<Edited>
I just finished a comparison of four TC’s on the classic Tammy SP 180/2.5. The following comments are purely subjective and by no means was this a ‘test’. The purpose of the effort was to see if any teleconverters were going to provide a useful option and, if so, to identify the best of those I had available.
(There ain’t gonna be IQ pictures ‘cause I don’t believe they’re particularly useful for this purpose, especially after after being ‘squished’ through web browser filters. Or, it could just be I’m too lazy to upload dozens of pix -- your choice. If someone needs a particular image I can provide / PM.)
The Adaptall SP 180/2.5 lives up to its reputation as an outstanding lens . If you can live without auto focus and prefer to spend about a third of the new cost of an equivalent lens, get this one. You’ll find all the usual technical data on the Adaptall-2 web site.
This lens was very consistent in sharpness, contrast, and color across the full range of apertures as expected of lenses of this class. Contrast and color rendition were slightly “flatter” than some other high end glass with the latest Di coatings and baffles but well within
my “normal” expectations and ability to tweak with post processing.
Conditions were about F/8+ on a “Sunny Sixteen” cloudy day using a tripod and 2-second delay. Results were reviewed/compared in Faststone Image Viewer. All apertures were
as read via the camera using AV mode.
K200D with the SP 180/2.5 with default, best quality JPG settings, AV mode and ISO 200
Tamron Adaptall-2 teleconverters – SP 1.4X (#140F) and 2X (#01F)
Tamron-F 1.4X Pz-AF MC4
Tokina EL 2X PK/A
Equivalent APS-C focal lengths:
180 = ~250mm
1.4X = ~350mm
2X = ~500mm
At F2.8 (ie, minimum aperture plus one click): All four TC’s offered about the same degree of sharpness. The two AD-2 elements seemed to provide slightly ‘cleaner’ bokeh and contrast. (F2.5 was definitely usable. The K200D displayed F2.4 (!) via the PK/A adapter.)
At F4: Again the dedicated TC’s were slightly better in both sharpness and contrast although post processing was able to bring all images to about the same level. Without a beak-to-beak comparison I'm don’t believe I’d be able to reliably differentiate between the two TC pairs after PP.
At F8: At this point, the dedicated AD-2 TC’s begin to stand out, especially in the out-of-focus areas. Better contrast and sharpness were apparent in “random” screen selections and I was confident I could differentiate between the TC’s.
At F16: A noticeable degradation in IQ was beginning to appear with or without the TC’s. Not bad, but noticeable and contrast was definitely beginning to suffer. The choice of TC’s wasn’t a controlling factor compared to the effect of the smaller aperture in my opinion.
General conclusions: If you’re serious about using TC’s to extend the range of this lens, the dedicated AD-2 elements seem to be well worth the cost from about F4 – F11. Above or below that range I didn’t see a significant difference in overall quality – especially in typical field use where precise focus and handheld camera shake may be deciding factors. Both Tamron 1.4X TC’s provided results
at least as good as the usual consumer 70-300 zooms at their best and were more consistent across a wider range of useful apertures. Under the conditions noted, PF simply wasn't apparent other than minor traces above F16 with the Tokina 2x TC.
If I had to choose just one of these four TC’s, I’d be very tempted to pick the Tamron 1.4X Pz-AF for its additional utility with other AF lenses and its satisfactory results with both the SP 180/2.5 and its SP 300/2.8 partner. Fortunately, either of those lenses often seems to come with one or both of the AD-2 TC’s when bought used today.
H2
With a prompt from a member very familiar with tele lenses on the DPR forum, I just confirmed that the 2X SP200 TC DOES fit OK on my SP 180/2.5 lens.
Last edited by pacerr; 01-10-2010 at 08:38 PM.
Reason: New info
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