Google open-sources extreme JPEG compression

18 Mar

I previously criticised JPEGmini, a commercial program that promised to reduce JPEG size by focusing on the way humans perceive colour. My repeated finding in using the program was that it was unable to provide better compression than GIMP’s JPEG export – and GIMP is free!

Now Google has fielded Guetzli, a new JPEG compression engine that Google describes as drawing on psychovisual research. So in that aspect, it doesn’t sound much different from JPEGmini. It is, however, open-sourced, and according to Google, promises 35% smaller files compared to the open source JPEG library libjpeg, which without much doubt must be the engine used by GIMP.


Original on the left, libjpeg, center, and Guetzli on the right. Google notes the paucity of blocky artefacts in the Guetzli output, but I would also note the loss in vibrance, a typical approach in noise reduction.

Guetzli, like other recent advances in imaging, is slow. So slow, in fact, that it sounds like its use case is currently limited to very frequently downloaded items like website banners, where spending a lot of time optimizing will considerably reduce traffic.

Alternatively, though, Google could put its weight behind FLIF, supporting it in Chrome/Chromium and thereby putting pressure on other browsers to also support it. FLIF promises to provide current-best lossless compression and is interlaceable – and open source.

Guetzli might give a smaller file than FLIF, but only with more lossy compression, and it sounds like it’s currently a lot slower (I have seen no figures comparing the two).

From photographers’ perspectives, Guetzli may have one further use case. Images with such highly optimised compression are unlikely to be very usable for further editing, so for showing off your work on the web while spoiling the fun for potential thieves, Guetzli or any higher-compression tool might be a good choice (but remember – Google can “guesstimate” the image back with RAISR).

Pentax KP vs. Nikon D500: white balance

16 Mar

Continuing my series on the Pentax KP, and possibly starting a sub-series comparing the Nikon D500 against it, today my attention was drawn to ephotozine’s Pentax KP sample photos, particularly the colour section:


Pentax KP (top) vs. Nikon D500 – ISO 200 (left) to ISO 819,200.

Particularly the ISO 819,200 sample from Nikon seems to be soaked in yellow, although the ISO 409,600 sample also seems affected. Here’s the 819,200 comparison, with two attempts to fix the Nikon’s white balance in post:

Screen Shot 2017-03-16 at 00.21.40

Pentax KP (left) vs. Nikon D500 OOC, Nikon D500 with my own special WB procedure, and finally Nikon D500 after “color->auto->white balance” from Gimp

If “fluorescent” white balance is used in the Pentax, it gets even further ahead of the Nikon – an unfair comparison perhaps, but it’s only a single step of configuration and straight out of camera:

Screen Shot 2017-03-16 at 00.05.09.png

With even more prodding, I eventually got the Nikon image to behave. I managed to keep noise levels on par, but keep in mind that it’s a fair amount of work, and you really have to know what you’re doing in Photoshop or Gimp to get this kind of result – remember the one button fix is the image on the far right, and it improves things, but doesn’t really “fix” the problem. Cutting to the chase, here’s that final result:

Screen Shot 2017-03-16 at 00.48.24

Even using the Pentax’ default white balance, it does impressively well, keeping in mind we had to massage the Nikon image for several minutes to get it into decent shape:

Screen Shot 2017-03-16 at 00.52.50

The bottom line is that in terms of colour, the Pentax produces reasonable JPEG output even at very high ISO, while the Nikon D500 takes considerable time in post-processing to achieve a competitive result. The Nikon is not usable as a JPEG camera at this high ISO and I would instead recommend, if using the D500 at all, to shoot raw and use a raw converter, in which case it’s the raw converter’s job to give you a reasonable-looking image (this will be the next part in this series, if time allows).

Pentax’ PLM and DC lenses explained

2 Mar

DC (“direct current”) is a kind of focus motor that has been used in Pentax lenses for some time. While it is quiet, it’s not entirely silent. Pentax’ most recent 55-300mm lens features a new type of motor branded as PLM. Here is what Pentax representatives had to say about it in an interview:

The PLM design can quickly activate and allow for faster focusing, but the lens element must be low weight due to limited power (torque).

The DC motor can generate high power (torque) with deceleration mechanisms, which is better for lenses with larger focusing elements. A DC motor can be driven at high speed, but there is an issue that a little sound is generated.

Generally, we use the what we feel is the best focusing mechanism for each specific lens design.

It would be reasonable to suspect that the 55-300mm’s new optical formula and narrower aperture were needed to allow the faster, silent motor to be used, although it should be noted that, like the recent 18-50mm kit and non-kit zoom lenses, the new 55-300mm lens is collapsible to a somewhat smaller size, with the difference between collapsed and uncollapsed size being more pronounced in the 18-50mm.

In the interview, the representatives went on to explain that they do not expect to see PLM in a large aperture lens any time soon, instead putting their money on researching other kinds of motors as well as algorithms to improve autofocus.

Sony a99 II: No C-AF in manual video?

15 Feb

Here’s the relevant section of Kai Man Wong’s review of the a99 II, discussing its video capabilities, the f/3.5 caveat, and the missing option to have continuous autofocus when video exposure is set manually:


I take my hat off to Kai for delivering a more thorough review of this camera, and in a shorter space of time, than other frequented outlets.

Nikon cancels DL series

13 Feb

Nikon officially dropped the bombshell that it has pulled the plug on three upcoming premium compact camera models that were announced in the first half of 2016 and initially expected to ship in June 2016. This cancellation therefore comes after months of delays as well as rumours of an imminent shipping date.


Nikon DL24-500

Nikon cited electronics hardware problems and low projected profitability in the decision. The cancelled models would have had equivalent focal ranges of 18-50mm, 24-85mm and 24-500mm, making the middle model a direct competitor to Sony’s RX100 line, while the first model covers the focal range of two of Sigma’s DP models (which use prime lenses).


Nikon DL24-85 in silver

Among other things, the cameras would have featured 20fps continuous shooting with autofocus, and in-camera perspective adjustment for architectural photography.


Nikon DL18-50

This is the next major cancellation after Samsung’s withdrawal from the dedicated camera market. Nikon has also announced a voluntary retirement program to lay off 1000 workers.

Yongnuo 85/1.8 with better bokeh, less CA and noisier AF than Canon

12 Feb

For full details, see the video by Christopher Frost, below:


The breakfastographer’s opinion based on the samples shown is that the bokeh is nicer and the CA much lower in the Yongnuo. Corner sharpness is worse, though, and the autofocus has various issues described in the video. No statement was made about focus throw, but it seems to be okay, so manually focusing is an option. At a price of half the Canon, it’s cheaper than a Samyang/Rokinon/Bower/etc., which would also provide only manual focus.

In spite of the corner softness, it’s sold as a full frame lens, and its value proposition as a portrait lens is hard to beat on that format. If you do want to go cheaper, there are 50/1.8 options for APS-C cameras for just over a 100 eurodollars, but bokeh will be better with the 85/full frame combination – or really 85 on any format!

Pentax KP better at high ISO than K-70, especially after DxO PRIME treatment

11 Feb

Imaging Resource have published RAW samples from the Pentax KP. Since I was able to cheat DxO 11 into processing an ISO 102,400 file, I thought I would post the results of performing PRIME noise reduction on a pair of these at ISO 102,400 – one from the KP and one from a K-70 – click on the image for a 1:1 view of the striking difference (KP on left, K-70 on right):


Compare with the out-of-camera JPEG result (KP on left, default in-camera noise reduction on both):


The out-of-camera JPEGs retain a little more detail, along with some more noise – probably a matter of personal taste, but I would go with processed raws here.

The Pentax KP features saturation compensation, to stop colours looking washed out at higher sensitivities. The in-camera processing deals with this gracefully, so that no luminance detail is lost (KP on left, K-70 on right, both with default in-camera noise reduction):


The current version of DxO OpticsPro does not include a Pentax KP profile, and some loss of luminance detail could be seen in the PRIME processed image. As explained by a commenter over on Imaging Resource, this may be due to the KP using a different white point in its raw output compared to previous Pentax cameras. That being the case, it would be true to say that this will not be an issue once the DxO software is updated to support the Pentax KP.

Pentax cameras offer a lot of configurability of the output, and it’s therefore likely that the saturation compensation can be turned off or on as needed.

Overall, one can’t help but conclude that the KP is a huge advance over the K-70, a remarkable camera in its own right. And after initial reserve over the design of the camera, many now seem to be swayed by its rich features, performance and customisability.

Feel free to head over to Imaging Resource for more samples, or take a look at a comparison of the K-70 and Nikon D500 at ISO 102,400, or the post-processed ISO 800k result from a night-time Pentax KP out-of-camera JPEG. Alternatively, read my overall thoughts on the Pentax KP.