Question about the Rangefinding Mechanism

[deirdre]

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I don't expect high accuracy out of Wikipedia, but the mirrorless page on Wikipedia lists an M8 and an M9 as mirrorless designs.

 

It's my understanding that rangefinders traditionally have used a pentaprism for the second optical path, thus they wouldn't qualify as a mirrorless design. That said, it's also possible the M8 and M9 are doing something non-traditional. I'm too new to Leica to know.

 

Now I'm curious, though: did they change from the pentaprism? Or no?

[Rusted Chrome]

The "mirror" is the one in front of the shutter that allows an SLR user to see "through the lens." The viewfinder on a rangefinder type camera is a whole different thing. "Mirrorless" means there is no mirror to move out of the way when you press the shutter button.

[deirdre]

I understand how SLRs work, but why consider the M8 and M9 as MILC and not earlier models? Yes, I know analog vs. digital, but if the mechanism is essentially unchanged in the M8 and M9, then pretty much all rangefinders should be on that page.

 

The µ4/3 and so on are mirrorless, but I can't see a rangefinder as generally fitting that description.

[diogenis]

What exists in M8/9 is the same as it exists in M6/7.

In fact the design is an evolution from a very old model, the M3.

The difference with an dSLR is huge. Optical path for viewing is different to what the camera pictures. In a dSLR you see as well as you shoot from the same lens using a retractable mirror

[deirdre]

What exists in M8/9 is the same as it exists in M6/7.

In fact the design is an evolution from a very old model, the M3.

 

I knew about the design going back that far, but I just didn't know if there was something important about the way the rangefinder worked in the M8/M9. Sounds like there's not.

[ho_co]

At one time the distinction in "serious" cameras was CRF or SLR.

 

Now the CRF and SLR haven't changed, but we have SLR-like cameras that don't have mirrors. The earlier name for them was EVIL, Electronic Viewfinder Interchangeable Lens cameras, which to me seems a clearer distinction than calling them simply "mirrorless."

 

Your take is absolutely correct. All rangefinders, screw-mount, bayonet-mount, Leica, Contax etc are definitely "mirrorless."

 

The name will eventually settle down, but since Leica is still the only reference standard in the coupled-rangefinder world, the usage may end up not taking any notice of it, or trying to shoe-horn it in 'anywhere it fits.'

 

 

And BTW, the prism system in the M camera isn't actually a pentaprism. A pentaprism is used to invert an image in an SLR. But I understand there are also SLRs that use mirrors to do the same thing for cost reasons.

[deirdre]

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Okay, I was thinking pentaprism because I'd seen a diagram of a rangefinder that showed one. If this diagram is accurate, looks more like a trapezoid.

 

That nit aside, I've always assumed, and perhaps I'm incorrect, that several of the faces of a prism used in a finder are mirrored, but maybe it's the housing that's mirrored. Or maybe I'm just wrong, it's happened.

 

Anyhow, "mirrorless" in this context seems to be less precise than EVIL, which is what the category is better described by. Then again, since some of us have discovered Leica through our EVIL cameras, maybe it's still useful.

[giordano]

And BTW, the prism system in the M camera isn't actually a pentaprism. A pentaprism is used to invert an image in an SLR.

 

For completeness it's worth mentioning that the prism behind the M rangefinder window does invert the rangefinder image. The light path inside it is the same as in SLRs where the viewfinder eyepiece is at a 45 degree angle (e.g. some Alpas and Hasselblads), although it's very different from a regular SLR pentaprism.

 

But I understand there are also SLRs that use mirrors to do the same thing for cost reasons.

 

Yes, starting in the 1940s (Wrayflex) if not before.

[delander †]

That wiki page is a confusing mess. The Leica RF is distinct from other 'mirrorless' cameras which provide a view of the subject through the lens. The M cameras should not even be on that page, a link to a RF page should be suffcient.

 

Jeff

[theno23]

There are also EVIL cameras that are not mirrorless, like the new crop of Sony A33 and A55. They have SLR-style (but half / "pellicle") mirrors, and no optical viewfinder. It has the same sort of flage distance as an SLR, but the mirror doesn't have to move to take the shot.

 

In a rangefinder there's no mirror in the optical patch between the lens and film/sensor, which is the important thing in the term mirrorless. Means you can have the short flange distance, which contributes to the small size of rangfinders and m4/3 style cameras.

 

- Steve

[deirdre]

There are also EVIL cameras that are not mirrorless, like the new crop of Sony A33 and A55. They have SLR-style (but half / "pellicle") mirrors, and no optical viewfinder. It has the same sort of flage distance as an SLR, but the mirror doesn't have to move to take the shot.

 

Also a good point. That design goes back to the 60s, but EVIL is definitely a better fit for that acronym-wise.

 

In a rangefinder there's no mirror in the optical patch between the lens and film/sensor, which is the important thing in the term mirrorless. Means you can have the short flange distance, which contributes to the small size of rangfinders and m4/3 style cameras.

 

Which is what eventually led me here, because I kept seeing people using great Leica lenses on µ4/3 cameras.

[alexmann]

With an SLR you are essentially looking directly through the lens on the camera, via a mirror, and focussing it to a point which, when the mirror flips up, will be the same focus point on the film plane. So you are focussing, visually, the actual lens. With a rangefinder the mechanism basically measures two angles (think left eye and right eye) and works out a distance based on those values. The rangefinder is linked to the focussing ring on the lens and when these values match the two focussing patches match up in the viewfinder. That is why bodies and lenses occasionally have to go back to Solms to be matched up. A bit potty but it works!

Regards

Alex

[ho_co]

In addition to what's already been said, Stefan Daniel himself mischievously refers to the M9 as a "mirrorless camera" in the interview at

.

 

 

BTW. Dierdre, welcome to the forum.

 

As you see, we've all got ideas that we're ready to share.

 

We're glad you found us.

[hvacigar]

It really gets confusing when people label SLTs as mirrorless like the RFs. Now where do you place those cameras like the new Sony A55 and A33? Mirrorless or no?

[diogenis]

I dont like the term "mirrorless". Maybe he said it in an effort to claim customers from the m4/3 or the small compact cameras, as it seems these gain more ground to the SLR. But by doing so, he is focusing on things that Leica's cameras lack. He is not focusing on the product's main qualities.

No reason trying to compare to a dSLR, unless the dSLR is the limit.

[deirdre]

Thanks for the welcome.

 

I think one reason Leica may have mentioned mirrorless is the partnership they have with Panasonic. I think Panasonic does have products that complement Leica's line, getting both the lower-end consumer all the way up to the low end of the midrange with the µ4/3 and into the video camera market.

 

It was seeing Leica's name all over Panasonic lenses, seeing people using adapted Leica lenses on µ4/3 that got me on this quest. So, never having handled one, I went to the Leica Akademie. Now it's just a matter of time.

[ho_co]

... Now it's just a matter of time.

Once it's got you Deirdre, you're done for!

[adli]

Mirrorless is referd to as a camera consept where you don't use a mirror in the in the optical path, as oposed to the market dominating SLR design.

 

Leica M is a camera design based on a rangefinder concept. This concept dates back to before SLR domated the marked and thus is not a design where the concept name incorporates a reference to a dominating system. Rangefinder was the dominating 35mm system when Leica M was launched.

[Bo_Lorentzen]

LOL.. sorry to hear you got bidden by the rangerfinder bug.

 

"penta prism" as used in cameras, im pretty sure refers to the number of surfaces in the prism used in a SLR camera, the one used in the rangefinder diagram is not a penta-prism but some other-prism. I'm pretty sure about that, with room to be wrong.

 

Personally Im getting bugged by the SLR / dSLR groups, they both operate on the same concept with different type sensors, but my nikon SLR lenses seems to work just fine on dSLR cameras.

 

The mirror-less reference to the leica M cameras, seems much deeper than just that... it was clearly a joke, but at the same time there is a shockingly small step to actually do something with a M style mirror-less camera. Im sure this did not just pop off the top of his head.

 

.

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[giordano]

"penta prism" as used in cameras, im pretty sure refers to the number of surfaces in the prism used in a SLR camera, the one used in the rangefinder diagram is not a penta-prism but some other-prism. I'm pretty sure about that, with room to be wrong.

 

It's arguable whether the "pentaprism" that most SLRs contain is actually a prism at all. It's the wrong shape to be a prism in the geometrical sense, and unlike a classic optical prism it's not used to refract light. It has eight surfaces, not five, and three of them are silvered (aluminised?) to reflect the image of the focusing screen. It's called a pentaprism because the design was based on a plain five-sided prism by replacing one surface with a pair that form a 90 degree angle.

 

The prism behind the rangefinder window on M2-M9 also has three reflecting surfaces, two of which form a 90 degree angle in the same way as on the SLR pentaprism, but geometrically it's quite different and has only seven surfaces.

 

The prism behind the rangefinder window on the M3 is different again: it's a true pentaprism (five sides, seven surfaces in total) without the pair of surfaces at 90 degrees. Two of the sides are silvered to reflect the rangefinder image.

 

This page rangefinder issues has good diagrams of the LTM and M range/viewfinders.