Photography News Issue 33

Photography News | Issue 33 | absolutephoto.com

Camera test 31

Performance: imagequality

No filter

AA Filter, type 1

AA Filter, type 2

Original image

Images These shots were taken with the 24-70mm f/2.8 using exposure settings of 1/400sec at f/11 and ISO 200. Images were processed through Lightroomwith default sharpening applied.

Using an anti-aliasing (or optical low-pass) filter helps avoid colour artefacts and interference issues like moiré on scenes with very, very fine detail that are difficult or even impossible to resolve post-capture, but it also impacts on ultimate image quality. This puts the camera makers in a dilemma and explains why we have cameras either with or without AA filters (Fujifilm X-T1, Nikon D810) and some with AA filters with a cancelling option (Canon EOS 5DS/R, Nikon D800E). Pentax has taken another route and the K-1 sensor is free of an anti- aliasing filter but has the option of simulating the effect at the time of capture. There are two strengths available and what happens is that the camera’s shake reduction

system actually vibrates the sensor at a microscopic level to blur the image and give an effect as if the sensor had an AA filter. It works best with shutter speeds at 1/1000sec or slower and there is an AA filter bracketing option to cover your options if you’re not sure if you need it or not. With the high resolution and very tiny pixels of modern cameras moiré pattern is not that common so going AA filter-free is certainly a sensible tactic. You’re also not going to see the effect anyway on a camera monitor so if in any doubt use the AA filter bracket – be warned though, it does gobble up memory. I shot a good number of AA filter brackets of finely detailed outdoor scenes and then spent ages poring

over images on screen at 100% and 200% to see, one, if there were any artefact problems on the K-1 with its anti-alias filter-free sensor and, two, if the AA filter cured any such problems. To be honest, this is needle in the haystack stuff and serious pixel- peeping territory. The good news is that I couldn’t find any moiré or colour artefact issues in the first place, but yes, the differences between no AA filter, type 1 and type 2 can be observed at high magnification. So the upshot is, you are going to have be very unlucky to experience any artefacting issues and should you think that you are likely to have problems, then the K-1 has the weaponry to resolve them.

Image The K-1 proved very consistent in the exposure department. This scene is inside Tower Bridge with a 24-70mm.

Performance: Pixel ShiftResolutionmode

Original image

Normal Raw

Pentax’s Pixel Shift Resolution mode is an option if optimum image quality is needed, provided the scene suits and you have a solid tripod. Take a shot in this mode and you see the monitor fills with four small thumbnails, one after the other, as each exposure is made. Then you get a ‘Data being processed’ message for a few seconds, followed by the writing to card LED flickering for another 10secs or so – during this time, the camera is locked. The mode works by capturing four images with the sensor moved by one pixel up, down, left and right between each one so that each individual pixel site collects red, green and blue light – the Bayer sensor pattern has twice as many green pixels as blue and red so this system records two lots of green data. With three times as much data, there’s the opportunity for less noise and superior colour reproduction. Of course, this has an impact on file sizes. JPEGs captured using Pixel Shift Resolution are similar in size to normal JPEGs, but Raw files are around 200-210MB compared with 50-60MB for a normal Raw. From the shooting aspect, you need the camera on a very stable tripod because if the camera moves by a tiny amount during the sequence of four exposures, which takes a couple of seconds, even at high shutter speeds, you have a problem. I tried using Pixel Shift

handheld without success. I also tried hand-holding the camera but supporting it on a fence post, cast iron bollard and on a tripod but again with no success. From the subject’s perspective, any movement is a problem. There is a Motion Correction feature available and this is definitely worth trying because it does work. I shot the same scene instandard Raw, with Motion Correction Off and On. The Motion Correction On DNGs I put through Lightroom and Photoshop did not work and the blurring of tree branches swaying in the breeze was clearly evident. The same files through SilkyPix, the software that came with the K-1, were much better and the same branches were sharp but the image was still not perfect and there was double imaging. I put the same Raws through Capture 1 v9 and the images were perfect with no double imaging, blur or artefacting at all. I did try Pixel Shift Resolution with high ISOs too, shooting with and without the mode. The Raws were processed through Capture 1 (there was a bug with Lightroom at the time) and the results compared with the standard Raws. Yes, there is a benefit in terms of noise of around 1EV, ie. the ISO 6400 with Pixel Shift shot was better saturated and the noise was the same level but more sharply defined when compared with the ISO 3200 shot without the mode.

SilkyPix Motion Correction 0n

Capture 1, v9, Motion Correction 0n

Images With a solid support and a suitable scene, the Pixel Shift Resolution does deliver better JPEGs and Raws with less noise and slightly superior colour reproduction so when the best quality is needed, the mode is worth using. If there is any movement in the scene, the Motion Correction On setting must be used. In this test, we found only Phase One’s Capture 1, v9 processed the file correctly. Even with the supplied SilkyPix software, there were obvious problems. These images were shot on a sunny day using the K-1 and a 24-70mm f/2.8 lens. There was a gentle breeze. The same DNG file was put through the three softwares.

LIghtroomMotion Correction 0n