SMC Pentax 02 5-15mm f/2.8-4.5 ED AL IF Q
The Q brings new meaning to the term Compact System Camera, how does this standard zoom perform?
The Pentax Q is the smallest sensor interchangeable lens system camera available, but it packs a pretty big punch. The BSI sensor used performs a lot better than its size would indicate, and the camera is made exceptionally well. It feels like a top of the line Pentax shoved into a point and shoot. Enough about the camera, I will review that some other time, this review is about the lens.
The issue with such a small sensor is it requires very high resolution lenses to focus the light, and do this at large apertures before diffraction starts to take its toll above f/4, so ideally you want apertures no smaller than f/4 as a max aperture, which this lens exceeds at the tele end of the range.
This lens has a 5.5x crop factor from full frame, but 4x from APS-C, so this is like an APS-C 20-60mm f/11-18 lens, which is actually a pretty decent range in which to use a kit lens, but think of it as a good light lens. It is great for walking around a sunny town or hike in the mountains, etc. What it is not good for is hand held low light. Since the physical aperture is around f/2.8-4.5 it focuses well in low light, but the camera has to use ISO 3200 a lot, and on such a small sensor ISO 3200 isn’t pretty.
Some people wonder why use such a small aperture equivalent lens? Why not just use a normal point and shoot with similar lens F range? Sometimes it is nice to be able to change lenses. There is that satisfying click as the lens locks into place, and it is nice to be able to change to a lens ideal for a situation. I don’t want to be stuck with only the standard zoom. Also, if you are familiar with a Pentax SLR, the Q will be straight forward to use. It is laid out almost the same, the only real difference is the buttons are smaller. Finally, with the Q’s new pricing it is actually significantly cheaper than a lot of the premium compacts with fixed lenses.
Lets get on with the review:
The lens is an 8 element in 7 group design, with a built in 4x ND filter (2 stop) and leaf shutter. The ND filter is wonderful because of the cameras relatively slow 1/2000 mechanical shutter speed, and SP coating to avoid smudges. The lens uses 5 diaphragm blades, but it is hard to get much out of focus unless you are at minimum focus and around 10 or 15mm. It is wonderfully constructed for such a tiny lens. It is mostly metal exterior and mount with plastic internals, but it is solidly built with little barrel wobble. It is a lot like a Sony NEX lens, but with nicer feeling metal (they use some slick finish, where this has a nice textured finish). It is a light weight at 96 g and uses a standard 40.5mm filter thread size.
Here I show the lens next to the relatively small Samsung NX 18-55mm to show just how small the lens is. It is much smaller than most pictures imply. Again, that Samsung lens is pretty small for a kit zoom.
Also note that the Pentax is reversed, the wide angle is the most elongated position. At 15mm it is only 1 or 2 mm longer than it is at 10mm as shown.
So, how does this little lightweight perform?
Comments on the Results
Again, this is a tiny sensor and the scales on the graphs are set for a 12 MP sensor. What we are seeing is the lens is having trouble resolving as well as a larger 12 MP sensor in a camera like an E-P1. This is expected since the pixels on the small Q sensor require a much higher resolution lens to make the most use of them. Basically the Q system will be limited by the lenses. Larger sensor cameras are largely limited in resolution by the sensors, and not the lenses, until more recently when they started going above 10 MP. This is when you saw all the new lenses from Nikon and Canon to take advantage of the extra sensor resolution.
As it stands, the Q has a Nyquist frequency of 3000 LW/PH (number of pixels on the vertical edge), which is 1500 LP/PH or 357 LP/mm (4.2 mm high sensor). For my 20 MP Samsung the Nyquist frequency is 3648 LW/PH, or 1824 LP/PH = 117 LP/mm (15.6 mm high sensor), so the Q requires lenses with 3x the resolution to max out the sensor.
So that being said, the MTF looks lens limited across the frame. I will have to test more lenses to see what a “good” value is, but right now you are looking at about 6 effective MP from the camera. This is still very good. I have some 5 MP C Mount lenses coming and will see how those compare (although they are 5 MP at 2/3″ sized sensor, manufacturers really don’t say what they mean by 5 MP).
I think this standard zoom is very good at 5mm, good at 8mm, and fair at 15mm.
Distortion is fine if corrected, but if uncorrected it is severe barrel distortion at 5mm and very light barrel distortion by 15mm, steadily gets less as you zoom.
Lateral CA is well controlled and a non issue. I don’t test longitudinal CA with this relatively deep depth of field kit lens. I didn’t notice much though, even close up at 15mm.
Flare resistance is average for a standard zoom. You will see aperture ghosts if the sun is in the frame.
I measured the corrected focal length to be 5.2mm based on 1:197 magnification at the wide end and 15mm at the 15mm setting. Uncorrected was 5mm to 15mm. This isn’t a highly accurate way to measure focal length, but it is easy enough to do when I have it setup to photograph the chart.
Pros and Cons
- Resolution across the frame at 5-10mm
- Marginal at 15mm
What you need to know with the Q is you are never going to maximize the resolution of the sensor. They push more MP in these small sensors for marketing, but they just don’t need it because of physical limitations in how optics work. You would have to have an aberration free lens at f/2.8 or 4 or something to max out the Q, which isn’t going to be cheap.
This isn’t a bad thing, just a limitation of a smaller sensor. Thankfully, the Q is still plenty good for fairly large prints. This is a good lens, and I do recommend it. If you shoot RAW apply liberal sharpening, the camera does this for you in JPEG. Sharpening will dramatically increase your image quality, especially at the wider settings where the MTF20 is fairly good.
Pentax 5-15mm f/2.8-4.5 Zoom Lens for Q Mount Cameras on BHPhoto in the US to support the site.
Pentax 5-15mm f/2.8-4.5 Zoom Lens for Q Mount Cameras on Adorama in the US to support the site.
Pentax 02 Standard Zoom Lens for Pentax Q on Amazon in the US to support the site.
The gallery images have some standard lightroom sharpening applied. I set it at 65, radius 1.2, detail 55, and masking of 43.