Understanding Lens Designations

[Robert E]

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Hi guys, could someone please help me to understand the lens designations written on the lens by Leica?

Example: I had an SL, now have an SL2. With the IBIS I wanted to try some different lenses available. So I purchased a TL VE 55-135mm zoom lens. Now I realize this lens was made for the TL or CL camera, which is an APS-C body. So, the lens has embossed on it: "55-135" and of course on the box and paperwork. When you look at the description of the lens, say online at B&H, it says: "35mm equivalent of 80-200mm". So I'm assuming they mean on a 'cropped' body of a TL or CL, it's an 80-200mm? If so, why is it labeled 55-135mm?

When I use it on my SL2 it automatically goes to APS-C mode, which I also understand, and the images are great. But what am I getting? A 55-135mm focal length, or an 80-200mm FL? I'm only interested in what it actually is on an SL2? If it is indeed, 80-200mm, why do they even designate the lens as: "55-135mm". When is it a 55-135mm lens? I'm confused on that.

Any help appreciated and sorry if this is a dumb question, I just don't understand it?

Thanks!

Robert E

[Donzo98]

It’s the equivalent of 82.5-202.5 on a FF body.

You need to multiply 55-135 x1.5.

it also only uses the APS-C part of the sensor... which results in a 20mp image not 47. 

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[Robert E]

Hi Don,  thanks for that info. Two questions still go unanswered:

1. When is the lens a 55-15mm? Example: on a Leica CL body is it a 55-135 focal length lens?

2. If it is an 82.5-202.5 on a FF body, is that still true when the FF body automatically goes to APS-C cropped mode? 

Thanks to any that can clarify this.

 

 

[HeinzX]

The focal length does never change - it is an physical attribute of the lnns and does not depend on the sensor. What does change on different sensors is the angle of the photo, not the focal length. Using an extender would change the focal length really, that is another story. Does that make a difference ? Yes it does, the picture will not be exactly the same it will be similiar. Using a 50 mm lens  for full frame on a full frame sensor will result in a picture with 50 mm. Using it on  a APS-C camera would be the same focal length but result in an angle of a 75 mm. That means you get a crop of the 50 mm picture which would be achieved by using it on a  full frame camera.  But it is not the same impression as using a 75 mm lens on a full frame camera .

Edited June 1, 2020 by HeinzX

[FlashGordonPhotography]

Lens designations for the L mount cameras:

L mount is the designation for the actual physical lens mount. All L mount lenses fit all L mount cameras. You have TL and SL subsets.

SL: Lenses designed to cover the 24x36 format (incorrectly labelled *full frame*). Any Leica lens with the designation SL can cover a 24x36mm sensor completely. If you want lenses that cover the full sensor on your SL these are what you need, or the Sigma and Panasonic options.

TL: Lenses designed to cover an APSC sensor. These lenses will work on 24x36mm sensors but crop part of the sensor to APSC size. They cover the full sensor of cameras like the TL and CL. If you put this lens on your SL/SL2 you use only an APSC sized part of the sensor. They will work perfectly but you will be foregoing some of the sensor area and therefore resolution will be lower.

If you put an SL lens on an APSC body, because the lens can cover the entire sensor anyway, you'll get no difference from using a TL lens with the same focal length. The 35mm SL lens has the same angle of view as the 35mm TL lens on an APSC sensor because both lenses cover the APSC sensor completely. SL lenses do need to be bigger to be able to cover a 24x36mm sensor so you'll usually find SL lenses are larger and heavier for the same focal length.

Summilux: Lenses that have a maximum aperture between f1.4 and f1.8.

Summicron: Lenses with a fastest aperture of f2.

VE (vario elmar). Zoom lenses with a variable widest aperture. Usually a bit faster at the wide end than the long end. ie: f3.5-3.6 or something similar.

***note*** L mount lenses from other manufacturers (Sigma and Panasonic) do NOT follow Leica's naming schedule. Also Leica have a bunch of other lens terms (Noctilux, Elmar, Summarit etc..) but these aren't used in the SL line yet.

Equivalence:

The reason you're getting two ranges for the TL55-135 is because they tell you what it actually is (55-135) and what framing it gives compared to an *equivalent* lens on a 24x36mm sensor. The 24x36mm sensor seems to have become the benchmark for focal length measurement and most other sensor sizes give the numbers compared to it. It has also gotten the technically incorrect name *full frame*. It's wrong but we're stuck with it. All sensors except the Digulux are full frame, technically but when you see it on a forum they usually mean a 24x36mm sensor. It's also called 35mm (from the film days), 135 format and a few others.

A 24x36mm sensor generally has 1.5x the surface area of an APSC sensor so if we multiply 55-135 by 1.5 we get about 80-200.

Your lens is a 55-135mm lens designed for an APSC sensor. The 80-200 refers to the lens you would need to have on a 24x36mm sensor to get the same angle of view.

Confusing, huh??? 

Gordon

p.s. It gets worse. Someone will start talking about the *equivalent aperture* and a 15 page thread of half truths will follow.  

Edited June 1, 2020 by FlashGordonPhotography

[Robert E]

Gordon,

That was great, thanks so much for your input, appreciate it.

Robert E

[Jeff S]

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And just because a lens is labeled, say, 50mm, doesn’t mean it’s exactly 50mm; could be off by a mm or so.  😳

In the end, best to ignore the labels, math and conversions and just learn how a given lens frames the scene and renders the pic on your camera.  
 

Jeff

[Robert E]

Jeff, oh no, us Leica people could never do something as simple as that! ☺️

[pgk]

16 hours ago, FlashGordonPhotography said:

p.s. It gets worse. Someone will start talking about the *equivalent aperture* and a 15 page thread of half truths will follow.  

Am I allowed to point out that focal length changes as you focus closer? (😀)

[Exodies]

So if I trim my print with scissors that will increase the focal length of my lens.