Pnetax 645Z Output & Image Quality
**More samples and examples will be available in Part 3, where lenses will also be discussed**
In a word, ‘WOW’. I was not sure what to expect, because there are so many conflicting opinions out there on the web, but most seem to be theoretical i.e. from people who are guessing what 51MP on this sensor means, by extrapolating from their APS-C and FF experiences. While that is understandable, it may not lead you to the most useful conclusion. As you probably know I own a Sony A7R, which has impressed me greatly with its 36MP sensor, so how does the Pentax 645Z compare?
Combined with the best lenses, we see roughly the sort of resolution increase we would expect over the A7R, but there are several additional factors that contribute to the Z impressing quite a bit more than I had anticipated.
Noise & ISO
It is widely recognised that the Pentax 645Z has superb high ISO performance that is significantly above the A7R and, when downsized to match, likely leaves the A7S behind too (the 645z has pixels that are larger than the A7R and more of them). This results in smoother files, a sense of more crisp detail and a richness the A7R cannot match. When it comes to cranking up the ISO, I can shoot a file at ISO 400, work the file hard in LR and end up level with or ahead of where I would have been with an ISO 100 file from the A7R. Shooting high quality landscapes at 800 is not something you even have to question. You just can, which combined with stabilised lenses opens up a whole world of potential. Even ISO 1600 is remarkable and I would not hesitate using this ISO if I needed – It is comparable to three digit ISOs on the A7R on a per pixel basis.
So the high ISO is incredible, but what benefit is there at low ISO?
Noise levels at 100 on the A7R are very low, but you do see benefits shooting at ISO 50, if you are able to accept the loss of some dynamic range. The 645Z at ISO 100 reminds me of the A7R at 50, only with buckets more dynamic range. It is super clean. This is not all that relevant; however, simply because noise levels at 100 on the A7R are not exactly a problem! The main benefit is that you can work the file hard in PP and still end up with very low noise levels. You can take a scene that has a bright flare inducing sky, contrast as flat as a pancake, but backlit, open up the mid tones, bring highlights down, boost shadows, add contrast and still have a beautiful natural looking file that gets you back to your own perception at the time. I have produced images that I know would have taken a tangible technical nose-dive had I shot them on the A7R, yet still marvel at the end result. I can only describe that look as 5×4 film.
I have no idea how it measures and DxO is yet to test this camera, but my perception is that it is appreciably greater than the A7R (and these are the most robust files I have ever used and not by a small margin). Highlights you have to be careful of (as with any camera), but the histogram seems very pessimistic (based on JPEG output of course) and there is lots there in the RAW. I think the internet chatter about having to be careful of highlights with this camera may be due to the histograms being so pessimistic, its hard to know where “RAW reality” is.
On a number of occasions I saw alarming looking histograms, shot quite a few additional exposures and was amazed to find that the first ‘most blown’ frame was often entirely recoverable and looked great. That said, there is so much in the shadows that Exposing To The Right (ETTR) often results in shadows far lighter than you hoped for or want. Considering the DR of this camera and the low noise, even if you expose too conservatively, you are unlikely to end up with anything but a brilliant file that is fit for large prints. I’ll now show some crude examples, just to illustrate the vast reserves this camera has and how this will be useful when shooting into the sun, with hard shadows as a result.
The only downside to this additional DR is that you have to reprogram your brain when looking at unprocessed files. On the LCD they look fine, but once open on the computer they can look quite flat with tonal information in the shadows that goes on and on. This is the reversed equivalent of Ansel Adams’ TriX 320 after water-bath development (because with film we exposed for shadows and managed highlights in processing, whereas with this camera you ensure the highlights are not clipped and shadows can be managed in PP). The bottom line is that a well-exposed file will allow you to manage pretty well any lighting on planet earth and produce whatever result you desire. There is nothing more to want here and, while the A7R was an epic improvement over shooting (and processing) with Canon 5D III, the Pentax is clearly ahead of the A7R. Rarely will you need to dig as deeply as the 645Z allows, but if you do, have confidence that its there in the files!
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