So, I was going back and forth between these algorithms, being frustrated about parts of some photos working better with algorithm A, when I felt the total photo looked better with algorithm B or C, when it suddenly dawned on me: why can't we interpolate photos with more than one algorithm? Why is it a choice up front and then you're stuck with it for the total photo? Let alone programs like Lightroom, that don't want to bother you at all with this stuff and don't even give you a choice up front (or 'at all').
Well... I can think up a few reasons why. Good reasons (please read till the end to inform yourself about the possible drawbacks).
But not good enough reasons to hold back my nerdy brain waves.
So I decided to do it.
In the new DNGMonochrome you can interpolate one DNG (the same DNG) with all the provided algorithms.
Different parts can be interpolated differently.
It's quite simple really. Something you could also achieve with an elaborate copy/paste after you interpolated the same photo with three different algorithms.
But my implementation seems simpler.
So how does it work?
First you put the program in 'square mode' by clicking this button (on the right side of the program).
Then, when you move over the photo, you'll notice the hand symbol has changed into a square.
Click anywhere on the photo where you want to use a different algorithm than the original and a square will appear.
Note that currently you can't 'draw' a square. It's just the one click.
Be aware that the initial square is always a fixed size. If you're zoomed in to 400 or 800 percent, the edges of the square won't be visible. You're 'in' the square. Zoom out to actually see it.
Once you placed a square, you can drag it around or change its size. It will already state the original algorithm in the top left corner. Now go back to the dropdown next to the square button, which is now accessible...
... and select the algorithm you want to use in your square. The initial selection will be the same as the original algorithm you used for the conversion.
You can click as many squares as you like. You change the algorithm of the square by selecting it (clicking in it). Selection will show by a thicker edge. If you change the dropdown with multiple squares in the photo, it will always be the selected square (none other) that changes.
Once you're done and want to get back to the regular photo, click the square button again. You'll then be out of 'square mode'. You can still see the squares - faintly blue, and they will retain the algorithm you selected for the square - but you can't move them, select them or change them. For that you have to get back to 'square mode' (by clicking the button again).
You can get rid of the selected square by clicking the 'delete' button, next to the dropdown list.
Some other quick notes:
o When you're in 'square mode' you can still drag the photo (and not the square) by holding down the Shift-key
o Squares will 're-interpolate' when you move them or resize them... they will briefly turn orange
o Squares will 're-interpolate' also in other stages (e.g. when using the noise reduction or right before saving)
o Since this is a first version, bugs will no doubt rear their ugly heads... if the content of the square seems 'off', try to drag it or resize it or delete it and place a new one.
Let me give you an example: ACP is strong on horizontal and vertical edges, since it interpolates along them. As a consequence, it's not very good on diagonals. They tend to look a bit stepped, jagged, not very well anti-aliased. Quite logical if you look at the design of ACP. With VNG it's reversed. That one is quite good on diagonals, but less strong on vertical and horizontal edges, where it tends to zipper. So... do the photo with ACP, and attack any diagonals that bother you with a touch of VNG. Problem solved. Or if you like LMMSE for your noisy photo, but discover some speckles in certain areas, touch it up with VNG or ACP. With a bit of luck, the problem is solved. But well... if you downscale your end result or do not intend to print really large... who's gonna notice anyway? This is all stuff of nerds.
Well, the obvious one... the border of the square is very strict. There is currently no feathering going on (I'm still looking into that possibility). So the biggest risk is that you start seeing the edges of the square in the end result. This might happen especially if the interpolation algorithms are far apart and on very noisy photos. LMMSE for instance, is already quite smooth in its interpolation and leaves less noise behind than the others. If you were to use LMMSE in a square on a noisy photo, done with e.g. ACP, the square might stand out in the end result.
So my advise is to use this system with caution, preferably on small parts of the photo that really benefit from a different algorithm and when interpolating the total DNG with that algorithm isn't preferred. Be especially cautious on high ISO photos.
Another downside: DNGMonochrome doesn't save any type of 'project' file. If you clicked-in 30 squares and are truly happy with them, once you produced your end result and close DNGMonochrome, a next time around your 30 squares will be gone. So a 'redo' is complicated, if not impossible. You'll have to remember what you did. Perhaps in the near future I might introduce some kind of 'project file', to hold on to the state of your labor, but currently there is none.