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dfarkas

New In-Depth Leica T Review

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Thanks a lot for this well written and informative review .

 

I haven't quite yet understood how the control dials on top are used, and what they can control. Can they be set so that they are scrolled will adjust aperture and shutter speed? How is this information displayed? From the review I do not understand the following: "The control dials require a two-step activation.". What is the first and second step?

 

Sorry for being a bit slow

, perhaps reviewer or others can clarify?

 

Yes, they can be set to a number of functions by simple touching them. Look at the video inside the review and he shows how this is done.

It starts around 6:40 in:

 

The info is displayed on the top of the screen.

Edited by digitalfx

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1. Not borne out by other users and flogged to death in the XV forum ..... it's no better ... or worse than most AF cameras ... including the A7r .... and is entirely dependent on subject matter, ISO and lighting

 

2. Never had this happen.

 

3. Image review is based on the JPG setting ..... just use a higher one ! OK so it's a nuisance having a card full of 7Mb JPG's when you only use DNG, but so what .....

 

4.The leave it switched on ! Sony A7r is slower.... From switch on to taking an image on mine is well less than second .........

 

5. Sony A7r is similar ..... just press the shutter (or switch on) when you see a suitable subject and by the time you get the viewfinder to your eye it will be on........

 

You are a very hard man to please John .....

Normal for John. Nothing Leica does will ever please him. I think, however, that he is pleased that he elicits responses. My experience with the A7r is that it is capable but I am disappointed that it smears with many Leica lenses, and I think (hope) the T is going to be my cup of tea.

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Yes, they can be set to a number of functions by simple touching them. Look at the video inside the review and he shows how this is done.

It starts around 6:40 in:

 

The info is displayed on the top of the screen.

 

Beat me to it!

 

Yeah, the dials need to be rolled once (they have small detents so you can feel them turning) to bring up their function, then they can be rolled either way to change settings.

 

I understand the need for the first activation, but I still wish there was another way to assign/change functions without slowing down use.

 

Hope this, plus the video clarifies a bit.

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My experience with the A7r is that it is capable but I am disappointed that it smears with many Leica lenses, and I think (hope) the T is going to be my cup of tea.

 

Okay, this is a little off-topic for Leica T discussion, but.....

 

I think I need to write an article (expose) on why Leica wides don't work well on A7r. I've explained it to quite a lot of folks one-by-one and there is always that "ah-ha" moment once it's all laid out.

 

The bottom line is this: the sensor in the A7r was pulled from a DSLR (D800), which is well-suited for retrofocus, telecentric lenses. Leica wides are non-retrofocus and project light rays onto the sensor with an extremely high angle of incidence as they get farther away from the center.

 

The CMOSIS/Leica-designed sensor in the M240 is specifically tailored for these lenses, as well as highly telecentric lenses like the R lenses. Many people don't give Leica proper credit in the sensor department, but the sensor in the M240 is actually one of the most advanced, if not the most advanced, FF CMOS sensor design out there. It is certainly the thinnest, by far, with the shallowest pixel well depth, and has a very unique egg-shaped microlens structure. Both of these innovations allow the sensor to be unaffected by the angle of light coming in.

 

Make sense?

 

To bring this back on topic to the Leica T, it works great with M lenses.

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Yes we've seen this before but is it correct that the micro lens design in the T is not optimised for M lens use in the way it is in the M?

 

That then begs the question that if it is not, how does the T cope with the M incident angle issue or does it only work - sort of - because the T is not full frame?

 

I remember when MFT first came out, some of us (me included) got a little over-excited about using M lenses on a Panasonic G body, a solution which the T replaces. On MFT, the edge performance with M wides was pretty dire, especially on the 28mm Summicron.

 

So how does the T deliver good edge performance with M wides (assuming that it does) if the sensor is not optimised for them?

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With the T not being full frame, it will have the same benefit of cropping out the outer zone that other APS-C cameras that worked OK with M lenses did, such as the NEX-5N, NEX-6, etc. This is where the light rays projected by many wide M lenses is very steeply inclined.

 

It's not so much the micro lenses that are critical (they help put more light in each pixel, which helps), it's the thickness of the glass layers over the sensor. In M bodies, this glass is as thin as possible, which is why M cameras have IR contamination problems, including the M240 (from my experience shooting runners wearing black synthetic material).

 

There's a great explanation of how this works in this paper by Zeiss (pdf)

 

Check pg. 12:

 

Lenses with a very large beam tilt react in a much more sensitive manner to a change of refractive index in the image space caused by filter plates in front of the sensor (such as low pass and IR-blocking filters). If the filter plate is not considered in the design of the lens, the edge definition will suffer. The effect of the additional path through the glass grows exponentially with the beam inclination. A Distagon which never achieves more than 20° beam tilt in the corner of the image reacts more tolerantly than a symmetrical wide- angle lens, which might reach a 45° tilt. This is why filters in digital Leicas are very thin – to remain compatible with older optics.

 

If the filter is significantly thicker, the contrast transfer for the image edge becomes worse for tangential structures. In the graph of the curves, this looks like the old retrofocus lenses but is caused by astigmatism rather than lateral chromatic aberration. The focus is shifted to greater distances for tangential structures by the additional path through the glass. If the best edge definition is to be achieved, then all that can be done is to stop down further.

 

Based on the single 24mm Elmar DNG kindly supplied by David, it seems to me the T does quite well with wider M lenses, however, in that file I do see faint signs of some nervousness at the edges.

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... So how does the T deliver good edge performance with M wides (assuming that it does) if the sensor is not optimised for them?

Yes good question indeed. If the T's sensor were not somewhat optimised for M lenses, as stated like an obvious fact elsewhere, a difficult lens like the CV 21/4 would have red edge or cyan shift issues, which is not the case according to Sean Reid.

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As a rule, modern mirrorless systems are designed to minimise incident angles – mounts with large throat sizes, near telecentric lenses with large rear elements etc.. And that is what the microlenses are optimised for. It would make no sense to optimise microlens shift for large incident angles in the corners as that would be detrimental to the quality delivered by the system’s own lenses. But then of course, the outer reaches of the image circle of an M lens would be outside the area of an APS-C sensor anyway, so this is less of an issue than with a 35 mm sensor.

 

On the other hand it surely helps when the sensor is a 16 MP chip. The higher the MP figure and the smaller the pixels, the higher the risk of optical crosstalk.

Edited by mjh

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Hi Mark

So how does the T deliver good edge performance with M wides (assuming that it does) if the sensor is not optimised for them?

 

They aren't telling us - but it does.

I suspect that it's to do with the cover glass rather than the sensor itself? - it may also be to do with the very large lens mount?

 

all the best

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They aren't telling us - but it does.

I suspect that it's to do with the cover glass rather than the sensor itself?

Very likely I would think. Keeping everything on top of the chip as thin as possible is generally a good idea when dealing with large incident angles. And it doesn’t mess with small incident angles.

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