This is Part II of my three part series on Zeiss/Contax lenses for video.

In my Part I article, I discussed cost and feasability considerations in regards to these lenses, and offered a few tips on how to shop for a set of your own Zeiss Contax lenses. In this Part II article, I’ll discuss resolution charts and my notes on how the lenses perform at various apertures. I’ll also discuss about the handling and aesthetic reasons why I chose to build my lens set around Contax.

My forthcoming Part III article will delve a little more into the look of a Zeiss/Contax lens, the aesthetic it lends to the image. I will include a few examples of bokeh and flare characteristics at certain apertures. Onward…

Resolution Performance
Here is a ZIP file of full-quality PNG framegrabs of a DSC Labs resolution chart, that show the performance of these Zeiss/Contax lenses on a Canon C300 camera. For comparison, I have included resolution frames of the Canon 85/1.8 and 50/1.4.

Some observations on resolution performance:
* Wide open at f/2.8, the 21mm is nearly as sharp in the corners as it is in the center. It carries this peformance all the way up through f/5.6. It’s clear why this 21mm lens has a good reputation for sharpness…sharp wide lenses are hard to find. For comparison, look at how the 28mm corners are obviously more soft than the center of the chart, at f/2.8. On the 28mm this improves as you stop down the lens to f/4.0, and looks significantly better by the time you reach f/5.6. This is typical behavior for any lens…wide open tends to be least sharp, and the middle of the aperture range tends to offer the best performance. And the 28mm is no exception.

* The 50mm looks quite sharp edge to edge, even at f/2.0 and surprisingly quite good when wide open at f/1.4. At 2.0 it’s nearly as sharp as f/2.8, but you can see the contrast drop a bit (don’t forget that contrast contributes to how sharp an image appears). F/2.8 is more contrasty. f/1.4 seems to drop contrast a bit more across the entire image, but it nearly holds the same sharpness as f/2.0.

* Wide open at f/1.4, the 85mm shows sharpness falloff in the corners, and edge to edge has lowered contrast. It doesn’t appear to be as sharp wide open as the 50mm. Corner sharpness gradually improves as you would expect as you stop the lens down to f/5.6, but even at that stop the corners are not as crisp as the center of the image.

* The 135mm at f/5.6 appears almost as sharp at the edges as it does in the center. Corner sharpness fades a bit, but doesn’t really drop off as the aperture is opened, until around f/2.8. Not at all surprisingly, contrast at f/2.8 is lowered, vs f/5.6.

* I have just recently purchased the Zeiss/Contax 100mm f/2.0, as well as the 35mm f/1.4. I do not yet have those lenses converted, so I unfortunately don’t have data for this writeup. However, from what I hear, both should perform very well. In fact, the 100/2.0 may be one of the best optical performers in the Contax line. I’m very keen to put them both in to use as soon as possible.

Physical Performance & Considerations
I have modified my Contax lenses with the Duclos Cine-Mod, but I’ve shot with them bone stock and Cine-modded. So I’ll be talking about both versions in this section.

Contax lenses are really well-built, with all metal construction, and a weighty, solid feel. They have a textured exterior that is very easy to grip. The iris is fully manual, and has click-stops at every full aperture stop. The focus is also fully manual, and rotates roughly 180-degrees on most of the lenses. This long focus rotation is really helpful for focus pullers, because you can actually make marks that aren’t millimeters away from each other. On a Canon stills lens, for instance, the distance between close focus and infinity might only be an inch on the lens barrel. That makes focus marks very difficult to mark and hit…being off just a hair on the lens barrel might mean that you are a foot or more off in terms of depth of field. Even stock Contax lenses solve this issue by providing a nice long focus pull. It’s not as long of a focus pull as your average cine lens…one thing that you’ll often see on a cine lens is that the first few feet of focus movement are a very long distance apart on the lens barrel. Contax lenses don’t offer that much travel, but they are a good compromise for an affordable stills lens.

If you simply want to add a basic focus gear to a stock Contax lens, I recommend the Wide Open Camera lens gears…they are cheap, and the universal multi-size works very well on these lenses. Just make sure that you position the zip tie bump on the opposite side of the lens from where you’d normally mount your follow focus. There are other models out there that don’t have a bump and can be used 360-degrees…Cinevate is one manufacturer that offers a 360-degree usable gear. I chose to have my Contax lenses cine-modded to add a (semi) permanent lens gear. This is a solid hard plastic gear that is locked tightly to the lens and gives you a standard cine pitch (.08) gear for your follow focus. It also is nice to grab when running lightweight without a follow focus.

Most of these lenses have very limited or no forward travel when you are racking focus. The 21mm and 28mm have no travel. The 50mm has very limited forward travel. I’d recommend using the lenses with a mattebox that either clips/threads right onto the lens itself, or has a rubber donut or mount that can give a few millimeters in either direction. In my experience, the lenses that have some forward travel are not a concern with your average mattebox, so long as there is a little play in the mattebox. And of course it’s not a concern at all for clip-on matteboxes. If I just need ND filters and the occasional grad, something like the Formatt Hitech filter tray is a nice pairing.

Another thing to be aware of when building your camera, is the difference in length for the various lenses. You’ll want to make sure that there is enough rods in front to accomodate the longer lenses (and your mattebox, if you are using one), as well as make sure that your follow focus can be positioned to accomodate each lens. Something that I’ve found helpful with the short lenses like the 50mm and the 28mm, is a follow focus with a gear that can be placed on either side of the gearbox. If the base of your camera protrudes forward (like the C300), or your baseplate is forward of the lens mount, you might need to position the follow focus gear on the rear side of the gearbox, so that it can reach over that protrusion to the lens gear. One follow focus that I shot with recently was the Genus Bravo system, and it allows you to swap the gear to either side of the gearbox in seconds, and without tools. It’s a lovely low-profile follow focus option for lenses like these.

Declicking the aperture is highly recommended for cine purposes…being able to smoothly ramp up and down the scale is hugely useful when setting exposure. Also, the ability to set half stops and smaller increments simplifies things. On a stock Contax lens, you can carefully set the aperture between two stops to get a half-stop, but it’s not going to stay there if you bump it. For personal shoots, it’s an option. I wouldn’t recommend depending on that for a client shoot. One evening I was feeling adventurous, and opened up my 50mm to took out the ball-bearing to de-click it. This made the iris click-less, but the aperture was loose and had no friction at all. I wouldn’t recommend doing the de-click yourself, unless you know how to add the right kind of lens grease to provide that “stiction” feel. I had Duclos de-click my lenses, and love the feel of the iris now. It’s smooth, it has friction, and I have unlimited control over the exposure range now. Highly recommend you do the de-click.

With the stock Contax mount, you can use a simple adapter to get them onto your camera system. Cameras like the FS100, FS700, and NEX-5/7 have good options…there are a number of Contax-to-NEX mount adapters that mount to the Sony e-mount, and then you simply put the Contax lenses on that. Easy. For Canon DSLRs, the C300, or RED Canon mount, you can put adapter rings on the lenses, if you aren’t interested in modding them like I did for the Canon mount. The adapter rings that I’ve used mount onto the Contax mount, and then the lens (with attached adapter) can be used directly on a Canon mount camera. This is fine for small, low key shoots where you aren’t using a follow focus. But I’d strongly recommend against using them on a camera setup where you’ll be using a follow focus…there is a risk that when you torque the lens, it could pop off the clip, or rotate. This is an annoyance, and potentially risky for the lens. It’s not good for a professional application, in my opinion. So, after shooting with the stock lenses and adapters for a short while, I decided that I really wanted a permanent Canon mount on the lenses. Leitax offers a mount replacement, which I’m told can be installed by a careful user. I chose to have my Leitax mount swaps done by Duclos while they were also getting cine-modded. Now that they have a permanent Canon mount, they go directly onto any mechanical Canon mount, no fuss and no adapters.

As part of my cine-mod, I had common front elements put on my lenses. So they all now have a standard 80mm exterior (which goes directly into many matteboxes), and 77mm interior filter threads (which is a very common thread size). This makes it very easy to change lenses when shooting with a mattebox, and avoids using step rings. If you want to do a DIY version of this, you can buy the appropriate step rings for each lens and build them up to the size you want. There is also a company called Cordvision that makes common step ring kits for Contax lenses, these are relatively cheap and a good way to accomplish this if you aren’t interested in doing the Duclos Cine-mod. In any case, I would recommend a common front element, it greatly simplifies things when shooting in the field. Simple is better…it means that you don’t have to reconfigure your rig every time you change a lens.

Filter Thread Table
The size of the front element/filter threads of Contax lenses vary based on the lens. Here’s a list of filter thread sizes that fit these prime lenses. Some Contax lenses are not listed because I don’t have that info or I’m not certain of the filter spec:

18/4.0 – 67mm
21/2.8 – 82mm
25/2.8 – 55mm
28/2.0 – 55mm
28/2.8 – 55mm
35/1.4 – 67mm
35/2.8 – 55mm
45/2.8 – 55mm
50/1.4 – 55mm
50/1.7 – 55mm
85/1.4 – 67mm
85/2.8 – 55mm
100/2.0 – 67mm
100/2.8 – 67mm
135/2.8 – 55mm
135/2.0 – 72mm
180/2.8 – 72mm
300/4.0 – 82mm

Next up, in Part III of this review I’ll discuss the flare characteristics and image aesthetic of these lenses. Stay tuned.


12 Responses to “Zeiss Contax Lenses – Part II: Resolution and Physical Characteristics”  

  1. 1 Craig Marshall

    I had pretty much come to the same conclusion myself and started building up a small collection of Zeiss Primes for my NEX series cameras so it was great to come across this excellent and carefully written article. Nice work Mathew! When can we expect part 111?

  2. 2 w b green

    I too have build a collection of these lens…and look forward to your 3rd part…I use them with a metabones on a fs700 and find they really give the Sony 35mm sensor a unique look

  3. 3 Craig Marshall

    Are you using the Metabones ‘speedbooster’ with your Zeiss lenses? I didn’t know they had produced it yet with the NEX-CY mount. I now have the Zeiss 50mm F1.7, 85mm F2.8, 135mm F2.8, 180mm F2.8, 300mm F4.0 primes plus the Mutar 2x Extender, all in C-Y mount. They make any NEX camera come alive.

  4. 4 w b green

    Yes I am using it. With the lenses ….I really like it….very nice getting close to the full frame image. I bought a. Heap extenter…seems work well….I have most of context lenders…missing the 35mm f1.4…I have the 2.8 model…so I will wait til I find a deal

  5. 5 w b green

    I just got the metabones last week…just happen to go to their site..the day it was released

  6. 6 w b green

    That is cheap extender….heap…ha ha

  7. 7 Craig Marshall

    I read that the faster, premium priced Zeiss SLR prime lenses were a ‘bit soft’ wide open so I opted for the F1.7 and F2.8 variants instead. I shoot 100% outdoors and here in Australia whee we have a monopoly on light! I found Sony’s own SEL 16-50mm F3.5 motor zoom lens is perfect for wide angle settings on any NEX camera so I only use my Zeiss primes for telephoto, ie: 50mm and beyond. At around $300 on-line, the SEL 16-50mm is a bargain.

  8. 8 Wilson Laidlaw

    I used these lenses for years on Contax RTS and RX cameras, which I believed was the finest manual focus 35mm SLR system made. However when Zeiss forgot to take any brave pills, had the hissy fit with Kyocera and limped out of the serious camera business with only one weak attempt (the ND) on serious digital, I jumped ship. I had been using Leica rangefinders since the late 1950′s and when they brought out the M8 went down that route, going on to an M9 and now the M240.

    With its live view and EVF as well as the optical rangefinder, I can now use a choice of SLR lenses. I bought in advance of the release of the M240, a couple of Leica R lenses but all the good ones are now being snapped up at ever increasing prices. There are a lot of very mediocre, Minolta built R lenses out there, which were not good in the 1990′s and have not improved since. The Kyocera built 80-200/f4 Vario Elmar is pretty good. However now that I have a modified Adriano Lolli Contax to Leica M adapter, which activates the R lens menu on the M240, I wonder if I should have bought the Vario Sonnar 80-200.

    I have bought the 28-85 Vario Sonnar, which I know from old is a great lens and I paid around 10% of what I would have had to pay for a Leica 28-90 Vario Elmarit. I have also bought a 300mm f4 Tele Tessar. This is a lens which I always feel takes better photos that the bald MTF and other figures would imply. It just renders beautifully. I picked up over the last two days a pair of Mutar 2X Extenders, a I and a II, at just plain silly give away prices. The postage from Japan to the UK is going to cost me almost as much as the Mutars (2 sellers unfortunately).

    The only other lens I would like to have is the 15mm CX/Y Distagon but the secret of these lenses seems to have got out and prices are pretty healthy. I have a 15mm Voigtlander Super Heliar M mount lens but this is a very poor performer on the M240. Strangely much worse than on the M9 and has horrible vignetting and red edges on the M240, which the internal camera lens correction seems to be doing little to improve. With the retrofocal design of the Distagon and its more telecentric nature, red edges should not be a problem. I know that my 16mm Zenitar fish-eye does not have the problem on the M240 and the exit pupil to sensor distance on this lens is about the same as the Distagon.

    Wilson

  9. 9 alan

    I have the 35/1.4, 50/1.4, and 85/1.4 with Speed Booster on my NEX-6 and FS100, and am very happy.

    I also have or have had 25/2.8, 28/2, 35/2.8, and 85/2.8. I very much like the latter two because they’re about 250 grams (like the 50/1.4). The others are a bit heavier and don’t handle quite as effortlessly and naturally for handheld shooting.

  10. 10 alan

    In my experience the German-made ones tend to have smoother and quieter rings. The earlier AE versions of the 85/1.4 and 35/1.4 both have “ninja star” apertures, which are kind of funky, but I chose them over the MM versions because mine are German made.

    I have also tried the much-praised 35-70/3.5, which is optically excellent. But I can’t deal with the combined push-pull zoom/focus mechanism. Maybe I just have bad coordination, but I prefer to have focus and zoom separate.

  11. 11 Wilson Laidlaw

    Alan,

    I know what you mean about the one touch zoom. Having been using one touch on the 28-85 Vario Sonnar and two touch on the 80-200 Vario Elmar, I have come to the conclusion that by a bit of good luck, I have got the correct configuration for a mid range and zoom telephoto. One touch would not, I think, be suitable for a zoom telephoto, as it is so critical not to move the focus as you zoom. With the mid range zoom, framing and focusing quickly is more important and if you are at say f5.6, you have enough focal latitude for a small amount of focus movement as you zoom.

    Correct adjustment of the Zeiss zoom lenses is very critical, so that they are parafocal i.e. that focus stays constant as you zoom. Zeiss were the first people to develop this and there are three adjusting screws on their CX/Y zoom lenses to get this right. However it is a real expert’s job to tweak this sufficiently accurately, as adjusting one screw tends to change the other two adjustments. Johnsons Photopia, who used to be the UK service agents for Contax, were notorious for being unable to get this anywhere near right.

    Wilson

  12. 12 Wilson Laidlaw

    Alan,

    A lot of the German made AE lenses are getting old now. Also, an undisclosed (I took someone from Contax UK for a long lunch to try and persuade him to “spill the beans” but failed) number of the lenses had minor optical updates from AE to MM and certainly the formula of the T* coating was improved. Thus although as you say, some of the German made lenses have a better mechanical feel and especially tighter fitting bayonets, they may be slightly optically inferior. Two which I believe were not updated, the 18/4 and 25/2.8 Distagons, were beginning to feel their age by the end of the MM manufacture.

    Wilson