SMC Pentax 01 8.5mm f/1.9 AL IF
This is one tiny standard, with a very nice aperture of f/1.9. How does this little beauty perform?
This 8.5 mm lens is a nice standard lens of about 35mm in APS-C or 50mm in 135 format terms. The front plane is so flat it looks like a filter element, but examining the lens patent (US20120268834A1) it looks like the front element is just nearly flat on the front surface.
The build quality is good, but light weight. The lens appears fairly fragile. The barrel is plastic, but feels high quality. The mount is metal. My only issue is feel, the focus ring is a bit small for me to get a good grip, and not to mention my hand tends to go in front of the lens when I am trying to manually focus.
The lens has a lot more girth than necessary, but in part it is filling out to the mount and leaves room for a focus motor. The filter threads are the standard 40.5 mm, with a fairly curved 5 bladed diaphragm. Focus is a reasonable 0.2 m (7.9 inches), but this won’t result in a lot of magnification at 8.5mm but it is about 4 inches closer than the kit zoom, which is fairly substantial. Looking at my keyboard this is about 5 keys across on the rear display at minimum focus. Weight is negligible at 37 g. Unfortunately, this lens is no longer available for purchase. Pentax needs to make this one available new.
How does this tiny prime compare?
Lets get on with the review:
Comments on the Results
Sharpness is very good to excellent across the frame, and central sharpness is excellent. This lens is excellent from wide open. Shoot from f/1.9 to f/4 without hesitation, and diffraction will be slightly noticeable by f/5.6 and beyond. With all these Q lenses you will notice the resolution is a little less than optimal, that is because the sensor has very small photo sites which require very expensive lenses to resolve.
Distortion is extreme 3.5% barrel distortion without correction. Corrected it is mostly negligible, but will come at the cost of decreased corner performance from what the charts show.
Lateral CA is slightly noticeable at large apertures. Longitudinal CA isn’t very noticeable due to the short focal length and deeper depth of field, but it is present and fairly strong.
Flare isn’t great, the frame will turn purple with too much sunlight. I figured the SMC coating would be better, but maybe the sensor is prone to flare off the cover or something (reflections between sensor cover and back of lens).
This lens also has a white balance shift from f/1.9 to f/2.8 or so just like the Pyxis 16mm f/1.4 I tested. This isn’t a huge deal if you shoot JPEG or use default WB, but could be a problem if you sync WB manually between RAW photographs, you should check them based on aperture (filter in Lightroom on the 8.5mm lens and f/1.9 aperture for example).
I measured the corrected focal length to be 8.3mm at 1:197 magnification.
Pros and Cons
- Resolution/Sharpness across the frame from f/1.9
- Overall Optical Performance
- Compact and Light
- Depth of field still fairly deep
- Native Distortion
The images have excellent contrast and are nice and sharp. Make sure to apply distortion correction if you shoot your own RAW, it will be applied automatically in camera for JPEG.