This is a continuation of a series of posts on the Sony a7RIII. You should be able to find all the posts about that camera in the Category List on the right sidebar, below the Articles widget. There’s a drop-down menu there that you can use to get to all the posts in this series. You can also click on the “a7RIII” link in the “You are here” line at the top of this page.
I’ve been reporting on the effects of Sony’s pixel shift feature in the a7RIII with highly non-real-world targets: Siemens Stars. While such tests have their merits, for some folks there is nothing like taking pictures that look like something you might do if not testing the camera. If you’re one of those people, this post is for you. No numbers. No graphs. Just some images to look at.
I started with this scene:
The fabrics are for false-color comparisons, and the books are useful for noise, and possibly for sharpness, comparisons. I used the Sony Imaging Edge to make ARQ files from each set of four captures and used Raw Therepee to make TIFFs from the ARQs and one ARW (single image) file from each set of four captures. I used AMaZE demosaicing for the single shots, and pixel-shift demosaicing with motion compensation turned off for the ARQs. Then I brought the TIFFs into Lightroom (Lr), and made crops. If it matters, I used an Otus 55 mm f/1.4 lens set to f/5.6, RRS legs, and an Arca Swiss P0 Hybrid head.
Before I could do all that, I had to fight with the Imaging Edge Viewer program, which is what you use to make the ARQ files:
I tried and tried to get Viewer to start. I changed a bunch of Window compatibility settings. This was odd, because it had worked yesterday. Then I renamed the directory that it had last used. When it came up, it couldn’t find that directory, and the errors stopped. probably there is some file in what had been the last-used directory that was causing Viewer to choke. Not very defensive programming on the part of Sony.
Here’s a falsely-colorful crop from one of the single shots:
And the four-shot stack:
That looks really good.
Here’s another pair:
I’ll bet you don’t have any difficulty telling which is which.
Here’s a pair where I looked at a Fan Ho book that has a coarsely-woven binding.
Now I’m going to stay on that part of the scene and show you what happens when you underexpose and push in post.
First, a 3-stop underexposure:
Not only is the moire reduced by the stacking, the dynamic range is improved. This is not surprising given the fact that four times as many photons gave their lives making the four-shot stack than perished in any one shot.
Let’s look at a 7-stop underexposure:
The stacked image is a big improvement.
What if we average the 4 demosaiced images, with no pixel shifting. Turns out there’s an easy way to do that in Raw Therapee (Thanks, ogniw):
You can see that we get even more noise reduction, but we’ve lost sharpness.