(1) At First Glance
The build quality of this lens is exceptional, everything feels very solid and well engineered. The entire body and even the lens cap are made
of aluminum (except for rubber/plastic rings, the knob and the dial). It's definitly on the heavier side at 1070g but understandable for its size.
(2) View Angle (82.70° horizontal / 66.85° vertical / 95.46° diagonal)
Corresponding to approximately 19.5mm on a 35mm full frame sensor, the view angle is good enough for most wide angle landscape shots.
Except for a handful of unusual occasions (i.g. Horseshoe Bend, AZ), I personally hardly go any wider than 16mm (on 35mm FF). Since this
lens will convert to a 15.5mm (on a 35mm FF) super-wide angle with a full-frame 645 sensor, I think this will remain as the wide end of my
work range.
(3) Optical Performance
The D-FA 645 25mm shows very impressive resolution across the frame, although it remains to be seen how it performs with a full-frame 645
sensor. With the current cropped sensor of 645d, even the extreme corners look very sharp and contain fine details. I would love to compare
this lens to Rodenstock Digaron-S 23mm, both of them seem to boast exceptional performances, but I am personally curious about how the
state-of-the-art 645 full-frame retro-focus superwide angle lens can stack up against high quality short-focus superwide angle lenses.
(4) Chromatic Abberations
This lens shows a substantial amount of CA, which can mostly be fixed by using any lens correction software. Although Pentax has not
announced the newest version of RAW converter or a correction profile for ACR, you can still use lens correction filters of Photoshop to partially
correct them.
100% crop from raw sample #4.
A brief test reveals that the longitudinal CA is not an issue even at f/4, (as can be seen from the image of the focus test chart, no color cast
in the out of focus areas). At f/10-13, which is the typical aperture range for landscape photography, longitudinal CA is almost non-existent
(due to smaller aperture) and most of the CA is lateral and therefore correctable.
Focus test chart can also show longitudinal chromatic abberation in natural light.
I have no idea why Pentax didn't use any low-dispersion elements for a $5000 lens. I've yet to carry out tests at wider apertures, but I don't
think it would matter that much to a landscape photographer like me since I hardley shoot any wider than f/8.
(5) Filter Compartment
Creating an internal filter compartment in the mid-section of the lens was a fantastic idea and it works perfectly. Using the plastic dial, a polarizer
can be easily rotated and this saves you the trouble of purchasing a large (and very expensive) polarizer and sacrificing one slot of your filter
holder. You can also separately purchase a 40.5mm ND8 filter from Hoya, which can be very useful for shutterspeed control.
(6) Using GND Filters - Custom Filter Holder
Since nobody has manufactured a dedicated filter holder for this lens, I had to fabricate one from a cheap abs pipe and Cokin z-pro filter holder.
At Home Depot, I picked up a small end cap hub that has a slightly smaller diameter than the front section of the lens, cut off the cap part,
converted it into a short cylinder and glued it to the back side of the Cokin Z-pro filter holder. I had to bore the cylinder a bit for a proper
tolerance and lined it with black velvet. FYI, after wasting a fortune on a number of different materials, I settled down on fake adhesive velvet
that I picked up from Daiso. After cutting and grinding, spray painting is a must and now you have a custom filter holder. You can use one 4X6
rectangular filter without vignetting.
(7) Custom Focus Mirror
I also fashioned a custom focus-mirror that can be attached to the lens. For precise DOF control, I find myself focus-stacking quite often,
and if your camera is on your eye level and you are shooting horizontal, there is no good way of quickly changing the focus. So I purchased
a small inspection mirror at a hardware store, took off the handle and screwed it to a reusable rubber twist tie. This can also be used with
different lenses for the same purpose.
Mirror :
Amazon.com: General Tools 557 2 1/4-Inch Diameter Inspection Mirror: Home Improvement
Tie :
Amazon.com: Nite Ize GT18-2PK-01 Gear Tie Reusable 18-Inch Rubber Twist Tie, 2-Pack, Black: Home Improvement
(8) A Sample Image and 100% Crop (Processed with ACR, Sharpening : 75/1/50/30)
Alamere Falls, Point Reyes National Seashore, Bolinas, California
100% Crop #1
100% Crop #2
100% Crop #3
100% Crop #4
(9) More Samples
It has been a slow season for landscape photography, so I haven't got a chance to utilize the full-potential of this lens. I will add new pics
as soon as they are available.
Ano Nuevo State Park, Pescadero, California
Memorial Church, Stanford University, Palo Alto, California
Near Pigeon Point Lighthouse, Pescadero, California
Gray Whale Cove, Montara, California
Schwabacher Landing, Grand Teton National Park, Wyoming
Sutro Baths, San Francisco, Caifornia
(10) Samples for Download (RAW)
http://www.harkleephotography.com/D-FA_645_25mm/Pentax_D-FA_645_25mm_Sample_01.PEF
http://www.harkleephotography.com/D-FA_645_25mm/Pentax_D-FA_645_25mm_Sample_02.PEF
http://www.harkleephotography.com/D-FA_645_25mm/Pentax_D-FA_645_25mm_Sample_03.PEF
http://www.harkleephotography.com/D-FA_645_25mm/Pentax_D-FA_645_25mm_Sample_04.PEF
(11) Latest Work (With Other Lenses)
Grotto Geyser, Yellowstone National Park, Wyoming
Lake Tahoe, California
Bay Bridge from Yurba Buena Island, San Francisco, California
Bonsai Rock, Lake Tahoe, Nevada
Garrapata State Beach, Carmel, California
Zephyr Cove, Lake Tahoe, Nevada
Lake Tahoe, California
Thanks for looking, you can comment or PM with any questions and I would be happy to answer them. Thanks.
- Hark
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