Thursday, May 10, 2012

Do It All at f/2.8: the Tamron 28-105 2.8



The fast standard zoom with a 35mm equivalent of around 24-70mm is generally considered one of the most versatile lenses.  There are photographers who say that they can shoot a whole wedding with that one lens.  You may want to know that there's one lens that can cover an even wider range of shots: the Tamron 28-105 f/2.8, the only lens of its kind to cover the entire range of 28mm to 105mm at a constant 2.8 aperture.

The SP AF Tamron 28-105 f/2.8 LD Aspherical IF is a full frame lens available in Canon, Nikon, and adaptall mounts.  Note: the adaptall mount has limited functions (for example, it is only manual focus).  The Tamron 28-105 has been discontinued for a while now.  It originally sold for around $849 in 1997.  These days it's available used anywhere from around $250 to $650.

This lens replaced the Tamron 35-105 2.8.  There were two versions of the Tamron 28-105.  The earlier version had "Tamron" written around the zoom ring. The latter version has a zoom ring with ribs instead of Tamron written on it.  The lens I have is the latter version.

Specifications at a glance:
  • filter size: 82mm
  • 15 elements in 13 groups (Source: http://www.fredmiranda.com/reviews/showproduct.php?product=242)
  • minimum length (without the hood): ~5 inches
  • maximum length (without the hood): ~7 inches
  • weight: 880 grams
  • minimum focal distance: varies from 0.44 meters (1.44 ft.) to 0.50 meters (1.64 ft.) depending on the focal length
  • minimum aperture: f/22
  • number of aperture blades: 9.  At f/2.8, the aperture looks perfectly round.

This lens is larger than the usual standard zoom, which is expected given that it is a full frame lens that covers such a wide zoom range and has a wide aperture.  Its body is wider than even the Nikkor 28-70 2.8D I used to have.  It uses an 82mm filter size.  When extended to its maximum focal length, it is about 7 inches long without the hood, longer than even a Sigma 50-150 2.8 (which is around 5.5 inches) and just an inch shorter than a Nikon 70-200 VR II.  I don't like to put it next to my Tokina 10-17 because it gives the latter nightmares.

The 28-105 when extended.  An easy target for male enhancement jokes.
The lens body is plastic but appears reasonably well constructed.  I don't find any parts that are wiggly or anything but smooth.  Even though it's plastic, it's heavier than your average lens, only slightly lighter than the all-metal Nikkor 24-70 2.8G.  However, I wouldn't say it's too heavy given its zoom range and aperture.

Features:
-  The Tamron 28-105 has an anti-slip torque mechanism to prevent lens creep.  Without the anti-slip in use, the lens will extend under its own weight while I'm walking around (though not from simply being on a tripod).  To engage the anti-slip mode, you simply pull the zoom ring toward the camera body (see the shot above with the lens extended - the anti-slip mode label is shown just above the zoom ring).  Once the anti-slip mode is engaged, the zoom becomes harder to rotate, thus preventing zoom creep.
- Internal focus.  Stationary filter ring regardless of focusing action.
- Low dispersion glass to reduce chromatic aberration.
- Aperture ring.  This is useful for changing the aperture on the fly when taking videos, or when using the lens with an older [film] camera.

aperture ring
Since there isn't a lot of technical information about this lens, I've decided to review it in a little more detail by comparing it to the king of the hill for Nikon, the 24-70 2.8G.  I'm not implying that the Tamron 28-105 2.8 is a substitute for the 24-70.  They have too many differences such as price and zoom range, but the 24-70 sample is intended as the "control" insofar as it's the best lens I have at the most similar zoom range.

I did three comparisons:
- the complete frame to show vignetting, distortion, and image quality at normal viewing sizes;
- 100% crop from the center
- 100% crop from closer to the border (though not literally the extreme corner)
I used manual flash on a light stand and shot at sync speed. I refocused the camera each time I adjusted the focal length.  In the case of the Tamron at 35mm and 50mm, I used manual focusing with live view for perfect focusing (my first set at those focal lengths were not correctly focused).  The Nikkor 24-70 hasn't had micro-focus adjustment yet.

TEST 1:
Here is a slideshow comparing the Tamron 28-105 to the Nikon.  If you prefer, you can click on the link to the web album instead.  First, you'll see the Tamron shot, then the Nikon shot.  You'll see a comparison at f/2.8, then 4.0 then 5.6, at the following focal lengths: 105mm, 85mm, 70mm, 50mm, 35mm, 28mm and 24mm.  For 105mm and 85mm, only the Tamron is shown.  For 24mm, only the Nikon is shown.


TEST 2:
Test 2 is the same as test 1 except that I'm comparing 100% crops from the center of the frame.  Web album here.



TEST 3:
Test 2 is the same as test 1 except that I'm comparing 100% crops from outside the center of the frame.  Web album here.



Observations:

  • 105mm and 85mm: The Tamron has decent sharpness even wide open.  There is significant vignetting that is mitigated as the lens is stopped down.  There is slight pincushion distortion.
  • 70mm: The Tamron is less sharp wide open than at 105mm or 85mm.  It improves as it's stopped down.  At f/4.0 it is slightly less sharp than the Nikon at f/2.8.  The Tamron has less vignetting than the Nikon at 2.8.  At f/4.0, the vignetting is about the same although the Tamron is a bit better.  At f/5.6, the Nikon has less vignetting than the Tamron.  The Tamron has slight pincushion distortion.
  • 50mm: Wide open, the Tamron is not sharp anymore, although sharpness improves significantly at f/4.0.  The Tamron has less vignetting than the Nikon at the apertures tested, particularly at f/2.8 and f/4.0.  The Tamron has very slight pincushion distortion.
  • 35mm: Wide open, the Tamron is noticeably soft.  Sharpness improves significantly again at f/4.0.  The Tamron has less vignetting than the Nikon at the apertures tested, particularly at f/2.8 and f/4.0.  The Tamron has no noticeable distortion at 35mm.
  • 28mm: Wide open, the Tamron is soft, although a bit sharper than at 35mm.  At 2.8 and 4.0 the Tamron appears to be sharper than the Nikon (focusing error?).  At 5.6, the Tamron is about the same sharpness as the Nikon.  In terms of vignetting, the Tamron and Nikon are more similar than at other focal lengths.  The Tamron vignetting is more pronounced than the Nikon at the edges, though the Nikon has vignetting that covers a larger percentage of the frame.  At 28mm, the Tamron has some moustache distortion.


CHROMATIC ABERRATION
The Tamron doesn't have a lot of chromatic aberration.  It's generally low enough that it can usually be automatically removed in Lightroom 4.

On the other hand, when shooting wide open at around 50mm, there is sometimes a soft glowing appearance around some bright highlights in the transitional area between being in focus and not in focus.  Here's an example:
Radioactive shirt?  No, it's just the Tamron's glow (45mm, f/2.8)
Note that there is a glow around the sunlit part of my son's orange shirt, and around the sunlit part of his hair.  But the part of the shirt and hair that are in shade don't have the glow.  There is also no glow on the sunlight on my daugther's arm or knuckles because they are closer to being in focus.

The glow is not the usual kind of spherical aberration because it only affects highlights and can appear anywhere in the frame (it's just as apparent at the center as at the edges).  It's not coma because it's omnidirectional (as opposed to the glow pointing in a particular direction).  Rather, it appears this effect is called "halation."

Here's another sample:
Note the glow around my son's right arm and shoulder.
By contrast, compare this shot, which has no glow under similar lighting conditions (in this case, because it's at 35mm).
34mm f/2.8

BOKEH
Reasonably smooth except in the transition area, which has some outlining.

Front and rear bokeh (105mm 2.8 SOOC)


FLARE RESISTANCE
OK except when there is a bright light source within or near the frame, in which case there is ghosting and a significant reduction in contrast.

FOCUSING
The version I have is for Nikon and does not have a built-in autofocus motor therefore focusing speed relies to some extent on the camera body on which it's mounted.  On my D3 it focused about as fast as the silent-wave motor-equipped Nikkor 28-70, i.e., autofocus was fast.  Focusing was fast enough that I was able to get usable (but not perfect) focus on continuous AF with our tot running toward me.  However, with low contrast subjects in dim light, it had a harder time focusing and hunted a bit.

Continuous AF (105mm 2.8 SOOC)

REAL WORLD SHOTS
Now that we've seen test shots, how does the lens perform in the real world?  Here are examples at various focal lengths (you can click on the photos to bring up the downloadable 1600pix versions).  Let's start at 28mm.

28mm 2.8
The focus point here was wrong - it was on the girl with the long black hair, but there is a good amount of detail even at this soft spot of the Tamron.

At 35mm:
35mm 2.8 SOOC
We saw from the tests that the Tamron was soft at 50mm f/2.8.  In the real world, here's what it looks like:
50mm 2.8 SOOC
And here's a 100% crop.  The texture on his shirt and some of the facial hairs are visible.  Not bad considering this is as soft as it gets.
100% crop

And another sample at around 50mm (this one is at 48mm) with sharpening applied.
48mm 2.8

Stopped down to f/4.0, the sharpness is not bad at all.
45mm 4.0

And stopped down further to f/5.6 it is fairly sharp.

50mm 5.6
Moving on to 70mm:

70mm 2.8 SOOC
And at around 85mm:
82mm 2.8 SOOC
In case you're wondering how the lens looks at 85mm stopped down to f/4:
85mm f/4.0 ISO 6400 - default sharpening, luminance noise reduction at 15
Finally, at 105mm:
105mm 2.8
OTHER PHOTOS
I like the portraits using this lens taken by Flickr member halpics2 (note: most of these were with cameras with an APS-C sensor therefore the focal length equivalent would be 42mm to 158mm)
http://www.flickr.com/photos/77345520@N00/304631343/in/set-72157594399136671
http://www.flickr.com/photos/77345520@N00/346118640/in/set-72157594399136671/
http://www.flickr.com/photos/77345520@N00/336697469/in/set-72157594399136671/
Check out his other shots with this lens here.

SUMMARY
+ Sharp even wide open at longer focal lengths
+ Decent sharpness at f/4.0 at shorter focal lengths
+ Versatile zoom range
+ Constant 2.8 aperture
+ full frame
+ inexpensive / good value at current used prices
- Soft wide open at 50mm and shorter focal lengths
- Halation at around 50mm at f/2.8.
- big and heavy
- because few people know about it, it may be harder to resell

Performance at f/2.8 is good at long focal lengths, not so good wide open at shorter focal lengths.  However, at f/4.0 it improves significantly so that it performs well at all focal lengths.  If you want good sharpness throughout focal lengths then you can consider this an f/4 lens with a bonus f/2.8 at longer focal lengths. :)

In practical terms, it's good for portraits with the ability to cover wide angles.  It's also good as a walkaround lens or when you otherwise want to bring only one lens to cover a diverse range of subjects.  Considering the current market value of a used copy of this lens these days, it's a reasonable alternative to a 24-105 f/4 lens (albeit without stabilization) or the Tamron 28-75.  It is a good alternative if you find the 24-70 a little too short for portraits (do you often find yourself racking out your zoom?).  Finally, it is also a good alternative if you use both a FF body and an APS-C body, and you want to use the APS-C body for telephoto.  When this is on an FF body, it perfectly complements a 70-200 on an APS-C body allowing you to cover 28 to 300mm at 2.8 without any gaps.

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