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08-18-2022, 01:38 AM   #1
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Best apertures 67?

Is there any list for typical apertures for the 67 lenses, please?
I try to make one for myself, but for some lenses i dont find any comments.

08-18-2022, 01:50 AM   #2
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If you are used to 35 mm, you can just double the f-number for 67 in general.
08-18-2022, 06:44 AM   #3
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You won't err much using the f/8 to f/16 aperture range for landscape pictures. Here is my experience using a digital Pentax 645Z with a Pentax adapter.

The P67 165 mm f/2.8 can be used starting @ f/5.6. The late version P67 55 mm f/4 can be used at ANY aperture setting. The P67 90-180 mm f/5.6 zoom peaks @ f/8, the same with the M* 300 mm f/4. If you close their diaphragm any more, you are past the peak.

The P67 500 mm f/5.6 still performs admirably @ f/22. The P67 75 mm f/2.8 is excellent starting @ f/4, up to f/16. The P67 100 mm f/4 MACRO peaks @ f/8.
All the newer PENTAX P67 late model lenses perform very well between f/8 and f/16.

Regards

Last edited by RICHARD L.; 08-18-2022 at 07:04 AM.
08-18-2022, 10:19 AM   #4
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Maybe typical is the wrong word.
I just try to make a list for myself to know what is important to know.

---------- Post added 08-18-22 at 11:01 AM ----------

This is a stacked picture (i just learn to do that) from six pictures; it has 25% of 100% now.



---------- Post added 08-18-22 at 11:07 AM ----------

This is the sharpest picture in a row of six moving the focus from the feet till the ears. And it is just not sharp (on f3.5), if there is no fault happen from my side.



This is 100% with f11




And this is a Sony 85mm from two steps away then before on f3.2




If i use the Sony on f1.4 it is less sharper than the best one from my P55 3.5 ... such infos i try to collect for myself. They are unbelievable useless, because all of these pictures will be ok, if i size them down to whatever i need on my website. But i love to make lists ... that's why i have asked for typicall apertures to use with the p67 lenses.


Last edited by Robert9; 08-18-2022 at 11:59 PM.
08-18-2022, 09:36 PM   #5
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What camera are you using them on? It does not sound like it is a medium format camera.

The best aperture will vary with sensor/pixel size as the smaller the pixel is the earlier diffraction will start to limit resolution.

In my first answer I interpreted that you are using a Pentax 67 camera.

Last edited by Fogel70; 08-18-2022 at 10:01 PM.
08-19-2022, 12:03 AM   #6
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Do you think there is a big difference?
I use P67 and 645 on Sony 7R3, 36x24 with 42MP.
08-19-2022, 12:33 AM   #7
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QuoteOriginally posted by Robert9 Quote
Do you think there is a big difference?
I use P67 and 645 on Sony 7R3, 36x24 with 42MP.
Yes. The difference has to do with the sensor size.

08-19-2022, 06:36 AM   #8
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I dont think so. Light meets as a sharp dot or a less sharp circle on the sensor layer. What happens there is another story, but till there, there is no difference in the behaviour of the lens, right?
If we dont have a sharp picture with f2.8, but have one with f8, this will probably be the same on that (not so much) smaller sensor.
08-19-2022, 07:14 AM   #9
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QuoteOriginally posted by Robert9 Quote
...
If we dont have a sharp picture with f2.8, but have one with f8, this will probably be the same on that (not so much) smaller sensor.
At the risk of oversimplifying here, smaller apertures (larger f/no's) typically reduce lens spherical and other aberrations, but increase diffraction effects. So, for a given lens assembly, the size of the physical pixel can change where the best balance is between these two effects. Going from monochromatic to color, the photographic result can be further modified by the Bayer (or whichever pattern is used) color mosaic and its processing algorithms.
08-22-2022, 01:54 AM   #10
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QuoteOriginally posted by Robert9 Quote
I dont think so. Light meets as a sharp dot or a less sharp circle on the sensor layer. What happens there is another story, but till there, there is no difference in the behaviour of the lens, right?
If we don't have a sharp picture with f2.8, but have one with f8, this will probably be the same on that (not so much) smaller sensor.
Let me try and explain where I am coming from and why I came to the conclusion that a larger sensor is more important than pixel size, up to a point anyway. So please bear with me as I explain with the help of hypothetical examples and hypothetic cameras, which will simplify the concept.

Setup:
The selected object is a flat brick wall of which we are selecting a demarcated rectangular space of 3m x 4m (3,000mm x 4,000mm). We have two hypothetical cameras that we will compare against each other, both have sensors with identical pixel pitch, the same aspect ratio as our selected object, and are made by the same manufacturer with similar hardware and software so that the images are manipulated from raw pixel voltage readings to a RAW file in the same way. Camera 1 has a sensor size of 40mm x 30mm and Camera 2 has a sensor size of 400mm x 300mm. The distance from the camera to the wall should be the same which would imply that the focal length of the lenses would be different. For the sake of the discussion we have to assume that the hypothetical lenses have the same optical qualities and distortions.


The Comparison:
Creating a representation of the brick wall onto the camera sensors require a compression of the scene from 4,000mm x 3,000mm to the size of the individual sensors. We can compare the compressions either by measuring the diagonals or surface areas.

Based on surface areas: Camera 1 has to compress the image of the brick wall 10,000 times to fit onto the sensor. Camera 2 only 100 times.

Based on the diagonals: Camera 1 has to compress the diagonal dimension 100 times and Camera 2 only 10 times.

The difference between the MF 51mpx and a FF sensor is difficult to measure unless we apply the same aspect ratio, which would require cropping of at least one of the images. Based on a FF image cropped to 4:3 the image in this example is compressed +/- 60% more than the MF 51 mpx sensor.
Conclusion:
This led me to understand that there are three groups of "components" that determine the quality of the picture. These being (1) the image compression (2) the in-camera processing between pixel voltage readings and the RAW file and (3) the lens.

To me the image base line of quality is the compression of the image. By reducing the image compression we increase the potential of the quality of the picture. (PS. Just in case you lost thread of the discussion: Image compression is not the same as file compression).

Further refinement:
Multiple variations of this comes to mind, such as comparing the compression between MF with large pixels, and APSC with small pixels, while I think the outcome will be an interesting mental exercise yet less practical.

Other factors:
One could argue that compression is improved if a picture is captured on a large sensor with smaller pixels, and I think the evidence we see between the 50mpx and 100mpx sensors with the same physical dimensions supports this.

Practical use:
How does this affect my decisions and what do I want to do with my pictures?

I personally like to print fewer but large prints of the pictures I take and I enjoy being surrounded by large images that take on a realism and the image compression is reversed. So in my use case I should benefit more from a large sensor than a small sensor, regardless of the pixel pitch differences. Pixel pitch also has a practical limit as the pixel sizes near the wavelengths of light. In-camera AI processing can of course alleviate this and then there is also pixel binning, which when combined with AI I am sure can produce fantastic results.

I did consider buying a 100mpx camera as an upgrade for the 50mpx, although being the same sensor size convinced me I will be buying processing features and not improve the baseline of the picture quality. Perhaps I am wrong and I respect everyone's interpretation, so feel free to disagree.

Please share your views, agree or disagree. All appreciated.

Last edited by TDvN57; 08-22-2022 at 11:23 AM. Reason: Finger trouble fixed
08-22-2022, 10:12 AM - 1 Like   #11
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Assume the wall is made of mini-bricks, each of which just fit one detector cell (pixel for the purpose of discussion). The noise in this cell cannot be less than the square root of the number of photoelectrons captured, rms, so the signal-to-noise ratio (S/N) is not less than the square root of the signal photoelectrons. Since a mini-brick maps to a pixel, the larger pixel will have a higher S/N if the f/no was conserved (larger lens objective) to go with the longer focal length (lens is scaled up by a factor of 10 in each dimension) and distances are the same. This implies that the larger pixel size camera will have better S/N and thus potentially greater dynamic range, ignoring other sources of cell noise that might scale with cell size or area. The larger pixels can store 10^2 more photoelectrons for the same well depth.

I like the 645z's dynamic range. This leads me to not be as interested in revising the 645z in the direction of more pixels stuffed into the 44 x 33 focal plane, but rather more pixels to cover the original ~ 60 x 45 (or whatever) focal plane that all but one of our lenses (as I recall) is designed to cover. In other words, a 100 Mpixel focal plane with present 645z cell sizes seems more useful than providing existing field coverage with root 2 higher linear resolution. At least we could eke out more field angle with the 25 mm.

The real-world question, though, is whether a large print of a given field of view landscape taken in daylight with 100 Mp over 44 x 33 will look different than if taken with 100 Mp over 60 x 45 with appropriate change in focal length.
08-22-2022, 11:16 AM   #12
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QuoteOriginally posted by kaseki Quote
Assume the wall is made of mini-bricks, each of which just fit one detector cell (pixel for the purpose of discussion). The noise in this cell cannot be less than the square root of the number of photoelectrons captured, rms, so the signal-to-noise ratio (S/N) is not less than the square root of the signal photoelectrons. Since a mini-brick maps to a pixel, the larger pixel will have a higher S/N if the f/no was conserved (larger lens objective) to go with the longer focal length (lens is scaled up by a factor of 10 in each dimension) and distances are the same. This implies that the larger pixel size camera will have better S/N and thus potentially greater dynamic range, ignoring other sources of cell noise that might scale with cell size or area. The larger pixels can store 10^2 more photoelectrons for the same well depth.

I like the 645z's dynamic range. This leads me to not be as interested in revising the 645z in the direction of more pixels stuffed into the 44 x 33 focal plane, but rather more pixels to cover the original ~ 60 x 45 (or whatever) focal plane that all but one of our lenses (as I recall) is designed to cover. In other words, a 100 Mpixel focal plane with present 645z cell sizes seems more useful than providing existing field coverage with root 2 higher linear resolution. At least we could eke out more field angle with the 25 mm.

The real-world question, though, is whether a large print of a given field of view landscape taken in daylight with 100 Mp over 44 x 33 will look different than if taken with 100 Mp over 60 x 45 with appropriate change in focal length.
I suspect that a lot of AI type of processing takes place between the pixel voltage reading and the raw file. If you just look at the options to determine the color for a given pixel interpreting the Bayer filter, the opportunities for artificial manipulation stands out like a sore thumb. Mix that with AI basics, or perhaps better to call it interpretive evaluation, the result is no longer a direct interpretation of voltage, or an emulation of film.

Thank you for explaning the signal to noise ratio issues, and it certainly adds to my understanding, I think, or at least for the next 10 minutes.

@Focusrite often posts pictures taken with his Credo 60, which is 60mpx over 645 FF with a pixel pitch of +/-6 microns (CCD). If Pentax brings out something like that in CMOS backlit or even a 100mpx in 645 FF I think the results will be great.

Re the lenses for 645 FF, I think three are only two DA lenses, the DA 25mm and DA 28-45mm. The rest are all 645 FF.

.
08-23-2022, 09:23 AM - 1 Like   #13
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QuoteOriginally posted by TDvN57 Quote
I suspect that a lot of AI type of processing takes place between the pixel voltage reading and the raw file. If you just look at the options to determine the color for a given pixel interpreting the Bayer filter, the opportunities for artificial manipulation stands out like a sore thumb. Mix that with AI basics, or perhaps better to call it interpretive evaluation, the result is no longer a direct interpretation of voltage, or an emulation of film.

Thank you for explaning the signal to noise ratio issues, and it certainly adds to my understanding, I think, or at least for the next 10 minutes.

@Focusrite often posts pictures taken with his Credo 60, which is 60mpx over 645 FF with a pixel pitch of +/-6 microns (CCD). If Pentax brings out something like that in CMOS backlit or even a 100mpx in 645 FF I think the results will be great.

Re the lenses for 645 FF, I think three are only two DA lenses, the DA 25mm and DA 28-45mm. The rest are all 645 FF. .
Someone here (I can forget a name in less than 10 minutes) was involved in detector array development, as I recall. He could elaborate on all the other real-life noises that need to be added (in quadrature) to the quantum intrinsic noise.

I have the latter DA zoom; I was fortunate to find a DFA 25mm. My intent was to also use it on film, but sadly the time I can allocate to photographic output has lately been too limited to deal with film also.
08-23-2022, 09:37 AM - 1 Like   #14
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QuoteOriginally posted by TDvN57 Quote
Let me try and explain where I am coming from and why I came to the conclusion that a larger sensor is more important than pixel size, up to a point anyway. So please bear with me as I explain with the help of hypothetical examples and hypothetic cameras, which will simplify the concept.
...

Please share your views, agree or disagree. All appreciated.
Loved your way of thinking about this. I'd just add that I agree on the larger sensors - with an exception: When they have tiny pixels (eg under 4um) they hit the point where the pixel is too darn small they become be useless - the electron well depth gets too low, you lose dynamic range and low light performance.

Last edited by ProfessorBuzz; 08-23-2022 at 09:38 AM. Reason: edit for typo and clarifying too small = useless
08-23-2022, 11:11 AM   #15
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QuoteOriginally posted by kaseki Quote
Someone here (I can forget a name in less than 10 minutes) was involved in detector array development, as I recall. He could elaborate on all the other real-life noises that need to be added (in quadrature) to the quantum intrinsic noise.

I have the latter DA zoom; I was fortunate to find a DFA 25mm. My intent was to also use it on film, but sadly the time I can allocate to photographic output has lately been too limited to deal with film also.
I have the DA 28-45 and have never used the image stabilization, which is adding a lot to its size and weight.

I also came across a DFA 25 a few years ago and grabbed it. This year I got the FA 35mm and I don't think I need the 28-45 anymore. Not sure about that, but I'll see if it stays in the drybox for a year, if so then it is time to let it relocate.

Now I'm ready for a 645FF, which may never come, but who knows.

If Pentax is as smart as they think they are, they'll skip the 645FF and go for the 6x7 digital instead. Then we can move back to the OP's original question. :-)

---------- Post added 2022-08-24 at 02:17 AM ----------

QuoteOriginally posted by ProfessorBuzz Quote
Loved your way of thinking about this. I'd just add that I agree on the larger sensors - with an exception: When they have tiny pixels (eg under 4um) they hit the point where the pixel is too darn small they become be useless - the electron well depth gets too low, you lose dynamic range and low light performance.
I agree with your view of the small pixels. Yet the 100mpx Fuji is doing really well. How much of that is thanks to processing is an open question.
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