ASP-C sensor with non native lenses?

[Brian C in Az]

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I have seen, on more than one youtube video, that when using T lenses on the SL the camera automatically switches from full frame sensor to ASP-C size. The software does this automatically as soon as the lenses are attached. I haven't read that in any Leica literature, but both videos were from pros who had learned that from the Leica Academy, so I'm taking that as fact.

My question is, "Does the camera also switch to ASP-C when using non native lenses via an adapter?" How would someone know? Can someone with a T lens tell us is there a difference in file size?

Mechanically it makes sense that if you are using an M lenses that the available light image is smaller due to the smaller physical size of the lenses, same when using an R lens. 

[ramarren]

The SL does not automatically reconfigure the format when non-native lenses are used. If you're using any other Leica lenses using the Leica adapters, all the other Leica lenses are designed for FF format (or larger!) anyway, and if you're not using a Leica adapter, the body has no information about what you've hung onto the lens mount at all. 

The reason the SL switches to APS-C format when a T/TL series lens is fitted is that the body knows all about these lenses and their intended format based on information from the lenses' ROM. Leica always wants to preserve their lenses' imaging performance to be 'as designed,' so the body switches to the format that these lenses were intended for. 

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Mechanically it makes sense that if you are using an M lenses that the available light image is smaller due to the smaller physical size of the lenses, same when using an R lens. 

I'm not sure what you are trying to say in this sentence. R, M, and T/TL lenses transmit exactly the same amount of light at the taking aperture when the aperture setting is set to the same f/number on each of them. The physical size of the lens is irrelevant. 

Edited November 3, 2018 by ramarren

[Brian C in Az]

The image circle size is directly related to the physical diameter of the lens/ glass. An M lens is physically smaller, therefore, the image circle is smaller than the same image viewed through an SL lens of the same focal length and aperture setting.

 

If I am wrong, then why would ALL the SL native lenses be so much larger and heavier than the M lenses of equal focal length? Leica does not charge by the pound, so there must be a technical/ scientific reason/ need for the large objective lens size.

Edited November 3, 2018 by Brian C in Az

[Brian C in Az]

It would make perfect sense that the camera would default to a smaller effective sensor size automatically when a lens adapter is attached. As you stated, Leica designed the system to detect and recognize the T lenses limitations and appropriately adjusted the sensor to compensate. Therefore, when you attach an M adapter, the camera will know that you are using an M lens and would be able to adjust the sensor accordingly. The list of approved R lenses are all ROM lenses, therefore, the camera knows ideal sensor parameters and could theoricatally adjust accordingly.

Back to the original question.

How would we know if the SL is using the total area of the full frame sensor or if it reduces the effective size to ASP-C for M lenses or R lenses as it does for the T lenses?

I am thinking that Leica probably does alter the sensor's effective area or active area for each type.

[Leicaiste]

7 minutes ago, Brian C in Az said:

The image circle size is directly related to the physical diameter of the lens/ glass. An M lens is physically smaller, therefore, the image circle is smaller than the same image viewed through an SL lens of the same focal length and aperture setting.

No.

Leica M and SL lenses are designed to cover the same sensor size.

Full frame.

[Brian C in Az]

The M was designed for full frame size FILM. It is well known that the light is absorbed differently by a solid state sensor than it is by film.

You need to go back to the basics of how film absorbs light. It can absorb light at an angle. A sensor can only absorb light that strikes it vertically; perpendicular to it's surface. This is well documented and is scientific fact. The better designed (which Leica certainly falls into that group) digital lenses use a different shape lens closest to the sensor compared to the shape of the closest lens to film. The lens is shaped to bend the pight from it's normal angle and bend it to be vertical at the edges of the sensor.

 

Give me a complete explanation or scientfic answer other than just, "NO, my M lens is ....."

Edited November 3, 2018 by Brian C in Az

[Leicaiste]

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The sensor on the Leica SL, M9, M, M10 (etc.) and Q are of the same physical size.

[Leicaiste]

5 minutes ago, Brian C in Az said:

The M was designed for full FILM frame size. It is well known that the light is absorbed differently by a solid state sensor than it is by film.

You need to go back to the basics of how film absorbs light. It can absorb light at an angle. A sensor can only absorb light that struck it vertically, perpendicular to it's surface. This is well documented and is scientific fact. The better designed (which Leica certainly falls into that group) digital lenses use a different shape lens closest to the sensor than the shape of the closest lens to film. The lens is shaped to bend the pight from it's normal angle and bend it to be vertical at the edges of the sensor.

 

Give me a complete explanation or scientfic answer other than just, "NO, my M lens is ....."

Since the release of the first digital M, the sensors on the M's and SL have been adapted to the fact that the light rays are touching the sensor with an angle with M lenses.

This is well documented.

Edited November 3, 2018 by Leicaiste

[Brian C in Az]

That helps. Thank you.

Other brands are using a flat sensor and curved lenses based upon what I have read. 

I found no reference to Leica using a curved surface sensor

[Leicaiste]

1 minute ago, Brian C in Az said:

That helps. Thank you.

Other brands are using a flat sensor and curved lenses based upon what I have read. 

I found no reference to Leica using a curved surface sensor

Because they don't.

They move slightly the micro-lenses covering the pixels to the center.

[Leicaiste]

It is better explained here :

http://gmpphoto.blogspot.com/2016/01/the-future-of-sensor-technology-at-leica.html

 

Edited November 3, 2018 by Leicaiste

[Brian C in Az]

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The megapixel craziness has fortunately quieted down.  In the immediate future we will see sensors with less noise and higher dynamic range.  After that, according to Leica, another approach would be with curved instead of flat sensors.  This would allow for the design of substantially more compact lenses and also more compact camera systems.    Leica is convinced that this approach will lead them back to their roots: High quality in a compact design.  After all, that was Oskar Barnack’s goal when he designed the original Leica prototype, the Ur Leica, over 100 years ago.
 

The article concludes supporting my original thought that a flat sensor does in fact require a physically larger lens diameter.

[Brian C in Az]

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When using manual aperture lenses with no electronic coupling, like the M and R lenses, the camera utilizes a secondary, externally mounted light meter to approximate aperture information, similar to the M240. And, just like the M240, the SL uses this information to apply any necessary DNG shading corrections for specific lenses. This is further complimented by either automatic 6-bit detection of M lenses or by manual selection of uncoded M lenses and for all R lenses.
 

From the same author above, it appears that the camera is in fact designed to reduce the number of pixels used based upon which non native lens is employed. That explains why the camera requires a selection in the software of which non ROM lens is being used.

[Brian C in Az]

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 Starting with the S lenses and carrying forward to the TL and now the SL lenses, Leica started designing lenses for higher resolving power. The published specs show MTF testing up to 40 lp/mm, but internally, technicians now test up to 60 lp/mm, in order to guarantee the highest performance level for this latest generation of cameras, as well as what is to come in the foreseeable future.

Touching briefly on the TL lenses before getting down to the new SL models, Peter wanted to reiterate that there will continue to be TL lens development. “The lenses are quite good with great performance on the SL.” And, true enough, shortly after the SL introduction, two new TL lenses were announced: a 35mm f/1.4 Summilux-TL and 60mm f/2.8 APO-Macro-Elmarit-TL. I briefly tried the 35 Lux TL on the SL and it did seem excellent.

Leica SL (Typ 601) with new 35mm f/1.4 Summilux-TL ASPH - the camera automatically switches to APS-C mode with TL lenses mounted
Leica SL (Typ 601) with new 35mm f/1.4 Summilux-TL ASPH – the camera automatically switches to APS-C mode with TL lenses mounted

The first SL lens, the Vario-Elmarit-SL 24-90mm f/2.8-4 ASPH has more in common with the 30-90mm Vario-Elmar-S lens than the previous 28-90mm Vario-Elmarit-R. In fact, both zooms, the 30-90 S and the 24-90 SL, were designed by Dietmar Stuible, with the new SL lens loosely based upon his earlier S design. With 18 elements in six moving groups, four aspheric elements and eleven elements using glass with anomalous partial dispersion, the standard zoom is packed with exotic glass. And, the end result is probably the best zoom lens that Leica has built to date. Looking at the MTF charts for the new lens, you can see that even wide open, the lens is resolving 80% contrast at 40 lp/m. At all focal lengths. At both infinity and close focus. Yes, this is impressive, especially for a zoom. In fact, the MTFs stay very consistent at all distances, focal lengths and apertures. The lens has no weaknesses. Certainly none that I could see in any of my test shots. If the rest of the SL lenses are as outstanding as the 24-90 we’re in for a real treat.

 

Stuible also worked on the upcoming APO Vario-Elmarit-SL 90-280mm f/2.8-4, which looks to be quite an achievement. Taking up roughly the same physical dimensions as the legendary 280mm f/4 APO Telyt-R, the new zoom provides a 3x zoom range while maintaining stunning optical quality and offering a faster f/2.8 starting aperture, lightening quick AF and the same OIS found in the 24-90. The lens utilizes 23 elements in seven moving groups, with seven elements made from glass with anomalous partial dispersion. All zooming and focus is internal, with no change in the length of the lens.

Quoted from

http://gmpphoto.blogspot.com/2016/01/leica-sl-typ-601-review-professional.html

 

There is a definite advantage to using the native lenses. It appears the design specs, parameters, and ultimate performance of the new lenses do in fact offer enough technological advances to warrant trading up from the older R lenses to the latest SL lenses.

 

I noticed that thighslapper uses mainly native lenses now, though he experimented with non native lenses previously. Maybe he will chime in.

[LocalHero1953]

Lots of people use non-SL lenses on the SL. I use M lenses, and have in the past used R (non-ROM) lenses. The advantages of native SL lenses are not necessarily IQ, but fast AF, weather sealing, OIS (in the zooms) and the balance that comes from being designed together.

[BernardC]

It's actually very simple. The reason to use a non-native lens on the SL is that the lens offers a look that suits your images.

The SL, TL and S lenses offer a vert distinctive look, with very high local contrast and great flare control. It's a great look, but it's hardly the only look there is.

[Brian C in Az]

11 hours ago, BernardC said:

It's actually very simple. The reason to use a non-native lens on the SL is that the lens offers a look that suits your images.

The SL, TL and S lenses offer a very distinctive look, with very high local contrast and great flare control. It's a great look, but it's hardly the only look there is.

You are correct. I was thinking more along the technical aspect and any potential loss of IQ.

I appreciate everyone's input and plan to experiment and enjoy the SL. That's why we are all here and why the forum exists; for us to ask questions and share ideas and information.

No wrong way to enjoy your Leica.

[LD_50]

On 11/3/2018 at 8:18 AM, Brian C in Az said:

It would make perfect sense that the camera would default to a smaller effective sensor size automatically when a lens adapter is attached. As you stated, Leica designed the system to detect and recognize the T lenses limitations and appropriately adjusted the sensor to compensate. Therefore, when you attach an M adapter, the camera will know that you are using an M lens and would be able to adjust the sensor accordingly. The list of approved R lenses are all ROM lenses, therefore, the camera knows ideal sensor parameters and could theoricatally adjust accordingly.

Back to the original question.

How would we know if the SL is using the total area of the full frame sensor or if it reduces the effective size to ASP-C for M lenses or R lenses as it does for the T lenses?

I am thinking that Leica probably does alter the sensor's effective area or active area for each type.

The M lenses project an image circle that covers the FF sensor size (same size as 35mm film). SL lenses do this with better optics, weather sealing, and AF, hence the larger physical size. 

Leica doesn’t need to decrease the effective sensor size when mounting M lenses like it does with APSC lenses because of this. 

You would know if this was done by the decreased resolution you would end up with in the resulting files. 

[Brian C in Az]

9 hours ago, LD_50 said:

The M lenses project an image circle that covers the FF sensor size (same size as 35mm film). SL lenses do this with better optics, weather sealing, and AF, hence the larger physical size. 

Leica doesn’t need to decrease the effective sensor size when mounting M lenses like it does with APSC lenses because of this. 

You would know if this was done by the decreased resolution you would end up with in the resulting files. 

That makes sense and was basically the answer that I was looking for originally.

 

A new question emerged though, "Since Leica has designed the software to perform DNG shading when using M or R lenses on the SL, what does that do to the image and file?"

 

http://gmpphoto.blogspot.com/2016/01/leica-sl-typ-601-review-professional.html

6th paragraph down

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When using manual aperture lenses with no electronic coupling, like the M and R lenses, the camera utilizes a secondary, externally mounted light meter to approximate aperture information, similar to the M240. And, just like the M240, the SL uses this information to apply any necessary DNG shading corrections for specific lenses. This is further complimented by either automatic 6-bit detection of M lenses or by manual selection of uncoded M lenses and for all R lenses.

 

I'm not trying to say they are doing something wrong. I want to know what are the effects of the in camera software shading?

That could help people decide if they want/ need native lenses or if they would be more likely to prefer the effects of using an R or an M lens.

 

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Hallo,

Look here: Leica L-Mount

[LD_50]

DNG shading referenced in that link is likely vignetting correction and possibly correction for color shift on some lenses that are weaker performers on digital cameras due to ray angle concerns. 

There are quite a few sites where you can find comparisons of M lenses on the SL and the M cameras. Sean Reid I recall doing some detailed comparisons. 

You can also open the files in a few RAW converters that ignore the corrections so that you can see the impact of those software corrections.