My Gears have been Ground. I have vented my spleen. And I feel I finally have my arms around the nature of the problem.
The problem is this: Many of the camera review sites post numbers grading various aspects of sensor performance that are for various reasons problematic.
I don't yet have a solution to the problem. All I know is that converting images to TIFF, using in-camera JPG processing, or image downsizing to "normalize" (whatever that means in the context of dynamic range and color depth) all have their problems from an image quality measurement and comparison point of view.
Further, I don't see a way to evaluate if Sony's claim of 15EV+ dynamic range for their A7S is "real" or not. I'm not sure if this small 12mpixel Full Frame sensor-ed device is part of the "Fat Pixel" family of Mythic Pixie Dust cameras. If it is, how might we _see_ or _measure_ the Magic?
Not knowing entirely how to proceed I will set all this aside and go have a long think.
In the meantime, the friend who shared how some standalone Noise Reduction software can work its magic on noisy images suggested something to me. If I had a problem with downsizing A7R images to A7S image size (where the downsized image is _always_ better with large sensored cameras in DxOMark and DPReviews reviews), why not upsize the smaller image to the A7R size?
Hence this blog entry.
Over on YouTube there is a video by a woman who printed a couple A7S images to 47 inches long. That's rather big, right? Is it any "good?" Hmmm...
There's a guy who ran a comparison study with two photographer friends where they tried to see any differences between A7S and A7 (24mpixel) prints. It seems that differences between the A7 and A7S are best seen when comparing identical images. When looking at standalone prints it seems much more difficult to tell which print was made by which camera.
Then there is the ability to upsize images in a somewhat meaningful way. I've been looking at this a little and have to say, the results can be impressive.
There's lots of food for thought, here.
Setup~
- Sony A7S and A7R images downloaded from DPReview
- Rawtherapee
- Adjust Lightness +30
- Adjust Curves by raising the middle
- Capture Sharpen
- Noise Reduce
- Sony A7S image opened in the Gimp
- Upsize from 4240pixels to 7300pixels
- Apply 1pixel USM in upper layer with 70% opacity
Comparison ~
DPReviews base image
Processed image
Comments ~
Let's start by looking at the 2nd, and 5th rows of images. The 2nd row shows the native file size Sony A7R at 100 percent. No noise reduction nor Capture Sharpen were used. When I started this WeeLookSee I thought I might see a clear difference in resolution since the A7R has no AA filter and the A7S does. So if this is as sharp as the A7R is without any further processing, have a close look at row 5.
Row 5 is the A7S image Rawtherapee Capture Sharpened and noise reduced, _then_ upsized 7300pixels long using the Gimp NoHalo algorithm. Pretty amazing, isn't it? Stare at it awhile. Still amazing, right? The most obvious difference to me is in trying to read the "One Way" sign in the middle of the center column of images. Amazing.
Now let's have a look at rows 4 and 6. Row 4 is the native file size A7R image with Rawtherapee Capture Sharpen and noise reduction. We can just begin to be able to read the "One Way" sign. Noise is reduced. The over all image is looking not half bad. Row 6 is the upsized A7S image with a 1 pixel UnSharp Mask applied. While it looks pretty good, it should be obvious that there is more detail in the A7R image.
Lastly, looking at just the A7S upsized images in rows 5 and 6 and not trying to compare them against any of the A7R images, what do we see? They actually look pretty good, don't they?
While I knew it already, this exercise re-enforces to me that software can play an important role in image processing. When done with care, upsizing the 12mpixel A7S to A7R dimensions can yield interesting results.
As I wrap up this blog entry I have to confess that I've had that long hard think. I've thunk a bit. I've cogitated some. I've studied a lot. I've learned a bunch. I've _finally_ found a Vein of Knowledge that is proving rather useful.
Yes, Martha, there is One More Wabbit Hole to fall down.
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