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10-15-2010, 11:17 AM   #31
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QuoteOriginally posted by Lowell Goudge Quote
I really should do a similar comparison shouldn't I
QuoteOriginally posted by stevebrot Quote
Now that sounds like a lot of fun.

Steve, that is the subject I think of a meet up, with local forum members. It would be very interesting to have a Focal length shoot out, with each member bringing what ever options he/she has for the day.

The big problem with lens threads on the forum is no two people are capable of taking the same shots, and no one menber has a significant number of lenses at each focal length.

I may be a bit of an anomaly here, with an M42 kit from 24-200 mm, and a K/KA mount kit from 8 - 400 mm (with a gap between 135 and 300mm nicely filled by my series 1 70-210 F3.5 version 1)

but even I only have at best 4 lenses (not counting my AF zooms) at any one focal length, but in most cases just 1 or 2, and therefore real head to head is difficult.

10-15-2010, 04:56 PM   #32
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QuoteOriginally posted by RioRico Quote
That was the problem with my Tamron 28/2.5. I slid off the knurled rubber focus ring and found that two grub screws were loose and one was missing. Tending to the screws fixed the loose-focus problem.
_ _ _ _ _ _ _ _ _ _

And I should have said to Steve: GREAT COMPARISON! And thanks for the pointer on the Access 28. EDIT: I just searched that thread and found nothing about the Access 28. Bother...
Damn! I could have sworn that the Access lens was discussed on that thread! May be it was on the "Dirt Cheap" thread...

07-06-2013, 10:42 AM   #33
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Note: The original posting for this thread included multiple images hosted on my Pentax Forums albums. At some point and for some unknown reason, the image links were stripped from the text. The photos are still there and can be viewed at:

stevebrot's Album: Lens/Camera Tests -


QuoteOriginally posted by stevebrot Quote
The various versions of the Vivitar 28mm have taken on sort of a cult status on the Pentax Forums. This is particularly true of the K-mount close focus versions made by Komine (catalogued as K01, K02, K06, A01, A02 by Robin Parmar...see Photografica). Incredible photos by jsherman999, igilligan, and others started to surface showing excellent sharpness and contrast as well as wonderfully clear and vibrant colors. In the depths of my dark inner LBA, the small voice said, "You've got to get yourself one of those". The notion was really sort of absurd. I already had a Tamron 28mm that I had owned for years and used extensively on 35mm film, but seldom mated to the K10D. I also have the FA 35/2 as a walk-around "normal". Still the temptation incubated and festered until I made the mistake of posting an interest in acquiring a K02. Within a few hours, there was an offer from a fellow forum member who was upgrading to the A01 and a few days later the lens was on its way to my house.

Initial Impressions (Size, Build, etc.)
When the lens arrived, I was pleasantly surprised at how compact and light it was. I had always considered my Tamron 28/2.5 to be small for a 28mm, but the Viv is darn-right petite by comparison. It was about this time when I thought it might be interesting to do a comparison test between the two lenses. After all, both were made about the same time and I had bought the Tamron over the Viv "back in the day". (The Tamron was more expensive at $79 + $17 for the adapter vs. about $59 for a Viv, but could be used with multiple bodies.) I had enjoyed the Tammy for many years on film and always considered its performance to be top class. Did I make the wrong decision 25 years ago?

Setting the two lenses side by side, it is hard to believe that they do basically the same thing. The Vivitar is physically both shorter and smaller around with a fairly large front element to support its f/2.8 maximum aperture. The Tamron, on the other hand, has a fairly small, almost hemispherical, front element set in a squat, flat-faced barrel. I always considered the Tammy to be handsome, but sort of odd looking. Handling the two lenses, the differences are even more obvious. Although the Vivitar has a minimum of plastic parts, the Tamron is all metal and significantly heavier. Focus and aperture controls on the Vivitar are about par for third-party lenses of the day. The focus is smooth and well-dampened. The aperture ring on my copy is rather stiff with indistinct detents. This may be correctable with a little disassembly and cleaning. The Tamron is also well-made, but the build is definitely a notch or two higher on the scale. All controls operate as well or better than the K and M series Pentax lenses of the same era.

In regards to focus, one of the features of the Vivitar is "Close Focus" capabilities. The lens will attain closest focus at 23cm after about 240 degrees of movement. This yields a magnification of 1:5. The is nowhere near macro, but still very impressive for wide-angle of the time. Interestingly, the Tamron is no slouch in this area either. It focuses down to 25cm. Unfortunately, as we shall see below, this is accomplished in only 120 degrees of arc. The focus direction of both lenses is opposite that of Pentax.

Another difference between the two lenses is the number of aperture blades. The Vivitar has 6 blades as opposed to the Tamron's five. In theory, the Vivitar may have a more pleasant rendering of specular highlights as a result.

While the Vivitar is really nice, I have to give the Tamron the edge in terms of build and physical design.

A lot was happening in the early 1980s in 28mm lens design. 35mm SLRs were incredibly popular and many people were interested in getting a good lens for general landscape photography. The relevant features were a relatively fast maximum aperture for easy focus, sharpness, minimal barrel distortion, resistence to flair and coma, and moderate price. The strong points for the Tamron were the BBAR coatings, low distortion and above average sharpness across the field. The Tamron has 7 elements in 7 groups and is able to stop down to f/32 (!) for maximum DOF. Minimum focus distance is 25cm. For a full description of the Tamron 28/2.5 02B including optical diagrams, see: Tamron Adaptall-2 28mm F/2.5 Model 02B.

The Vivitar was also well-regarded and was considered to offer above average performance. Available documentation for the non-CF versions indicate 7 elements in 7 groups, though it is not clear whether that design is shared with the CF version. If anyone knows of an online source for the specifics of the K02 design, please post a comment!

The Contest
As noted above, there has been a lot of discussion about the Vivitar 28mm lenses as well as many test shots indicating excellent performance. On the other hand, there is very little about the Tamron beyond a few user reviews ( Third-Party Pentax Lens Review Database - Adaptall-2 02B 28mm F2.5). My purpose here is to compare and contrast the two lenses under controlled conditions. While I have not included the results, I did do a "cereal box" test for sharpness/contrast at 20x the focal length for both lenses at f/2.8, f/5.6, and f/11. The results were amazingly similar for both lenses at all apertures with a slight edge going to the Vivitar. The most valuable information from that test was realizing that the Tamron is incredibly difficult to fine focus. Typical of many wide-angle lenses, the Tammy has a very short focus throw, making critical focus at moderate distances a royal pain. The Vivitar, on the other hand, negotiates almost a full turn lock-to-lock...luxurious! So, without further discussion, here are a few comparison images...

All images were taken with a Pentax K10D equiped with a Katzeye after-market focus screen. Manual exposure was used with settings supplied by a Gossen Luna Lux hand-held meter measuring incident light. All images were shot in RAW and converted using Lightroom with the default development settings. Brightness was adjusted for some images.

Wide-open at Moderate Distance
Focus was on the doll's painted lower eyelashes

Moderate Distance at f/5.6
Focus was on the doll's painted lower eyelashes

Close Focus Wide-open
Focus was on the front star at the corner of the pewter box.

Close Focus at f/5.6
Focus was on the front star at the corner of the pewter box.

Close Focus Comparisons at f/8 (optimum sharpness)
Focus was on the flange edge of the watch bezel at lower left

Focus was on the flange edge of the watch bezel at lower left

Focus was on the flange edge of the watch bezel at lower left

Focus was on the flange edge of the watch bezel (not visible in this crop)

My initial post did not include any outdoor photos in natural light. This morning the weather was cooperative and I spent a few hours at Cathedral Park in Portland adjacent to the very graceful and often photographed St. John's Bridge. To be fair and to show both lenses off at their best, all photos were shot in RAW and taken with a hood. All photos were hand held using SR (ground was too sodden for a tripod) with the K10D at ISO 100. I figure that it is best to show the worst first. The two images below were taken of the bottom of the bridge deck and the deeply shaded concrete supports. The sky beyond had high cirrus clouds and the sun is just outside the frame to the left. Exposure is center-weighted using the green button recommendation with no adjustment.

Lens Torture!

Default Lightroom RAW conversion

There you see it folks. Veiling flare on the Tamron! The Vivitar apparently has greater flare resistance. That and its higher contrast allows it to handle this mess fairly gracefully. Since this is digital photography, there is always a second chance at greatness. Below are the same two images after a little massaging of the curves. The Tamron required a little more attention (significant contrast bump), but the results from both are now fairly pleasing. That is if you are easily pleased by the underside of bridges!

Lens Torture After a Little PP

Turning my back to the sun, I shot a few of a large concrete structure at the base of the bridge. Under less challenging conditions, the two lenses delivered comparable results with the Vivitar showing a slight edge in contrast.

The Sun At Our Back

Default Lightroom RAW conversion with a small exposure adjustment to the Vivitar shot.

In addition to the outdoor shots, I also shot a blank wall indoors under controlled lighting as the basis for histograms showing the transmittance and contrast differences between the two lenses.

Blank Wall Histograms

End Edit

This exercise was a real eye-opener. For the most part, in actual usage, it is awfully hard to tell the difference between these two lenses. The only real thing that I noticed is that the Vivitar required about a stop more light, regardless of aperture, than the Tamron. Whether this is due to coatings or optical design is anybody's guess. Edit:After spending some more time with the lenses, I think the difference in light transmission is closer to 1/2-1 stop.End Edit In summary:
  • Both lenses are sharp with good contrast
  • Both lenses have little or no CA
  • Distortion is not an issue for either lens on APS-C
  • Both lenses have pleasing color rendition
  • The Vivitar requires 1 stop of exposure compensation on average
  • Colors were somewhat cooler with the Vivitar
Yet to be done is some real-world outdoor shooting. The weather here has been crappy; but when it clears up, I will post additional comparison shots that will test how these lenses handle outdoor lighting and more varied subjects.

What does this mean? Maybe the Tamron will emerge as another cult-classic along with the Viv As for my personal decision as to which lens to keep...that is a hard one. I will have to see the results from the outdoor shots as well as do some comparisons on film where the winner will be my workhorse landscape lens.


After today's outdoor shots, I have to add a few more bullet points:
  • The Vivitar has better flare resistance than the Tamron
  • The Vivitar's contrast edge is readily apparent in outdoor shooting
  • Both lenses benefit from a hood
My conclusion remains much the same except that I have to admit that the Vivitar tended to be more rewarding on the subjects I was working with today. I also took a couple dozen B&W film shots. Those will likely determine which lens gets voted out of the bag.

End Edit

Post Script
I should probably not include these next two images, but feel that they are important to help maintain perspective in the continuing discussion of lens performance. Below are shots taken in the f/8 (optimum) test setup using the Pentax-DA 18-55/3.5-5.6 AL kit zoom set at 28mm. Dang, if the results aren't pretty decent...except for some mild CA...


(Still not sure if I should have thrown in those last two images...)

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