Bart,
I just found this thread and while I haven’t played with your tool it looks fantastic! Before I print your target, shoot an aperture series and analyze the images, I have a few questions if you don’t mind.
Hi Hiroshi,
No problem.
- You mention the intriguing possibility of using your tool and an imageJ deconvolution kernel to help with upsampling artifacts. What workflow do you recommend for this? Would you “capture sharpen” then increase the size, and then resharpen? Or only sharpen the final image? How would you build the deconvolution kernels? Only one for the increased size or two separate ones (before and after resizing..?)
Those are indeed the two routes one could take. If we can exactly nail the Capture sharpening, then I would prefer to do that as step one, because it would give a better idea about how far we can go with subsequent Creative sharpening without introducing e.g. clipping. On the other hand, if we e.g. have a high ISO image and we do not want to noise reduce all the life out of it, we could consider postponing the Capture sharpening, and wrap it together into one operation if we already know we are going to enlarge the image. One other consideration is, which upsampling artifacts we may encounter and if correcting them is better done on a sharpened or unsharpened basis.
In general, because I'm a low ISO shooter myself (if possible), I would probably go for separate deconvolution sharpening for Capture, and again when preparing for upsampling+output. I will start another thread about the upsampling workflow where my tool can help to analyse issues and solve some of the softness (it won't create new detail, but it will restore losses).
- I just downloaded the trial version of DxO pro and I am pretty impressed with their lens modules, and how DxO lifts the “veil” of some of my images and restores microcontrast. I wonder if they apply similar methods to build their camera/lens modules?
They essentially do the same, but with many more things being considered. They also differentiate across the image, and thus treat e.g. corners with their specific deblurring. That's why it can take a while before a camera/lens combination is added to the converter solutions that are automatically invoked based on EXIF information. They also calibrate for distance, because lenses do not necessarily perform equally well at all distances.
Viewed in that light, it is amazing how much a single sharpening radius can already restore. For lenses with very poor corner performance one can attempt to do 2 separate deconvolutions, one based on the center of the image and one based on the corners, and then use a radial blend to combine the results in Photoshop. A Raw converter like Capture one already allows to compensate for sharpness fall-off.
- Maybe you should consider setting up a database, so that people who go through the trouble of shooting an aperture series with their favorite camera/lens can deposit the data (and/or the original slanted edge images).
If people want to share their findings, and make a serious effort to follow the guidelines of no-sharpening, a linear tonecurve, and a decent Low ISO exposure conversion (medium grey is medium gray) and contrast is normal (therefore black and white are not clipped), then it can also be useful for others when that info is shared.
I wouldn't mind making an overview when the data is sent to me (link is at the bottom of the tool's webpage).
- I assume the distance at which you shoot the target doesn’t influence the PSF of the camera lens combination (and 25-50x the focal length would be fine and then can be used for all images)
That's correct. the target is 'scale invariant'. In fact that is a major benefit that prevents the need for magnification calibration. The only thing not covered is when lenses perform significantly better/worse at certain distances other than these medium distance settings. Things can be done though for extreme situations like macro, or scanners, or long telelenses. For scanners I use a slide mount with a razor-blade mounted at a slant, and for long distances one can use a larger version of the target (enlarged and deconvolution sharpened,
).
- Lastly, what happens with out of-focus blur/bokeh if you apply your tool
It stays OOF, but becomes a bit less blurred. If the target itself is not optimally focused, then removal of that level of defocus will be attempted. All my tool does, is determine the major blur component, and fit a model to allow removal of that particular blur. Similar but different blur levels will be sub-optimally restored, and there will remain a certain amount of blur if the radius for that blur was larger. If there are fore/background zones with better focus (a smaller radius) then they will be restored with too large a radius and it is likely that sharpening halos will be the result. Therefore it is important to try and focus as good as possible, to find the smallest possible blur radius one could encounter in an image.
Sorry, about these probably naïve questions but I am a newbie when it comes to sharpening.
No, there is no need to be so modest, your questions were excellent and may help others who were wondering but didn't ask.
I just got a D800E, and while I don’t expect that it needs a lot of sharpening in general, the upsizing and diffraction recovery possibilities look vey attractive. Maybe I also convert to the D800 once I will discover that its deconvolved images look as good as the D800E files
Well, the focus is only perfect in a very narrow zone around the focus plane, and there will always be some level of residual lens aberratons and/or diffraction, even on cameras without an AA-filter. And then there is a Demosaicing step which has to make trade-offs between artifacts and sharpness. And then there is resampling, up or down, which will add its own blur. There will always be something to improve, and now we can know how to do that.
Cheers,
Bart
