Tag Archives: 45mm

smc Pentax-FA 645 45mm f/2.8 review

After spending an hour with the 45mm on the Pentax 645D and capturing a variety of images, I headed back to the computer to evaluate the results. I’ve spent a over a week in denial. I’ve read online at the disappointing results of the manual focus version of this lens and somehow hoped the autofocus version wouldn’t be in the same boat. Not so.

Back to the brick wall…

Bear with me on these as there is a practical example at the end. For some users, the same soft detail in the corners issue that plagues the the 55mm may not be a characteristic that bothers them. When a client points out that the image is soft during a shoot, that is a huge problem in my books. 100% crops processed with sharpening but no lens corrections are below with f/stop noted underneath. The corner crops are shown from the lower left hand corner, however all four corners showed the same effect.

smc Pentax-FA 645 45mm f/2.8 lens on Pentax 645D – overall view

Center crop @ f/2.8 – soft, lacks in contrast

Center crop @ f/8 – improved sharpness and contrast

Center crop @ f/16 – sharpness is similar to f/8, little degradation from diffraction

Lower left hand corner @ f/2.8 – completely unusable (vignetting as expected)

Lower left hand corner @ f/8 – sharpness is improved, but doesn’t compare to the center

Lower left hand corner @ f/16 – still not delivering the detail of a 40MP sensor

Granted a photographer is not going to be making money shooting brick walls. As a more practical example, how does this affect image quality when shooting the front of a building? The excellent “Tapenade” restaurant in Steveston provides an example.

Positioned square to the building, this is the view of the south side.

Taking a center crop just to the left of the sidewalk and entrance shows good contrast and sharpness at f/9.

Sliding over to the left side of the image is another story. I’ve used Lightroom 3.3 to process the DNG files. Lens corrections were shut off to show a “truer” version of the results from this lens. I’m not averse to using technology wherever possible, so a version of the left side image will be shown with lens corrections turned on, too.

The grass and hedge are becoming a green blob without the detail shown in the center crop. There is also lateral (or transverse) chromatic aberration visible in the shutters. Turning on the lens correction feature in Lightroom 3.3 / Camera Raw 6.3 resolves this issue. Unfortunately it doesn’t improve the sharpenss.

While small JPEG crops don’t really cut it to show the issues being discussed here, the effects are certainly visible. Should you have sufficient bandwidth and want to see the original DNG files, they are available for download from the links below. Each files is nearly 70MB in size.

Brick Wall image with 45mm lens at f/8
Restaurant image with 45mm lens at f/9

The Pentax 645D is a very capable medium format digital camera. The larger sensor compared to the 35mm full-frame cameras and lack of an anti-aliasing filter gives the camera an edge when high quality glass is used. Lens choice is key with this camera and the 645D owner needs to closely evaluate not only what is sufficient for their requirements, but how their particular lens performs as manufacturing tolerances come into play. Also, with so many used 645 lenses on the market, you don’t always know the history of the second-hand lens you’re putting on your camera.

smc Pentax-FA 645 45mm f/2.8 arrival

I picked up my 45mm lens today for the Pentax 645D. Given the disappointing results with the new “digitally optimized” 55mm, I’m hoping this lens will fill the gap between my 35mm and 75mm lenses. If not, I’ll be continuing my quest for a decent “normal” focal length lens for this camera.

The rainy days have subsided once again, so I’m hoping to get a few photos shot tomorrow. As with the other lenses on the 645D, I’ll be particularly interested in corner sharpness as well as overall quality.