Click for text version
Magnus Wedberg / home

Sony/Minolta 135/2.8 [T4.5] STF
For those with short attention span
Sample pictures are located at the very bottom.

Preface
Hi there. If you are here, chances are that you are interested in the 135/2.8 [T4.5) Smooth Trans Focus lens made by Minolta (but nowadays available under the Sony name, as Sony bought Minolta's camera division). It is manual focus only, but is used in the standard Minolta AF/Sony Alpha bayonet. This lens is made specifically to produce pictures with good bokeh. If you don't want to read up on bokeh in the previous link, bokeh is the name for the rendition of unsharp areas in the picture. Good bokeh is smooth transitions between sharp and unsharp areas; bad bokeh is lines being doubled when unsharp, highlights hexagon-shaped or donut-shaped, etcetera.

Firstly, allow me to stress that the STF lens is not a soft-focus lens. Soft focus gives a dreamy, creamy, somewhat eerie feeling to an image by (using a simplified description) overlaying the sharp image with an unsharp one using controlled aberrations of the lens; the STF lens produces perfectly sharp pictures, it's just that unsharp areas are optimized for the best quality possible. Minolta also made a traditional soft focus 100/2.8 lens, not carried over to the Sony lineup. Each has its own use, although one may argue that with digital photography, one can simulate soft focus effects from a sharp image in the computer -- while the bokeh of the STF lens is impossible to add in post-processing.

All example photos are taken with the STF lens mounted on a Dynax 9, on Fuji Provia 100F color slide film and Ilford Delta 400 Professional B/W film. They are scanned on a Minolta Dimâge Scan Dual using Vuescan software. The small pictures are resized and lazily auto-sharpened in IrfanView; the larger-sized pictures you get to when you click on those pictures are resized and manually sharpened in Photoshop. The pictures inside the text may be taken with anything. It's indicated where needed.

Let's begin!

The build quality
I am a privileged guy -- I have access to an array of Minolta lenses, and some of them are of the highest quality. With the 300/2.8, 200/2.8 and old style 85/1.4 all metal construction in my greedy little hands, I thought Minolta could never produce a better mechanical construction. Man, was I wrong. The pictures of this lens one can find on the web gives the impression that this is a polycarbonate construction. It is not. It's all metal, and VERY rugged. It's painted with a black variant of the paint the white G lenses use. The silvery parts are metal, too. With a weight of 730g, it's considerably heavier than the 85/1.4, almost as heavy as the 200/2.8!

This lens gives, without any doubt, the highest impression of mechanical quality I have ever seen in a Minolta lens.

The optical construction
"Construction: 8 elements, 6 groups (including 1 apodization filter)" according to the specs. Now, what is an "apodization filter"? David Kilpatrick answers on the Minolta Mailing List:

To: <Minolta@yahoogroups.com>
From: David Kilpatrick <iconmags at btconnect dot com>
Date: Thu, 14 Feb 2002 11:37:31 +0000
Subject: Re: AW: [Minolta] Re: Just received the 135/2.8 STF lens

It has a centre graduated filter in the middle of the lens next to the iris. Clear in the middle, darker to the edges. It is not a coated or dyed filter, but is actually shaped (negative) lens element. By making the lens element out of grey tinted glass, the thicker edges of the minus lens are denser than the thin middle bit. Simple idea, quite brilliant. It means that wide apertures have a graded edge to the iris shape, instead of a clean circle, but small apertures are not affected and there is less speed loss. It looks a bit like a 'centre filter' as sold for Super Angulon wide angle lenses.

I supposed someone must have ordered a pair of -3 dioptre Ray Bans and noticed that they are clearer in the centre than at the edge!

Minolta owns a huge number of really strange and exotic patents, including many acquired or bought from inventors and photographers. A guy in New Zealand sold them an entire greyscale zone system metering patent for viewfinder displays, not yet used.

The STF might be their own, it might be one they were offered. It is certainly unique. I am not sure if the whole graded effect is achieved by glass thickness though (this is what they told me).

David Kilpatrick

The apodization filter can be thought of as a radially graduated ND filter in the optical path. Because of this, the "filter" is always there, regardless of setting on the lens. "Of course", you may say, but I was not sure of this before.

Why did I thought that the filter was optional?

Well, this lens has two apertures. In manual aperture control mode, it's a 10-blade aperture with rounded sides. In A (auto) mode it's Minolta's "standard" 9-blade aperture with rounded sides. By the way, why this is so is totally beyond me; why not have just one, the 10-blade aperture? Anyway, it was my hope that this "apodization filter" could be removed by some trickery in A mode, effectively giving the lens a 2.8 max aperture (but not as good bokeh). That is obviously impossible, as it is a lens element, an integral part of the lens design and it always sits there stealing 1.5 stops of light. Thus the lens is limited to being a 4.5 lens in light transmission, but naturally with a 2.8 depth of field! Thus the 2.8 [T4.5] designation.

The lens has two main working areas on its aperture ring, "A" (automatic control of the aperture) and manual stepless (well, click stops are there, but you can use settings in between, of course) aperture control between T4.5 and T6.7. I would have liked it better with no A mode and a manual aperture ring all the way between 4.5 and 22, but it's no big deal.

The lens is really fat in appearance. The old 135/2.8 was pretty a discrete lens, but this baby is right-out intimidating. That keeps me wondering what this lens would actually have been if the apodization filter hadn't been incorporated and Minolta had set out to make a good traditional 135 lens. A 135/2.0 at the same price as this lens would have been really nice! Nikon offers a 135/2.0 DC (Defocusing Control) aimed at the same kind of buyer at a slightly higher price point ($200 more as of writing this 2002) and I would love to do a side-by-side comparison. The Nikon can AF, too, but can not give the supreme bokeh of the STF lens -- the DC lens shifts lenses around to over- or undercorrect for spherical aberrations, allowing you to choose if the background or foreground unsharpness should be optimized, while the apodization filter in the Minolta lens optimizes both foreground and background.

By the way, Sony have recently announced an autofocusing Carl Zeiss 135/1.8 in Minolta A mount (now the "Sony Alpha mount"). Available in fall 2006, this is one of the most exotic lenses ever released in Minolta mount, and the existence of two specialized, very expensive 135mm lenses in the lineup says... something. :-) Either that Sony wants to offer this focal length for a future full 35mm-sized sensor or that they recognize the need for a fast 200mm (equiv.) for the current APS-C sized sensor. Or both. Anyway, I would like to do a comparison, but the price is prohibitive and Zeiss are traditionally known for heartbreakingly bad bokeh. Oh well. Update, update: the Zeiss has been released and test shots have shown up on the web, and surprise surprise, it has good bokeh. Not STF-good in the least, but still very good, comparable to or better than many good classic Minolta lenses. The general properties of this newer lens (overall image quality, autofocus ability, and speed) together with the surprisingly modest price means that the 135/STF is reduced to even more of an exotic... if at all possible. Only extreme hardcore bokeh fans will see a need for the STF lens. Then again, I ain't switching!

Focusing
The focusing ring is wide, with a rubber grip area. Focusing is manual only, and the camera does not attempt to use its focusing motor even if in AF mode. The AF indicator does not work at all, however, but that does not matter because focusing in the viewfinder is extremely nice. You can very easily see the "micro focus" differences, just a fraction of a millimeter's turn will render the detail sharp or unsharp. Truly very nice! I have even had photographing friends spontaneously comment on how nice it is to focus on the 9. The focusing ring is not oil-damped as old style MF lenses, it just moves with the natural resistance from the groups of heavy glass, and although the movement of the ring is very smooth it's here the lens exhibits one of it's major flaws -- focus creep. When pointed down it's OK, the focus stays where it is even if just a easy touch will alter the focus towards minimum focusing distance (0.87m). When pointing the lens up, on the other hand, the focus will move by itself towards infinity. This is very frustrating, sometimes having to fight with the focusing ring instead of concentrating on the picture. Why didn't they put in some kind of focus brake? Unbelievable.

Using TC:s
The lens is one of the select few that can be used with the Minolta's matched APO converters. This, while being nice on principle, is of no practical value -- a 189/6.3 (with 1.4x TC) or 270/9 (with 2x TC) isn't all that sexy.

The hood
...is large and seems nice overall. It is lined with a very thin velvet material of some kind, not just made of frosted plastic as the other Minolta hoods I have. I wish Minolta would have made it a tulip shaped hood, but it's not. It can be used on the 85/1.4 without vignetting although it is much longer than the original 85 hood.

Other random points
The front, with 72mm threads, does not rotate during focus. That is good, but I would have been an even happier camper if the lens was compatible with Minolta's internal filter system and thus their excellent internal polarizer.

Optical performance
Sharpness
Very good. Sharpness seems to be excellent both in the center and the corners. I haven't actually made enlargements, though, so you have to take this with a grain of salt; I have just checked the negatives with a loupe and looked at the scans. But from the look of this, I would definitely say that this lens is on par with the G glass I own.

Vignetting
Nope. None. Zilch.

Distorsion
Yes, I have taken photos of a brick wall, mostly just for the hell of it. No, I won't scan and publish it here. Suffice to say that the lens has no noticeable distorsion at all.

Bokeh
You kidding? Look at the pictures! ;-) Seriously, it beats (and quite easily, too!) my 85/1.4, my previous "bokeh champ". Below is a picture I took a couple of years ago with my 85, as comparison...

My opinion
Why I bought this lens? I was curious. I wanted the bokeh. I wanted to trig myself to take more portraits. Heck, I wanted to trig myself to take more PHOTOS. And it only costed me $547, including shipping, new in box from www.scandinavianphoto.se -- so I figured it might be worth it just to satisfy the itch known as the Gear Acquisation Syndrome...

Now, would I recommend it to others?
In a word: no. Not because of any lack of quality, because it's an outstanding lens, clearly peerless for portrait use. But it's also an odd bird. Most people would be better off buying the likewise excellent 85/1.4 and add a Kenko Pro300 1.4X tele converter for some extra reach. That is a much more versatile setup, even if the optical quality with the converter will be lower. However, if you like extreme mechanical precision, great sharpness, fantastic bokeh, and smooth manual focusing -- yes, you will definitely like this lens. You will probably not like the weight, price, slow maximum aperture, and the focus creep however. You may not like the lens on the Dynax 7 Digital, either, as it transforms into the equivalent of a 202/4.5. A superlative 202/4.5 for sure, but huge, and 202mm is not a very good focal length for portraits. On the other hand, Keven Fedirko has this to say regarding the utility of a 200mm portrait lens:

To: <mw at 9000 dot org>
From: Keven Fedirko <kfedirko at telus dot net>
Date: Sat, 14 May 2005 17:24:43 -0700
Subject: Re: A few more night pictures

I love my 200/2.8 for head portraits outside - awesome at 2.8, and the extra reach makes the subjects relaxed. I wouldn't have figured it would be good for that, but it _was_ listed in M's lens brochure in the portrait lens section years ago - and it got me thinking... It was one of the reasons I ended up buying it.

k.
--

- altered perceptions . http://www.kevenfedirko.com/

So, is it worth the money?
For the kind I paid for it: yes, absolutely. At street price? Only you can decide, but personally I think it is way too expensive for a lens of very limited utility.

Speaking of bokeh
If you want a real exotic portrait lens and think the 135/STF is too mainstream, try the 85/1.4 Limited Edition; it is a slightly modified version of the standard 85/1.4, with reengineered (and thus larger and heavier) front element. It does not feature STF technology, but bokeh is notably improved over the already very good standard 85, while keeping the bright f/1.4 aperture.

It might be a little hard to find, though: only 700 lenses were manufactured, and they were only sold in Japan. A worthy object to hunt for! Looking at pictures from this lens, it is absolutely outstanding. I am told this was the original design for the 85/1.4, but that it was dropped in favour of the somewhat lighter, cheaper 85/1.4 we all know and love. That is certainly no bad lens, either.

Other resources
For more test shots, see cameraunion.net's great overview -- it's in chinese, but the images speak for themselves. Of special interest is the optical diagram showing the tinted element and the shot showing perfect geometry (no distorsion).
This comparison by J Greely, comparing the original (now since long discontinued) Minolta 135/2.8 with the STF version may also be of interest, but do notice that he unfortunately did misinterpret the settings on the lenses. The STF lens at 4.5 should be compared with a traditional 135 lens at 2.8 -- the STF lens is 2.8 at its 4.5 setting, it's just that the light transmission is lower due to the tinted element in the optical path. J's direct comparisons are thus invalid (a 135/2.8 wide open would not produce hexagonal highlights), but may be interesting anyway.

Assorted imagery


photos articles services about