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10-16-2010, 01:15 PM - 1 Like   #1
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Rambling mid-range zoom comments

Some purely subjective comments about a few mid-range zooms. As usual, my original intent and incentive for comparing these lenses was to find some definitive reason to thin the herd. And as always, grading based purely on IQ comparisons didn’t offer any solutions. If for no other reason than to justify the time spent, I’ll offer a few Saturday afternoon observations anyway. This was in no waya test of anything.

Conditions were clear mid-day sunlight using a detailed building fašade with trees at about 100 ft distance. Shot off a bean bag rest using AF (or the AF indicator with MF lenses). Exposures spanned maximum F-stop to F16 at ISO 200 with neutral best JPG setting using K200D's. Comparisons were made with Faststone Viewer’s Compare mode with no PP’ing whatsoever. I’m not going to offer image samples here because there were just too many of ‘em and they weren’t organized for web viewing. They never seem to withstand squishing and re-sizing for the net anyway.

The lenses involved were:

Tam SP AF 28-75/F2.8 XR Di
Tam AF 28-80/F3.5-5.6 ASP
Tam AD-2 28-70/F3.5-22 CF Macro (44A)
Tam AD-2 28-70/F3.5-22 Macro (59A)
Sig 24-70/F3.5-5.6 ASP AF
Sig 35-80/F4-5.6 DL
SMC-A 35-70/F4.0 (PKA)
Tokina 28-70/F2.8-4.3 (PKA)
Tokina RMC 28-85/F4.0 (PK)

General observations (relative only to these specific lenses on this particular day) :

The average review results as posted in the PF Lens Review section are generally very reliable indicators of nominal lens performance. (I think that speaks well of the objective opinions expressed by folks in this forum as well as the reliability of the reviews themselves.)

As a general statement, with the obvious exception of those lenses with acknowledged weak reputations or low-end, economy-class kit lenses, there just aren’t any real dogs out there. Nevertheless, there are “different horses for different courses” – and jockeys. That’s “different tires for different tracks” for the motor racing crowd.

Among the better class of lenses, from F5.6 (or one stop above max zoomed aperture) up you really have to search to find deal-breaking IQ differences that aren’t attributed to inherent WA distortion in the mid-range zooms.

Color fringing, from all sources, is very well controlled in this class of lenses and rarely shows up unless pushed to the limit in contrasty situations. (This isn’t necessarily true in the longer telephoto FL ranges, IME.) What CF is there is easily corrected in PP with today’s software. Since I wasn’t shooting directly toward the sun or bright, point sources of light, flare simply wasn’t evident with any of the lenses.

Color cast, background blur (bokeh) and a purely subjective feel for rendition in a lens seems to be the most obvious differentiation in IQ among similar lenses in this class.

Location and size of the focus and aperture rings, direction of rotation, rotation arc vs. focus range and the torque-feel in zoom and focus functions are the most apparent mechanical issues aside from weight and size. Many of the smaller MF zoom lenses are simply a pleasure use from an ergonomic standpoint.

Higher usable ISO translates into very practical advantages for older, MF lenses by allowing for increased DOF and/or exposure limits not previously practicable with film.

In practical use, minor differences and unintentional errors in focus point, poor DOF bracketing, inappropriate choice of focal length, and lens-motion-blur due to low shutter speeds is far more noticeable to me than any inherent differences in IQ owing to lens design in this FL range.

Folks on a budget have a virtual plethora of quality, mid-range glass to choose from today in the used price range from nil-to $100 – especially if they’re willing to forgo the inconvenience and indignity of suffering from “auto-focus failure complaint syndrome”. And it provides an economical means to explore the applications for a new FL range while saving for the big-iron.

Using three different K200D’s, I couldn’t fault any of the lenses for focusing errors that couldn’t be directly attributed to the “nut that adjusts the focus point”. An O-ME53 magnifier with a split screen prism does wonders for focus accuracy.

I’ve never failed to be pleased by the quality and utility of the Tamron Adaptall-2 and SP class of zoom lenses. It would be interesting to see what would have evolved for Adaptall-type, APS-C and Di format lenses if OEM-specific, electric auto-focus designs hadn’t made it economically impractical to continue that concept. Maybe there'd be some real competition in the SDM world?

Two specific comments on lenses:

Images from the SMC-A 35-70/F4.0 (PKA) and the Tokina 28-70/F2.8-4.3 (PKA) manual focus zooms were nearly indistinguishable from the respected Tam SP AF 28-75/F2.8 XR Di at common apertures without side-by-side comparison.

And a used Sigma 24-70/F3.5-5.6 ASP AF might make a excellent, economical alternative for the more expensive Tamron or Sigma offerings for those on a tight budget.

H2

Oh, two lenses eventually got 'pink slips' -- more because of redundancy than performance. Bless 'em all.

10-16-2010, 10:01 PM   #2
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Nice post! Thanks!
10-17-2010, 08:25 PM   #3
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I wonder how the F 35-70 would hold up? It has bested multiple other lenses I've had in this range, but none of the ones you mention. I also really like the Rikenon XR 35-70, which is a constant f/3.5 and has its macro mode at 35mm.
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