I've been a PK Sharpener (and now PK Sharpener II) user for many years and love the product.
Until now, I've never had a digital camera that did not have an AA filter, but I am about to receive a Sony A7/R (36 mp sensor with no AA filter).
Does the lack of an AA filter make capture sharpening unnecessary with A7/R, D800e and RX1r files?
If capture sharpening with files from these cameras is necessary, please explain why and which PK Sharpener II capture sharpening setting are recommended for these cameras.
Thanks in advance for you advice.
Jeff Kott
San Francisco
It would be interesting to learn what Jeff Schewe recommends.
Bill,
Thanks for your quick reply. Using PK Sharpener has made me lazy/ignorant regarding sharpening, because I always get such great results using the plug in.
I hate to ask such a basic question, but would you please tell me what visual cues you are looking for on screen at 100% to tell you when you have the proper amount of capture sharpening?
I've been a PK Sharpener (and now PK Sharpener II) user for many years and love the product.
Until now, I've never had a digital camera that did not have an AA filter, but I am about to receive a Sony A7/R (36 mp sensor with no AA filter).
Does the lack of an AA filter make capture sharpening unnecessary with A7/R, D800e and RX1r files?
If capture sharpening with files from these cameras is necessary, please explain why and which PK Sharpener II capture sharpening setting are recommended for these cameras.
I hate to ask such a basic question, but would you please tell me what visual cues you are looking for on screen at 100% to tell you when you have the proper amount of capture sharpening?
Hi Jeff,
It depends on the subject matter in the image whether you'll be able to use visual clues to judge the optimal setting of radius and amount (in that order). If there is a sharp (in the focus plane) edge at a slant, it will be possible to check for the formation of halo artifacts. Without such clues, you can use settings determined earlier, because they will mostly vary only by aperture used. Optimal Capture sharpening is very much a hardware correction, not subject related.
At this point for interested readers it should be noted that there is a divergence of opinion regarding the choice of a proper radius for sharpening between the Bart and the Schewe-Fraser approaches for sharpening. Both agree that the radius is the most critical factor. In Bart's approach, one chooses the radius according to a scientific measurement of the blur radius, where a larger radius is necessary at smaller apertures (larger f/numbers) to take into account the effects of diffraction. In this approach, subject matter is not taken into account. In the Schewe-Fraser approach, the radius is chosen in part according to image content. One uses a smaller radius for images with high frequency image detail such as landscapes and a larger radius for images with lower frequency detail such as portraits, where it is not desirable to image each pore on the subjects nose. The assumption here is that one can selectively enhance certain image frequencies. Further discussion on this matter would be welcome.
Regards,
Bill
I do not think these are competing methods.
The Schewe-Fraser method is asking what do you need from the image.
The Bart method is showing how to get optimal sharpening if it is needed, without making a judgement about the if.
The nature of the Bayer pattern sensor even without an AA filter will still require sharpening. You are still interpolating 2 colors for every color recorded by the sensor. This alone will create a bit of blur. In theory only the Foveon sensor would eliminate this since each color is captured by a separate sensor layer.The Foveon sensor (even without AA filter) will still have an effective sensel area. This area represents a spatial filter with a particular lowpass response (sin(x)/x for a 1-d sensor) that does some attenuation of high frequencies below Nyquist.
Perhaps not competing, but totally different in approach to image quality.
Yes, but IMHO, that's what Creative and Output sharpening is for. Creative sharpening is also much better done with more appropriate tools (spatial frequency targeted and local contrast adjusted), later in the chain of processing activities.
That's right. Just like Raw conversion, Capture sharpening is all about getting an optimal (artifact free, and free of issues that will negatively impact good postprocessing capability) RGB baseline from our Raw capture. That Capture is by definition blurred due to the Capture process itself. The deconvolution sharpening will restore actual scene sharpness, which also improves color accuracy at the pixel level. Using the wrong radius will not do that!
Although the term "Capture Sharpening" has become ingrained in photographic parlance, with the application of deconvolution algorithms it might be better to use the term "image restoration (http://www.clarkvision.com/articles/image-restoration1/index.html)" to denote this process. Application of the unsharp mask does not restore data lost in the capture process, but merely creates the impression of sharpness by the introduction of sharpening halos that accentuate edge contrast. As Roger Clark explains in the above linked article, deconvolution algorithms actually restore details lost in the capture process. This results in an image that more closely approximates the original scene and is relatively free of artifacts. The resulting master image can be further processed by creative and output sharpening to emphasize certain image frequencies.This might seem pedantic, but in my view, no algorithm can "restore lost data". The recorded data can be re-arranged in such a way as to more closely match the (most likely) true scene. If the camera system have a systematic (predictable) loss of high spatial-frequency data, then one can attempt an approximate/regularized inversion of this degradation to come "closer" to the ideal data. This can be done in some mathematical sense (e.g. Least Squared) or subjective sense.
Bill
This might seem pedantic, but in my view, no algorithm can "restore lost data".
It's just like noise reduction or CA correction, it too should be addressed early in the chain of events, preferably in linear gamma space before demosaicing and gamma adjustments break the independent random structure that the noise reduction is based on.
For best results, we recommend starting out with unsharpened files (turn off any sharpening in the scanner or capture software), and using PhotoKit SHARPENER to apply all sharpening.So the question now becomes, do you want to apply capture sharpening at the raw acquisition stage or use PKS II? Depends on your raw processor. Jeff has answered about ACR/LR's sharpening and workflow. You'll have to test this for yourself. I'd vastly prefer to do this at the raw/parametric stage like Jeff and do so now as well. The workflow, the data, the flexibility is all over the map and much depends on your ability to sharpen as early as possible. I also get rendered images from time to time I have to work on and often, they need a dose of PKS Capture Sharpening.
Page 8 of the PKS manual:So the question now becomes, do you want to apply capture sharpening at the raw acquisition stage or use PKS II?
After demosaicing, the data is no longer Raw, but it is blurry. So both PKS and deconvolution are faced with the same challenge, and offer to either increase local contrast (=PKS) or restore resolution (=deconvolution).
This gets to the heart of the matter. While a bit off topic, we are looking for a method to get the best results. Maybe that is provided by a black box software solution, maybe we can go through the process ourselves with a set of basic tools.
So what is the best sequence? Remove noise first?
Then deconvolve, then demosaic,
then gamma,
then the ususal assortment of raw tools?