Please add 645D, 645Z sensor size to diffraction calculator

[rfkiii]

if it is deemed necessary. Since the 645D & Z are cropped 645 format, wouldn't it make sense to add this size to the calculator for pixel level diffraction? I think.

[george013]

if it is deemed necessary. Since the 645D & Z are cropped 645 format, wouldn't it make sense to add this size to the calculator for pixel level diffraction? I think.

Basical it's independent of the sensor size. It only depends on the Airy disk formed by the lightcone diafragma-diameter and the image-distance.
Difraction limited is also related to the pixel size of the sensor, not he size of the sensor itself.
Practical you can say that it will be visible if it exceeds the CoC.
The diffraction calculator is based on th F-number. That means only focused at infinity, focal and image distance are the same. As your subject is getting closer, your image-distance is getting larger and so the top-angle of the lightcone smaller. And you will be diffraction limited earlier.
George

[rfkiii]

Thanks for the response but I was referring to the pixel level calculation under the show advanced link.

[Manfred M]

I would suggest that this is likely because this is a site that is very much that serves the amateur / hobbyist photography community and medium format has generally been the domain of professional / commercial photographers. While a few amateurs might own a medium format camera, most of the members shoot crop-frame sensor cameras, although as prices have come down over recent years, a number of us do shoot full-frame cameras.

All this tends to suggest that most of the images in question will remain in digital form and will be displayed on computer screens either locally or posted on the internet. Once you get the medium format, the market tends to be the print, so print size and viewing distance become a far more critical parameters in determining the diffraction limit.

While Pentax has a presence in the "lower end" of medium format (it is still much more expensive than even the top of the line full-frame cameras); why limit it to this specific brand? Why not then the medium format Leica, Hasselblad, Phase One or Leaf cameras and / or backs (as I recall there are a lot of sensor variants here)? To me, this becomes a situation of "diminishing returns" on the time and effort invested in maintaining this data for a very tiny potential audience. The line as to what to support has to be drawn somewhere, and sticking to the camera types most likely used by the members of CiC makes sense and adding medium format seems to be a bit of a stretch.

I'm only a moderator here, and not the site owner, so cannot comment on where Sean will take the site content in the future. I can see why he went as far as he did with this particular tool.

[rfkiii]

I would suggest that this is likely because this is a site that is very much that serves the amateur / hobbyist photography community and medium format has generally been the domain of professional / commercial photographers. While a few amateurs might own a medium format camera, most of the members shoot crop-frame sensor cameras, although as prices have come down over recent years, a number of us do shoot full-frame cameras.

All this tends to suggest that most of the images in question will remain in digital form and will be displayed on computer screens either locally or posted on the internet. Once you get the medium format, the market tends to be the print, so print size and viewing distance become a far more critical parameters in determining the diffraction limit.

While Pentax has a presence in the "lower end" of medium format (it is still much more expensive than even the top of the line full-frame cameras); why limit it to this specific brand? Why not then the medium format Leica, Hasselblad, Phase One or Leaf cameras and / or backs (as I recall there are a lot of sensor variants here)? To me, this becomes a situation of "diminishing returns" on the time and effort invested in maintaining this data for a very tiny potential audience. The line as to what to support has to be drawn somewhere, and sticking to the camera types most likely used by the members of CiC makes sense and adding medium format seems to be a bit of a stretch.

I'm only a moderator here, and not the site owner, so cannot comment on where Sean will take the site content in the future. I can see why he went as far as he did with this particular tool.

Thank you for the reply. I was going to contact Sean directly but there was a suggestion (at some point) to post it here as a better alternative. I was hoping Sean could address this as he gave me a pretty good answer the lest time I asked about the calculator (2008 I believe).

[Black Pearl]

Do you have the camera you are asking to be added and are you having difficulty determining where, when and if you are getting issues with diffraction?

[dje]

Thanks for the response but I was referring to the pixel level calculation under the show advanced link.

rfkiii by all means ask Sean about it but as an interim measure you should be able to get the answer you are after by "fudging" the calculator so that it uses the pixel size of the 645Z which I believe is 5.3 um. With "Set COC based on pixels" checked, select the Full Frame camera option and then put in a MP value that gives a pixel size of 5.3um. (About 31MP seems to give this result.) It doesn't matter that this is a different MP to that of the actual camera as only pixel size is used in the calculation I believe.

Dave

[george013]

What the calculator is doing, is nothing more than comparing the Airy disk to the CoC. In the hidden part you have a choice of setting the print dimensions and the viewing distance, so changing the CoC, And on the "Set circle of confusion* based on pixels" mark you can choice for screen viewing at 100%

George

[rfkiii]

Do you have the camera you are asking to be added and are you having difficulty determining where, when and if you are getting issues with diffraction?

Thanks for your response. I Just acquired a Pentax 645Z. I have not had time to test it visually for diffraction effects which is one of the tests I will perform. Doesn't mean I do not find the D calculator handy. My application for the pixel level diffraction is for cropping. As a normal course of PPing, I may crop very deeply because I was limited by focal length on that particular occasion or when I detect a composition within a composition.

[rfkiii]

rfkiii by all means ask Sean about it but as an interim measure you should be able to get the answer you are after by "fudging" the calculator so that it uses the pixel size of the 645Z which I believe is 5.3 um. With "Set COC based on pixels" checked, select the Full Frame camera option and then put in a MP value that gives a pixel size of 5.3um. (About 31MP seems to give this result.) It doesn't matter that this is a different MP to that of the actual camera as only pixel size is used in the calculation I believe.

Dave

Thanks for your response. I plugged in 91 MPs for a 645 FF sensor which produced the 5.3 micron pixel size and the result seemed logical based on the usual parameters of my work.

[rfkiii]

What the calculator is doing, is nothing more than comparing the Airy disk to the CoC. In the hidden part you have a choice of setting the print dimensions and the viewing distance, so changing the CoC, And on the "Set circle of confusion* based on pixels" mark you can choice for screen viewing at 100%

George

Thank you for your response. I appreciate everyone's time on this matter.

[Polar01]

I do not know if you are interested, however there is a interesting review of the 645 at the following link:
https://luminous-landscape.com/penta...-depth-review/

Cheers: Allan

[rfkiii]

I do not know if you are interested, however there is a interesting review of the 645 at the following link:
https://luminous-landscape.com/penta...-depth-review/

Cheers: Allan

Thanks for the link. Affirms many of my first impressions plus there were some helpful operational and set-up tips included.

Michael Reichmann confuses me. He did a video in August of 2014 or thereabouts (prior to this article) where he was ga-ga about mirrorless and in particular, the Sony A7r. I got the impression he was over heavy cameras. In fact he nearly sold me on getting a Sony A7r (except that I decided to wait for a A7r II - glad I waited).

Here's the link: