I frequently mention that I use Lightroom for most of my raw conversions, and use DxO (tiff output) for my really large prints, stating that DxO has higher quality output for the larger sizes. But I wanted to try to back that up.
So I took this image:
And I converted it to a 16-bit tiff file twice, once in LR and once in DxO. Here is a 200% crop of each:
Lightroom:
DxO:
Both of these remained in 16-bit mode while I cropped and then up-sized using PhotoShop's image size. I only converted to 8 bit at the point where I wrote out the level 12 jpegs.
Now, obviously, the "parameters" for each conversion are not identical. I tried to get them close, but each converter has completely different controls. But I think that the variations in color and brightness notwithstanding, you can still see what I really want to point out, which is this:
Examine the clarity of the white of the eye, the sharpness of the detail in the colored part of the eye, the transition from the white to the colored portion of the eye, the smoothness of the skin, especially in the shadow area under the eye.
In the Lightroom version of the file, there appears to be an underlying "texture" to the image which has nothing to do with the image itself. Kind of a "mottled look". Granted ... we're at 200% magnification here! But that mottled look does not exist in the DxO output. I always see it at high magnifications of LR and even RSP output, but I never see it in DxO output.
Why should I care about a 200% magnification?
Okay, let's think about it ... I have this super duper Canon 5D with a whopping 12.8 megapixels. That means the sensor has 4368x2912 pixels. Now ... at an "ideal" resolution of 300 dpi, what size print will that get me? Go ahead calculate it out, I'll wait.
What?
My 12.8mp camera can only produce a 14.5x9.7" print at 300 dpi? How on earth will I ever get to 18x24"? Or even 20x30"?
At 20x30", my dpi has dropped to only 145 dpi. And that's if I'm lucky enough to get the crop exactly right "in camera" (and to be honest, I generally don't).
So the only way to ever print a 20x30" print, is to double the resolution of the file (i.e. the 200% magnification examples shown above).
Now the good thing is ... nobody ever looks at a 20x30" print so closely that they can see this kind of detail. But I do. And when I have a picture with 70 people in it, I don't want the eyes messed up with mottled patterns, I want the eyes to be clear and sharp.
So there you have it ... that's why I use DxO to process my largest prints. And I output to a 16-bit tiff, because the sooner I drop to 8-bits, and the sooner I switch to jpeg, the more detail I'll lose.
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