Pentax K-5 - Three lenses, Low ISO performance.

Pentax K-5 15mm F4, 35mm f2.4 and 70mm f2.4 lenses


A second day of bright sunshine and a further chance to work with the Pentax K-5. This time alongside the River Severn at Bewdley. I took the 15mm and 70mm lenses as yesterday, and also took along the 35mm f2.4.


In the Dpreview review of the K-5 there's a line in the conclusion amongst the plus points. "Exceptionally low shadow noise in RAW files at low ISOs" Reviews and discussions of cameras these days seem to concentrate on what a camera will do at high ISO's and how much noise there is at ISO 3200 etc. Often the performance at ISO 100 etc. is either ignored or assumed to be OK. However, for those of us who rarely use anything over ISO 200, it can be quite important. The importance of Dpreviews comment can be seen below.


Pentax K-5 15mm F4 lens


The top image is the out of camera jpg. The shadow correction option is turned on, but the  foreground with the motorbikes is still too dark. The bottom image is after some work in Photoshop, and I have lightened the foreground substantially to show the bikes. This would normally generate a fair deal of noise, but in this case that hasn't happened. The bottom half of the image is very "clean" and shows no colour noise and only a very slight increase in luminance noise.


Here's another example.


Pentax K-5 15mm F4 lens


I've never seen such "elasticity" in a camera before. The K-5 has an excellent dynamic range but its ability to produce files where shadows can be lifted to this extent without generating noise is incredibly useful. The fact that it can do this while still creating a very "punchy" image with terrific colour is a real bonus. Here's a couple of further examples of what it can do with little post shooting work on my part. These are taken in very bright sunlight.


Pentax K-5 15mm F4 lens


Pentax K-5 15mm F4 lens


This is getting very close to reproducing what we see with our eyes. 


Here's a sample of what happens when I lift the shadows in an image using a camera that has high shadow noise at low ISO's. This is from a Canon 5D Mk II at ISO 100.






This has always been a problem with this Canon sensor. So "full-frame" doesn't always have the low-noise advantage. 


For the K-5 to produce results like this is very impressive. One thing it lets me do is to expose for the highlights, knowing that I've got a good chance of recovering detail in the shadows, without generating extra noise.


Pentax K-5 15mm F4 lens


In fact the files that I am creating from my K-5 are probably the best I've seen. I tried a few in Rawker,  the dcraw based raw conversion software I use to see what raw files are like without the software "fixes" that manufacturers add to their software. They came out very well indeed. Very clean, with no noise and very little CA and fringing. Excellent sharpness also. 


It seems that Pentax may have done very little to tweak the the sensor output. In an interview with Chris Pound from Pentax at Dpreview he said the following:- "When asked about how much input Pentax had into the design of the (Sony-built) sensor in the K-5, Pound explained: 'we had less input than we did in the previous generation, where we worked with Samsung.' He went on: 'Sony controlled the development [of the new sensor] but they have a very good history of that kind of design and it has proven very successful in the K-5."


Pentax K-5 70mm f2.4 lens


Using the K-5 in these real-world shooting situations has led me being even more impressed with the camera, than I was before. It seems almost designed for me personally. Small, light, great colour, terrific low-ISO performance with good dynamic range, fast accurate AF, high quality lightweight lenses, producing sharp images. Everything I want really. I was beginning to think that I would never get this in a DSLR, and its been a pleasant surprise that I can.


Pentax K-5 35mm f2.4 lens


On the lenses, the 35mm f2.4 is also a great little lens. For a Pentax prime its actually very cheap. The savings have obviously come in the construction, as its plastic through and through. However its excellent optically.


Pentax K-5 15mm F4 lens


So a very successful couple of days. Firstly that I managed to get out and shoot some pictures and secondly that the Pentax K-5 lived up to, and in many ways exceeded, my expectations of it. I enjoyed using it, and looking at the results. The first of many such experiences I hope. 


Words - David
Images - David and Ann