8x12 inches).

Things that "look sharp" in the smaller sizes may be visibly outside the range of the DOF (blurry) if printed larger, or viewed (as scans) at full resolution.

[TomB_tx]

Also be aware not all M3s have these DOF rulers - they first appeared with the M2 (about 1957) and then were added to the M3 production. So M3s made before 1957 do not have them unless they had a VF update. My 1955 DS doesnt have them, but my 1960 M3 SS does.

[Michael Geschlecht]

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Hello stvn66,

Welcome to the Forum.

And f5.6 & f16 are NOT reflective of the depth of field when using other lenses of OTHER focal lengths. Including OTHER focal length lenses with fixed or removable "goggles". With other focal length lenses with or without "goggles" those gaps represent a variety of different f stops.

f5.6 & f16 are only correct with 50mm lenses.

IF you want to try this system with a 50mm lens: You might want to try a system that some people from the middle of the 20th Century & later have done when they wanted "sharper" pictures on film:

Set the aperture to the number you want to use.

And, then, use the depth of field scale inside the range/viewfinder window, or on the lens barrel that is 2 (two) stops more open to decide where the acceptable depth of field is..

So: Using the scales the new way inside the range/viewfinder window: A rangefinder separation at the wider gap would show you the acceptable depth of field for a 50mm lens set at f32. And the smaller gap would show you the rangefinder separation gap acceptable for a lens set to f11. 

If you are using the scales on the lens barrels: If the lens is set to f4: Use the depth of field scale for f2.

Best Regards,

Michael

[stvn66]

Many thanks to everbody for your input, much appreciated 🙂

[Greenhilltony]

On 5/28/2024 at 4:47 AM, adan said:

Just bear in mind that those M3 DOF viewfinder "rulers" are based on 70-year-old standards - smallish prints in the range of 10x15cm (4x6 inches) to 20x30cm (~8x12 inches).

Things that "look sharp" in the smaller sizes may be visibly outside the range of the DOF (blurry) if printed larger, or viewed (as scans) at full resolution.

At least they are stricter than the DOF scales printed on the lens barrel, if you compared.

 

On 5/28/2024 at 10:26 AM, Michael Geschlecht said:

And f5.6 & f16 are NOT reflective of the depth of field when using other lenses of OTHER focal lengths. Including OTHER focal length lenses with fixed or removable "goggles". With other focal length lenses with or without "goggles" those gaps represent a variety of different f stops.

f5.6 & f16 are only correct with 50mm lenses.

I used an app on iOS to calculate the DOF and found out that for 40mm lenses the boxes are indicator for F4 & F11 and for 35mm lenses they are F2.8 & F8.