Review: Tamron SP 350mm f/5.6 Model 06B (Adaptall-2 System)

(2010-02-18)

 

A fellow photographer on www.fotostart.dk has encouraged me to write a review of my (relatively rare) catadioptric mirror tele lens. It is with some hesitation that I take up this challenge, (my first gadget revie ever) because although I've photographed since I was 11 (and here we write 1960) I am not what one might call an experienced and competent photographer

 

And when one - as an amateur without “unbiased” high-tech test gear - reviews a lens, there is certainly always the risk that one cannot give that lens its right’s deserve: Because one will by necessity have to use a specific camera and above all one’s own abilities – or lack of same - as a photographer to demonstrate the properties of that lens. Furthermore, although I have photographed digitally since 1999 I have only photographed with DSLR since April 2009.

 

Anyway, now I have taken a deep breath and plunge into my subject by displaying an image right away:



 

Two things immediately jump into one’s eyes: 1) The limited depth of field - lens cannot be stopped down and 2) the very special bokeh. There are many who would vigorously refuse to touch a lens that might show such a bokeh in any situation and they may then leave at this point. If there are anyone left, here comes a little more

 

A bit of background for the lens (hereinafter simply called the 06B).

Model 06B was produced only during a limited number of years, from 1981 to 1985, unlike its bigger brothers, Models 55B and 55BB, SP 500 mm f / 8 which were produced from 1979 to 1983 (55B) and from 1984 until 2006 (55BB).

 

The lens is of the Adptall-2 SP (Super Performance ") series and requires a special adapter ring for different camera brands. The Adaptall-2 system is fairly widespread, and adapters for most brands are easily found on the internet for such lens mount types that were in use up to the early 2000’nds. If you have a newer camera with a mounting you may resort to a standard M42 Adaptall-2 mount plus an M42 adapter for your specific camera – that way, you should be able to get a suitable match after all.

 

The focal length of 350 mm was not randomly chosen: In fact, this is very much the shortest focal length that a compact mirror lens may have, should the light fall-off towards the edges (vignetting - inevitable for this type of lenses) be kept to an acceptable minimum for a 35 mm film format, or a full-frame sensor in current times. When the 06B lens was released, it had a list price of 48,400 yen while the 55BB had a list price of 59,000 yen. This is actually a little surprising: As most amateur astronomers will know a "fast" mirror telescope (from about f / 5 or less) requires significantly higher standards of accuracy in the manufacturing and alignment techniques than a "slow" telescope (from around f/10 and up). One might speculate that the actual price differentiation was dictated by market considerations (?)

Anyway, the limited product lifetime of the 06B indicates that it did not really respond to market needs in those days. Maybe, people who bought this type of optics were mostly after a real "moon lens" or, perhaps the manufacturing costs of the 06B (in an acceptable quality after Tamron’s own standards) turned out to be too high for the price the market would bear for a fixed aperture telephoto lens in the 300mm range?

 

A bit about my own 06B, s/n 110231

In 1981 I bought a small astronomical mirror telescope (a Vixen 4 " f/10 Newtonian Polaris R-100L), and with that came the desire for astrophotography. Next investment then, was then a Pentax K1000 that same year, as my old Porst Reflex S was completely worn out. I soon discovered that I had better use my Newtonian telescope as a guide telescope and acquire a shorter telephoto lens which could ride (‘piggyback’) on the back of the telescope. A mirror telephoto lens - simple, robust and relatively cheap - seemed just the thing, and I had just seen such on offer where I bought my K1000. The 55BB and 06B (and the refractor type Model 54B, SP 300mm f/5.6) cost almost the same except for a few scores of EUROs. I pondered quite a bit for quite some time about whether it should be one or the other, but I finally resolved that the 06B together with a Tamron SP teleconverter Model 01F and my Vixen telescope would provide appropriate focal length steps of 350mm - 700 mm - 1000 mm and with that I could cover a little bit of everything.

 

And so it happened that I became the owner of a lens that was somewhat overlooked in its days, which has therefore become somewhat of a rarity and which today - in some circles - has achieved almost mythical or cult status. (Be prepared: All things considered, it is not THAT good!).

 

I got out of the store with those purchases along with a Tamron Wide Field Tele-View Adapter, Model 02F which is a 20 mm right angle eyepiece that allows me to use the lens as a spotting scope also. The whole package – if I remember correctly - cost me a good 400 EURO – but remember, that was in good solid 1982 currency.

 

As said, I bought this lens with astrophotography in mind and I still mostly use it for that; so, for a start, here are just a few samples (full, un-cropped images):



Lunar eclipse on 31 December 2010


Sunset in 1986 (quick-and-dirty digital camera duplication of a Kodachrome slide


 

- no more about astrophotography in this review! In fact, I have kind of discovered that the digital camera age offers better usage (for me at least) of this special lens in a number of other areas.


Specifikations and Design:
 

Basically, a mirror telephoto lens (a catadioptric lens or just “CAT”, as we say in astronomy circles) consists of a convex main mirror that captures and focuses the light and a concave secondary mirror, which "breaks" the beams and sends the light back towards a hole in the main mirror and into the camera. In practice, there is also a large, aspheric corrective front lens and a few other rear lens elements to make the design work in a photographic context. The designa and specifications for the 06B, 01F and 02F are shown in the tables and schematics below.

 

 

TAMRON Wide Field Tele-View Adapter, Model 02F

Specifications

Focal length

20mm

 

Exit pupil

(f/2.8) 7.1mm

(f/8) 2.5mm

Field of view (@ 1,000m)

(10X) 126 m

(25X) 50 m

Angle of view

(10X) 7.2o

(25X) 2.9o

Design

5 elements + roof prism

Maximum length

61mm

Maximum height

106mm

Weight

257 grams

 



And here are some pictures that show what the system actually looks like:



All parts:



Lens and Camera:


Lens back:


All parts joined as spotting scope:

 

Note the large central obstruction, which is base for the secondary mirror. In the 06B this obstruction is about 4 cm in diameter out of the total aperture diameter of 82 mm. This IS a lot, and much of what you read about problems with mirror lenses in general (peculiar bokeh, focus difficulties, sharpness, contrast) can be traced back to this design.

 

"Test Set-up":

I regularly assess my telescopes, lenses and cameras on a "test bench", which consists of an office building around 3-400 meters away and a steeple about 1 km away. For today’s tests, I have expanded this “test-bench” with a primitive setting for testing the sharpness and contrast at the minimum focusing distance of 110 cm in the form of: perspective drawing paper, a small ruler and a stamp, as shown below:





 

Before we get to my "test" images and the rest of the pictures in this review, just a few general observations:

 

Resolving Power: The theoretical resolving power of a lens depends only on the absolute/effective, physical size of the aperture opening. For 06B this is about 2 arc seconds. A beam with this space angle will form a spot in the focal plane of 0.0033 mm with 350 mm focal length and just under 0.007 mm at 700 mm focal length. One DSLR pixel element is typically around 0.006 mm in linear dimension and therefore, it gives no sense to discuss resolving power of such a lens based upon a DSLR image that may typically only resolve some 75 lines per mm.

 

Contrast: On the other hand, it makes good sense to assess to which degree the camera + lens combination can distinguish between different shades of gray. In this aspect, it makes sense to compare different lenses using one and the same camera.

 

Focus, distortion, sharpness, saturation: For the serious camera brands, all CCD- and CMOS sensors come from a handful of highly qualified manufacturers. These sensors come with very similar specifications and quality within each sensor size/pixel number class. Poor lens quality will always show up regardless of the choice of (quality) camera brand. But there may be other, visible differences that can be attributed to each camera manufacturer’s use of imaging processing “engines” inside or outside the camera (e.g. in their RAW-conversion software).

 

Camera Settings: When you shoot in RAW, you obviously must make a choice in regards of settings for contrast, sharpness in the conversion to JPEG. (If you don’t, you still do: You just rely on the manufacturer’s choice of standard settings). When one, like me, frequently just shoots in JPEG, one must also take into account the in-camera settings for the conversion that takes place in the camera “conversion engine”. I prefer to shoot in the "soft end" of the scale - no "bright" or "vivid" colors and no aggressive settings of contrast and sharpness for me thanks! I can always adjust and correct for "soft" settings and add a little sharpness, contrast or saturation in post-processing. But it is impossible to go the other way (e.g. from ”too contrast” to ”more normal”) and still retain all the detail that would have been in an original “softer” image. All mirror lenses produce in all but the very best lightning conditions somewhat weaker contrast than conventional lenses do and they are – as all long-focal tele lenses – very sensitive to the slightest haze in the air. In the old analogue days you had to take this into account in the choice of film type and the development/printing in the wet darkroom. Now, you must do the same in your choice of camera default settings and / or post-processing. (And THAT has made things much easier today!!!).

 

And now it is time for some "test" shots. The images shown were taken with a Pentax K200D and most images are with hand-held camera:


06B, 350 mm:






06B, 700 mm:







06B, 350 and 700 mm (100% crop):



 

From these results and others I will allow myself to conclude:

 

Sharpness: Yes, the lens is sharp, both with and without the teleconverter down to the minimum focus distance of 110 cm, where one obtains a reproduction ratio of 1:25 respectively 1:1.25.

 

Focus: Those who claim that 06B cannot take sharp pictures are wrong. BUT, I admit that the beast can be hard to focus and today's smaller and darker viewfinders have not made life easier in this respect. What makes this lens tough to focus is the fact that images are formed from the parts of the light bundles coming through the outer parts of the front lens. Thus one turns the focusing ring quite a lot to reach the proper distance and then – just a tiny, tiny change will make a lot of a difference as to how sharp the image will be. And regarding the dim finder view: In low light there is only one thing to do. And that is to Shoot, check, fine adjust, shoot, check.... Even under good lightning conditions it can be frustrating until you have achieved a certain exercise (and you should still expect quite a few misses); a right angle viewfinder with 2X magnification can be very helpful for tripod-based shots.

 

Distortion: For all practical purposes – there is nothing to see or measure.

 

And the notorious bokeh? Well, that one has to live with. Some claim that they actually like it and exploit it artistically. Personally, I'm not crazy about it - to say the least - and always try to compose myself out of the situation by selecting scenes and shooting angles where the subject is well separated from the background.

 

However, there is another problem with mirror lenses, namely

 

Hotspot: As mentioned, Tamron designers of that time put a great effort in minimizing the decrease in brightness towards the image edges. But the effect (vignetting) is still there, and to illustrate this I have taken a picture of an ordinary piece of patterned paper in normal, ambient room lightning conditions (i.e. without flash):



 

We see that the lens + camera combination nicely captures the weak lines and even the imprint of lines on the back of the paper, something I could never see with the naked eye. But when I enhance the contrast for a better view of the lines, the hotspot effect is evident. This effect is seen when one takes pictures of large, uniformly lit surfaces such as the sky, but the effect has largely disappeared at 700mm focal length, where the entire sensor is apparently located inside the hotspot. In the old days of analogue film, there was virtually nothing to do, and it could be very annoying at times. Today one fortunately has software, designed to remove vignetting, that can compensate for this effect, as the following example shows:




 

And let's just have a look at this scene in full view

 

With Tamron 18-200 mm zoom at 35 mm


06B, 350 mm


With 06B, 350 mm - (100% crop)

 

- Handheld on a gray February day in 2010; I guess that’s quite OK?

 

What then, may you use this lens for?

As said, for me it was astro photography (and budget) that drove my choice in 1982. Of course, one of the contemporary Tamron 300 mm f/2.8 lenses (there were two models released, one just after the other) are both faster and provide better images but they also cost just below and just above 300,000 yen - and then they both had a weight around 2.1 kg, while my 06B only weighs 577 g.

 

Portability and the possibility for handheld, long-focus telephoto shooting were by no means granted sake then. Today we can change ISO with a simple finger flick; we have image stabilization (for those of us who are fortunate to have the stabilization in the camera body!); and modern construction materials have made all lenses much more lightweight. But I would still argue that the compact size and moderate weight make 06B a good companion on the days where you just want to take a stroll and shoot with long focal length as opportunities now presents themselves. For me, the ability to switch ISO and image stabilization in the digital age have given this modest lens a second youth; I have started using it for other things than astrophotography, and I started practicing how to achieve decent focus...

 

The Macro Capability by virtue of the modest, minimum focusing distance (1:2.5 or 1:1.25 at 110 cm) has always been as a big plus to me. Admitted, I do not photograph stamps with it, but what about a hornets’ nest? Or the elusive butterflies? Or insects in flight?

 

Another example is that a couple of wrens had built their nest just above the door to our patio at the cottage in the summer of 2009. When we arrived for the summer, the couple was busy feeding their young ones, and I obviously had to photograph that.

 

  • Problem (1): The wren is the second smallest bird around where I live. Not exactly humming bird sized, but it IS very small. So, even with 700 mm focal length, I had to come close to their nest (2-3 meters).

  • Problem (2): The nest was in the deep shade under the eaves - and wrens are VERY fast flyers for such small a bird.

  • Problem (3): The birds refused to fly to and from the nest if we were closer than 5-6 meters.

Here modern technique once again came to rescue: Camera up on a tripod in the right distance, ISO up to 1600 to get a decent exposure time (in the rather deep shade) and then a radio-controlled shutter release. With this, I could stand in respectful distance and shoot when the birds sat at the entrance to the nest. The results we see here (again, as full, un-cropped images):



06B, 350 mm (Pentax *ist DL)



06B, 700 mm (Pentax *ist DL)



06B, 700 mm (Pentax *ist DL)

 

Sample Images:

Let me conclude with a few more or less processed images. Others have taken better pictures with this lens, but these are my own.

 
















Conclusion:

Is this a lens that I think about to part with? - NO WAY! It is not the perfect telephoto lens by any standard. Focus IS difficult (but practice makes master) and the bokeh IS very special. It is fairly slow, DOF and versatility is limited due to the fixed aperture of f/5.6.

 

But it is fun to use, it is extremely compact and easy to carry (almost) everywhere and it can certainly deliver better results than I have been able to show here. I shall continue to exert myself in getting the most out of this lens in the digital ages.

 

Is it a lens that I may confidently and unreservedly recommend to everybody? - No, only if you make the restrictions clear in advance and have a very good idea of what you will use it for, how and why; (well…. of course there's also always the collector’s gene lurking in many of us).

 

What should one be willing to pay? - Difficult questions. I have seen it go for around 300 and up to 500 USD in 2008; around GBP 150 in 2009 and in late 2009 I saw a copy offered for EUR 295. It is probably a matter of luck or lack of the same - especially if there are multiple bidders, bidding each other up. Anyway, because it has become a collector’s item, you must unfortunately be prepared to pay some “overheads” to that account

 

Literature:

  • Comprehensive information on Tamron lenses, and additional links (of which some are however obsolete and broken):

http://www.adaptall-2.org/lenses/06B.html

  • Interesting discussion for-and-against-mirror lenses in the digital age with some good example pictures (though none with the 06B):

http://photo.net/nature-photography-forum/00IdpJ
 

View: Sample Images Slideshow

 

Brochure: Tamron SP 350mm f/5.6 Model 06B

Manual: Tamron-SP 350mm f/5.6 and 500mm f/8 CF Tele Macro Catadioptric Lens Owner's Manual

 

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