Leica SL: Using the new 35mm Summilux-TL crop lens
Many people have bought Leica's new SL solely for use with manual M lenses. It makes a very good job of this and, if your preference is for an electronic viewfinder, the SL is much superior to using the M with its antiquated slot-in EVF. Perhaps it is not as satisfying ultimately as rangefinding but it is certainly getting there. That whopping 4.4MP viewfinder is capable of winning over the most sceptical of rangefinder nuts, present company included.
Above all, as I wrote last week, the SL introduces new and exciting possibilities for super-fast glass such as the Noctilux. With a four-stop speed advantage over the M (aggregating lower ISO sensitivity and the newly announced electronic 1/16000s shutter), the SL is a winner and benefits all fast lenses, even the f/1.4 Summilux discussed here.
But what of native autofocus primes? There ain't any, in short. The nearest on the roadmap is the 50mm Summilux which is at least eight months away.
Yet there are two excellent primes in the T stable that fit the SL and work like natives. Both offer fast autofocus and excellent image quality. One stands out, however: The new 35mm Summilux-TL f/1.4 ASPH, has Sherman-like build and better complements the SL than it does the T (at least in terms of size). Big and moderately heavy (455g) it may be; but it is a lightweight compared with the full-frame 50mm Frankenlens they are putting the finishes to in Wetzlar. Twice the size, twice the weight, twice the price. This is perhaps a slight exaggeration but you get the message.
For the time being, if you want excellent, fast autofocusing glass for your SL you have but one choice. The 35mm Summilux-TL is a rather less than nifty fifty for the big bruiser but a very solid performer nonetheless. I have been trying it out on the SL.
The accompanying examples illustrated detail resolution by introducing large crops as will be obvious, mostly down to a miserable 0.5MP. This represents a crop too far and is extreme, something you would not wish to do with any lens except in emergency. All shots are hand held and it is possible better results could have been achieved using a tripod (neither camera nor this particular lens has stabilisation). Some camera shake is obvious in the enlargement of the William Morris sign below, for instance. But, even with a full-frame file, you would not expect perfect resolution at such magnification.
First, though, a short word on the Summicron-TL 23mm f/2 ASPH which has been around since the launch of the T in 2014. It is also a great lens, 35mm-equivalent on the T (and the SL), much lighter than the new Summilux. This lightweight build is obvious as soon as you pick up the lens. It is made in Japan whereas this new metal Überlux is an all-German affair. Surprisingly, though, the 35mm Summicron is only £300 cheaper than the £1,650 Summilux. This, to my mind, makes the longer and faster lens a stonking buy for SL addicts. It is also the "standard" focal length that many still prefer.
Below: Full size and large crops, click to enlarge
Furthermore, the 'Lux is a perfect match for your new SL. No one other than a Leica Anorak with 20:20 vision would think for a moment that it wasn't really made for the big camera instead of the puny T. I’ve been using a silver version which looks particularly fetching on the rather bland and unexciting black acreage of the SL.
The elephant is the room is that the Summilux-TL is a cropped lens, designed to work with the smaller APS-C sensor of the T. As a result, although it performs surprisingly well on the SL, the lens is covering only the centre of the larger sensor.
Now we are most of us familiar with using full-frame M lenses on APS-C devices (Leica T, Fuji X, for instance) or even on MFT cameras from Panasonic and Olympus. We all know about crop factors and that a full-frame lens grows longer the smaller the sensor (so a 50mm M lens is 75mm on APS-C and 100mm on an Olympus) but we are less familiar, for want of the availability of test subjects, with the effect of mounting a cropped lens on a full-frame camera.
More crops (click to enlarge)
Well, I have to say, it's an odd one and not what you might expect. Ask any expert (I have done on several occasions) and there is a palpable pause for thought. A cropped lens such as the 35mm Summilux-TL acts as a 50mm equivalent on the T. But it is still equivalent to 50mm when hooked up to the SL (not back to 35mm as popular prejudice might have it). You could be forgiven for imagining that the crop factor might work in reverse. It doesn't.
So, what we do have in the 35mm Summilux is a 50mm lens for the SL, covering only the central part of the sensor. And this isn't 16MP as more schoolboy maths might predict. No, it is considerably less. A T lens on the SL has to make do with only 10.3 of the available 24 Megapixels in the SL’s sensor. Bear in mind, though, that the pixels on the SL are larger than those on the T. To what extent is the sum of all this prestidigitation a disadvantage? Will you be tremendously short-changed using the TL lens on the SL? Will it perform better on the T, where it addresses the full 16MP?
I suspect there are many answers to this conundrum. There is no clear-cut answer to be had, it's just a matter of suck it and see. Yes, ultimately the TL lens is going to produce a smaller file on the SL than would be the case if it were made for the full-frame sensor. But no, in the real world it might not matter as much as all that.
Note: A full-frame SL file is 6000x4000 = 24MP; a full-sized shot on the SL from the cropped lens is 3936x2624 = 10.328MP while a file from the T is 4928x3264 = 16MP. This is therefore a crop of 1.55 in relation to the T’s 16MP sensor but a whopping 2.32 ratio compared with the SL’s 24MP sensor. No, I don’t fully understand either; ask me another.
Back to the conundrum. I have yet to answer the question to my satisfaction and today’s shots are mere foreplay. With the Summilux on the SL I have bagged some pleasing initial results, even allowing for that 10.3MP ceiling. In operation it is just like an SL prime would be, although such an animal has not yet been released from captivity. There is no doubt this is a great lens with impressive image quality, very pleasing bokeh and generally attractive rendition. Again I am reminded of the wonderful, neutral colour from all current German-made Leica digitals. I can believe it is a winner for the APS-C camera, but it is certainly no slouch on the SL.
The overall results are actually very good, in my opinion, and I have gained a lot of confidence in using the 35mm Summilux on the SL. Ultimate cropping is less of an option than it would be with a genuine full-frame file but I am not feeling short-changed in the slightest . Indeed I am by no means sure to what extent the T will do a better job, although I know full well that the 50mm SL prime, when it comes, will superior. It will have to be; but it will come at the penalty of size, weight and cost. For real-world shooting (without having a need for billboard-sized prints), this cropped lens could be just what you are looking for to go with your SL.
The next step is to lay hands on a T body to see how extra file size makes a difference to image quality—more smaller pixels compared with fewer larger pixels. It will be an interesting experiment and I will produce a follow-up article as soon as the testing is finished. So far, though, I am quietly confident that this cropped lens is a major asset for SL owners.