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Friday, October 06, 2006

Ctein: Pentax 67 300mm* ƒ/4 ED(IF) Lens Review

*450mm-equivalent on the Pentax K10D and other K-mount DSLRs.

by Ctein

click for full-size illustration
This spectacular photograph of fresh, red-hot pahoehoe lava shows off the 300mm ED(IF) lens at its best. Ctein was less than four meters from this flow, much closer than the older 300mm lens could focus.

The original Pentax 67 300mm ƒ/4 lens is a 35-year-old design. It combined high speed and compactness with good optical performance for 1970, but its contrast is low by today's standards. It has a lot of secondary chromatic aberration, and doesn't focus very closely.

Today's Pentax 67 300mm ƒ/4 ED(IF) fixes both problems. It incorporates extra-low dispersion (ED) elements that eliminate all traces of color fringing . Internal focusing (IF) goes down to a remarkable 2 meters, over 1/6X magnification. Even at the closest distance the image quality is superb; I could just barely see the very slightest amount of smearing, but no color fringing, at the edges of 11x14" prints.

click for full-size illustration
The old (left) Pentax 300mm ƒ/4 lens and new (right) 300mm ED(IF) ƒ/4 lens. Note the narrow depth of field scale on the new lens.

The focusing ring turns smoothly with very little effort. That's a good thing, because focusing is much more finicky, and I found it very difficult to accurately focus the new lens. The focusing ring on the old 300 mm lens has +/– 2.5mm of travel within the depth of focus at ƒ/4. The new ED(IF) lens has only 0.6 mm of travel. Partly this is an inevitable consequence of the much longer focusing range; partly it's because the total travel of the focusing ring on the new lens is only 225 degrees, as opposed to 270 degrees on the old lens.

That's my only serious complaint about this lens. Its image quality is vastly superior to the old design. Even with difficulty focusing, my photographs were crisper and sharper over the entire field than I'd ever gotten before.

click for full-size illustration
These are enlargements of 3mm-wide regions at the edges of negatives made with the old 300mm (left) and the new 300mm ED(IF) (right) lenses. Note the pronounced red-green color fringing produced by the old lens.

Close focusing was indispensable on my last trip to Hawaii. I was able to photograph molten lava from safe distances but close enough to fill frames with exactly the compositions I wanted. There is no way I could have photographed the lead ilustration above with my older 300mm lens. I was less than 4 meters from the lava (and, yes, it was very hot, thank you for asking), much closer than I could've gotten with the old 300mm. Even if I'd used extension tubes with the old lens, chromatic aberration would've smeared out the myriad pinpoint highlights at the periphery into distracting little rainbows and obscured the fine detail.

The new 300mm lens is just a bit larger and heavier than the original. It still takes 77mm filters but unfortunately lacks the built-in lens hood of the original. It comes with a soft storage pouch instead of the old-fashioned hard case. The pouch compresses nicely when empty, definitely more convenient for carrying around. I have to trust it offers sufficient protection.

Another superior Pentax lens. I'm saving my pennies for this one, too (like the previously-reviewed macro lenses).

Posted by CTEIN


eolake said...

They made a brand new lens for a medium format film camera??

8:03 AM  
tsj said...

Outstanding lens, it even works well with the Pentax 2x; although you still wish you had a real 600mm.

8:14 AM  
MJ said...

I suppose if I am going to point out that it's a 450mm equivalent on a DSLR, I should point out that it's a 150mm equivalent on 6x7...



8:19 AM  
David A. Goldfarb said...

I just got back from B&H;, and upstairs in the used equipment department someone was looking to buy a Pentax 6x7, so they had all the ones they have in stock out on the counter, stacked like cordwood.

10:47 AM  
oren said...

stacked like cordwood

Yikes! As of a moment ago, the B&H; used equipment listing on the web showed nine of them in stock...

12:38 PM  
Morven said...

Every time you guys write about the Pentax 67 and its lenses, it makes me more tempted to acquire one. Even if "film is obsolete" and all that.

5:44 AM