Beginner's question on sharpening

[ErikKaffehr]

Hi,

Masking doesn't sharpen areas without edges. Sharpening always enhances noise. So, if you have a noise free image neither masking nor noise reduction are needed.

With the Alpha 99 I have right now and also with the P45+, I feel noise is much less an issue than before.

Luminance noise reduction reduces sharpness, color noise reduction much less. The P45+ has a lot of shadow noise, so I feel some color noise reduction is good to have. On the Alpha 99, I don't know…

Best regards
Erik

hai Erik,  I use ACR and it looks the same..

on a d810 at base iso i never use masking ( =0)  
Also i do not use any  ( chromatic) noise reduction      (i use only color noisereduction at high iso at 15 %)

Can you explain to me what is the benefit of both for you?

[bjanes]

Also, the lens used as mentioned has much to do with all this. This paired with the pixel pitch of the sensors.  More current digital Apo Macro lens I use starts diffraction at F18 or 22. Many others much sooner.

Diffraction limits the resolution at all apertures, but when we say that a lens is diffraction limited at a certain f/stop, this means that its resolution is limited only by diffraction rather than aberrations, beginning at that aperture. A lens that is diffraction limited at f/18 or f/22 is not a well performing lens as shown by the limiting resolutions shown in the table below. A MTF50 of 35 lp/mm is not impressive for a dSLR or MFDB, but it would be OK with an 8 x 10 inch view camera. With such a lens, aberrations predominate at larger apertures and the potential loss of resolution due to stopping down is not that apparent until the aperture is small enough to eliminate the predominant effects of aberrations. With an excellent lens, loss of resolution from stopping down is apparent not far from the maximum aperture.



The effect of diffraction is independent of pixel pitch, and for a given aperture, there is no loss of system resolution with a finer pixel pitch.  However, if you want to make use of the increased resolution offered by a fine pixel pitch you shouldn't stop down so that the diffraction spot (Airy disc) is more than approximately twice the pixel size (assuming a Bayer array sensor). These concepts are well reviewed here.

Regards,

Bill

[Phil Indeblanc]

It sounds like I have to read this a couple times and the link provided. Thank you for them.....

But, I'm not sure YET, what this means in usage. Maybe you are correcting my terminology in using deffraction vs aberration? Here is my observation....
I use both a current macro digi Schneider and Rod lenses with use on a 11mircon pixel on 4x5 and with a loop I can see the focus get fuzzy beyond ~F22.
I was under the impression that this is deffraction caused by reflective circles of confusion due to the blades shape of the shutters?  I maybe off, but its what I remember when working and reading up on this and testing things out. My memory works less and less like digital device every year :-)

[Bart_van_der_Wolf]

It sounds like I have to read this a couple times and the link provided. Thank you for them.....

But, I'm not sure YET, what this means in usage. Maybe you are correcting my terminology in using deffraction vs aberration? Here is my observation....
I use both a current macro digi Schneider and Rod lenses with use on a 11mircon pixel on 4x5 and with a loop I can see the focus get fuzzy beyond ~F22.
I was under the impression that this is deffraction caused by reflective circles of confusion due to the blades shape of the shutters?  I maybe off, but its what I remember when working and reading up on this and testing things out. My memory works less and less like digital device every year :-)

Hi Phil,

At f/22, the diffraction pattern diameter for Green light (which is the dominant contributor to Luminance resolution) of e.g. 555 nanometer wavelength, is 2.44 x 0.555 x 22 = 29.8 micron. That means that the finest detail is blurred by diffraction alone to a size that's more than 2 (11 imicron pitch) pixels in diameter. Added to that is the blur that is caused by residual lens aberrations. So I'm not surprised that you could see that with a loupe, it's as expected from the laws of physics.

You'll be able and see the image get fussy at wider apertures already if you use smaller pitch sensels. Smaller pitch sensels can pick up deterioration from smaller diffraction blur diameters more accurately, and thus at wider apertures.

Cheers,
Bart

[bjanes]

It sounds like I have to read this a couple times and the link provided. Thank you for them.....

But, I'm not sure YET, what this means in usage. Maybe you are correcting my terminology in using deffraction vs aberration? Here is my observation....
I use both a current macro digi Schneider and Rod lenses with use on a 11mircon pixel on 4x5 and with a loop I can see the focus get fuzzy beyond ~F22.
I was under the impression that this is deffraction caused by reflective circles of confusion due to the blades shape of the shutters?  I maybe off, but its what I remember when working and reading up on this and testing things out. My memory works less and less like digital device every year :-

Phil,

I see that Bart has already commented regarding the effects of the size of the Airy disc with respect to 11 micron pixels. I am confused as to what system you are using. You mention 4x5 (?inch) and 11 um pixels, but there are no 4x5 inch digital sensors. 35 lp/mm resolution looks much better with 4x5 inch than 24x36 mm, since the latter image needs more magnification for a given print size.

Regards,

Bill

[Phil Indeblanc]

The explanation sounds factual Bart, yet perhaps the results would be backpedaling with smaller pixels...Or I'm misunderstanding?
We are trying to achieve more sharpness/more dof,

Smaller pitch sensels can pick up deterioration from smaller diffraction blur diameters more accurately, and thus at wider apertures.

So should I gather from this that for someone looking to stop down more/high F without deffraction in order to get more DoF, smaller pixels is NOT the answer, but on the contrary.


Yes Bill, the 4x5 is regarding the "tunnel". Somewhere I mentioned its a 22mpixel MFDb.

there is no loss of system resolution with a finer pixel pitch

With smaller pitch is the DoF increased or decreased?  I think at this point another factor plays in the mix, and that is resolution. Take a finely polished 35cm marble for example, and try to fill the frame of a 22mp Db. Then take a 40mp Db on same setup, and try filling that frame...By physics, would they have the same DoF? But the 40mp having the 18mp added size in output?

(Can you tell I have yet to read that link :-)

[ErikKaffehr]

Hi,

If you look at an enlargement of given size, DoF is not dependent on pixel size, nor is diffraction.

Smaller pixels will allow better sharpening, so it may be possible to compensate for diffraction better with smaller pixels.

On the other hand, it is conceiveable to print larger with smaller pixels, and with a larger print size the CoC on sensor needs to be smaller. Larger prints are more demanding.

Simply enough, smaller pixels are benefitial, except that DR will be slightly better with larger pixels and the raw files will be larger with smaller pixels.

Best regards
Erik

The explanation sounds factual Bart, yet perhaps the results would be backpedaling with smaller pixels...Or I'm misunderstanding?
We are trying to achieve more sharpness/more dof,
So should I gather from this that for someone looking to stop down more/high F without deffraction in order to get more DoF, smaller pixels is NOT the answer, but on the contrary.


Yes Bill, the 4x5 is regarding the "tunnel". Somewhere I mentioned its a 22mpixel MFDb.
With smaller pitch is the DoF increased or decreased?  I think at this point another factor plays in the mix, and that is resolution. Take a finely polished 35cm marble for example, and try to fill the frame of a 22mp Db. Then take a 40mp Db on same setup, and try filling that frame...By physics, would they have the same DoF? But the 40mp having the 18mp added size in output?

(Can you tell I have yet to read that link :-)

[Phil Indeblanc]

that helps. So I understand Bart and Bill in this, just that they were not what I was hoping to hear :-)

I guess your saying this makes sense...that DoF nor defraction, is effected by pixel size. Once you factor in distance and focal I think it makes a difference....
As in.... If you have a subject at X distance, and use a zoom to get frame fill of the subject with a smaller pixel sensor(yet high resolution), vs that same subject with less zoom, but camera closer to subject to fill frame with larger pixel sensor(somehwat lower resolution), I'm pretty surer the high resolution with smaller pixels will have more DoF. I think that was my findings when testing this.

So I take it the sensor makers got all the issues with overlay lenses resolved with the color bleeding issues and such.
So the new crop of sensors prove to do a better job than the 22mp 11micron chips from years ago....I think we are down to 4-6micron chips these days, right? At least in PhaseOne backs and maybe comparable to Sony 36mp pixel size?

I hope this info is helping the OP. It is helping me clarify things that have started to get foggy, and now clear:-)