Mike Davis

Lives in United States Dallas, TX, United States
Has a website at http://www.accessz.com
Joined on Jun 12, 2002

Comments

Total: 93, showing: 1 – 20
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In reply to:

Josh Leavitt: I'm terrified to think about how much the lenses will cost that can sharply resolve 150MP across their full aperture range. Pretty awesome nonetheless, though.

@mosc Excellent - your hunch matches my math, exactly.

100 MP (11545x8659 pixels) from a 44x33mm sensor gives us a pixel density of 262.4 pixels/mm, which translates to a maximum f-Number of f/8.0 to prevent diffraction from inhibiting a desired print resolution of 5 lp/mm at the enlargement factor had when resizing the image to 360 ppi without cropping or resampling. (Reduce your desired print resolution by a factor of two, to 2.5 lp/mm. and you can shoot at f/16.)

150 MP (14140x10605 pixels) from a 55x41mm sensor gives us a pixel density of 257.7 pixels/mm, which translates to a maximum f-Number of f/8.1 to prevent diffraction from inhibiting a desired print resolution of 5 lp/mm at the enlargement factor had when resizing the image to 360 ppi without cropping or resampling. (Reduce your desired print resolution by a factor of two, to 2.5 lp/mm. and you can shoot at f/16.2.)

Link | Posted on Apr 3, 2017 at 21:22 UTC
In reply to:

Mike Davis: With equivalent Pixel Count, Print Size, and Viewing Distance...

... and looking only at the impact on DoF and Diffraction...

Small Sensors can give us the same DoF and diffraction as larger sensors, but with the faster shutter speeds had with smaller f-Numbers.

Large Sensors can give us the same DoF and diffraction as smaller sensors, but with the slower shutter speeds had with larger f-Numbers.

It's the higher enlargement factor required by a small sensor which has the same pixel count as a larger sensor, that forces use of smaller f-Numbers to secure smaller Airy disks at the sensor before magnification, to produce like-sized prints with like-sized Airy disks and like-sized CoCs after enlargement.

Thus, small sensors don't have a DoF advantage or a diffraction disadvantage - they only have a shutterspeed advantage.

www.apug.org/forum/index.php?threads/exposure-times-for-4x5.137760/#post-1901328

Link | Posted on Mar 23, 2017 at 19:39 UTC
In reply to:

Mike Davis: With equivalent Pixel Count, Print Size, and Viewing Distance...

... and looking only at the impact on DoF and Diffraction...

Small Sensors can give us the same DoF and diffraction as larger sensors, but with the faster shutter speeds had with smaller f-Numbers.

Large Sensors can give us the same DoF and diffraction as smaller sensors, but with the slower shutter speeds had with larger f-Numbers.

It's the higher enlargement factor required by a small sensor which has the same pixel count as a larger sensor, that forces use of smaller f-Numbers to secure smaller Airy disks at the sensor before magnification, to produce like-sized prints with like-sized Airy disks and like-sized CoCs after enlargement.

Thus, small sensors don't have a DoF advantage or a diffraction disadvantage - they only have a shutterspeed advantage.

No thanks. I've tangled with you plenty of times in the past. Anybody with any measure of experience knows that large format cameras suffer longer exposures to achieve equivalent DoF in like-sized prints. Small formats have a speed advantage. Get over it.

Link | Posted on Mar 22, 2017 at 10:21 UTC
In reply to:

Mike Davis: With equivalent Pixel Count, Print Size, and Viewing Distance...

... and looking only at the impact on DoF and Diffraction...

Small Sensors can give us the same DoF and diffraction as larger sensors, but with the faster shutter speeds had with smaller f-Numbers.

Large Sensors can give us the same DoF and diffraction as smaller sensors, but with the slower shutter speeds had with larger f-Numbers.

It's the higher enlargement factor required by a small sensor which has the same pixel count as a larger sensor, that forces use of smaller f-Numbers to secure smaller Airy disks at the sensor before magnification, to produce like-sized prints with like-sized Airy disks and like-sized CoCs after enlargement.

Thus, small sensors don't have a DoF advantage or a diffraction disadvantage - they only have a shutterspeed advantage.

Wrong.

Link | Posted on Mar 22, 2017 at 00:59 UTC

With equivalent Pixel Count, Print Size, and Viewing Distance...

... and looking only at the impact on DoF and Diffraction...

Small Sensors can give us the same DoF and diffraction as larger sensors, but with the faster shutter speeds had with smaller f-Numbers.

Large Sensors can give us the same DoF and diffraction as smaller sensors, but with the slower shutter speeds had with larger f-Numbers.

It's the higher enlargement factor required by a small sensor which has the same pixel count as a larger sensor, that forces use of smaller f-Numbers to secure smaller Airy disks at the sensor before magnification, to produce like-sized prints with like-sized Airy disks and like-sized CoCs after enlargement.

Thus, small sensors don't have a DoF advantage or a diffraction disadvantage - they only have a shutterspeed advantage.

Link | Posted on Mar 21, 2017 at 22:53 UTC as 272nd comment | 7 replies
In reply to:

Mike Davis: With the older Sky HDR, 2 exposures are made, roughly 3 seconds apart and thus, any subject motion that occurs within the user-specified overlap zone can make the final blend useless. Both the camera and everything in the scene must remain motionless for both exposures - at least within the overlapped portions of the frame. Adding a third exposure with this new app increases the risk of motion-related failure.

Another issue with Sky HDR that would only be made worse with this new app, is the time required, looking through the viewfinder.

In bright sunlight, the LCD display is inadequate for such editing and even a WiFi-associated iPad would be cumbersome and compromised in bright sunlight, so you're pretty much confined to looking through the EVF while adjusting the settings. THAT gets old, very quickly, if the camera isn't conveniently positioned at eye level and aimed more or less level with the horizon or downward.

In other words, Sky HDR and this newer 3-exposure version, would be much easier to use if Sony or some other manufacturer offered a variable-angle viewing attachment for the a6000. (Perhaps something is already available for the other Sony cameras supported by these apps.) Seriously, just try using Sky HDR in bright sunlight, with the camera shooting from an up-angled position any lower than chest height. You'll have to contort yourself into positions you didn't think possible, for several minutes at a time.

All that said, the results can be amazing - especially if you make the poorly labeled "defocus range" really thick, so that the transition between the two exposures is all the more undetectable - which, however, only increases vulnerability to subject motion between the two exposures.

Link | Posted on Mar 20, 2017 at 14:18 UTC

With the older Sky HDR, 2 exposures are made, roughly 3 seconds apart and thus, any subject motion that occurs within the user-specified overlap zone can make the final blend useless. Both the camera and everything in the scene must remain motionless for both exposures - at least within the overlapped portions of the frame. Adding a third exposure with this new app increases the risk of motion-related failure.

Another issue with Sky HDR that would only be made worse with this new app, is the time required, looking through the viewfinder.

In bright sunlight, the LCD display is inadequate for such editing and even a WiFi-associated iPad would be cumbersome and compromised in bright sunlight, so you're pretty much confined to looking through the EVF while adjusting the settings. THAT gets old, very quickly, if the camera isn't conveniently positioned at eye level and aimed more or less level with the horizon or downward.

Link | Posted on Mar 20, 2017 at 14:18 UTC as 1st comment | 1 reply
On article Google AI adds detail to low-resolution images (150 comments in total)
In reply to:

Biowizard: I'll believe this when Google provides a web page where I can upload an arbitrary 8*8 pixel photo reduction, and get something back that vaguely resembles my original photo. Until then, it's unproven snake oil.

Brian

@Biowizard Yes, and can they do it without reliance on higher resolution versions of the images already known to Google - the first step of their two-step approach?

Send them a photo of a coin held between someone's thumb and forefinger, rendered at a resolution similar to the samples shown above, then see if Google can recover the coin's year of issue.

Link | Posted on Feb 10, 2017 at 18:08 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

Thanks for stating that, explicitly. It makes misinterpretation less likely.

And thus, you're saying the same thing I said with this equation:

f -Number = 1 / desired print resolution in lp/mm / anticipated enlargement factor / 0.00135383

Rearranged:

Print resolution in lp/mm = 738.645 / (f-Number * anticipated enlargement factor)

Note the absence of any variable for pixel count or pixel density.

We really are in agreement. It only looks as if we aren't when qualifications are omitted or ignored as we try to use the English language to convey scenarios.

Link | Posted on Jan 26, 2017 at 07:05 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

But what display size and what viewing distance?

Link | Posted on Jan 26, 2017 at 03:08 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

You've not stated a print size and viewing distance for your comparison scenario, above. This makes your contention impossible to prove. Really, all you've given us is yet another example of people talking apples and oranges for failure to fully qualify their contentions.

Link | Posted on Jan 25, 2017 at 22:58 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

Correcting my second to the last comment, above, in the interest of accuracy...

The first paragraph should read as follows:

It's the higher enlargement factor required by small, high-density sensors having the same pixel count as larger sensors that forces the use of *larger* apertures (*smaller* f-Numbers), *to yield* smaller Airy disks at the sensor before magnification, to produce like-sized, like-resolution prints.

Link | Posted on Jan 25, 2017 at 13:18 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

We're saying the same thing, and now you are qualifying your statements nicely.

Link | Posted on Jan 24, 2017 at 17:29 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

It's the higher enlargement factor required by small, high-density sensors having the same pixel count as larger sensors that forces the use of smaller apertures (larger f-Numbers), and thus, smaller Airy disks at the sensor before magnification, to produce like-sized, like-resolution prints.

In the end, neglecting any discussion of SNR or other traits, looking only at the impact had on DoF and diffraction, small sensors can do everything the large sensors can do, but they leave us with fewer diffraction-free f-Numbers from which to choose, forcing us to shoot closer to wide open, which yields faster shutter speeds for a given amount of light and ISO setting.

Link | Posted on Jan 24, 2017 at 14:52 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

With equivalent Pixel Count, DoF, Diffraction, Print Size, and Viewing Distance...

Small, high-density sensors can give us the same DoF and diffraction as larger sensors, but with faster shutter speeds at smaller f-Numbers, and thus, confining the photographer to fewer "diffraction-free" f-Numbers from which to choose, of those offered by any given lens.

Large, low-density sensors having the same pixel count, can give us the same DoF and diffraction as smaller sensors, but with slower shutter speeds at larger f-Numbers, and thus, more "diffraction-free" f-Numbers from which to choose, of those offered by any given lens.

Link | Posted on Jan 24, 2017 at 14:52 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

"Pixel count has no effect on diffraction. More pixels resolve more detail than fewer pixels stop-for-stop."

This is true when the pixel count is increased while shooting at the same f-Number and maintaining the same viewing distance - without simultaneously increasing the print size.

People with 50 MP sensors will, at the very least, be tempted to make larger prints than they would make with like-sized, 20 MP sensors. If they do make larger prints, the Airy disks produced at any given aperture will suffer the same increase in enlargement factor.

The f-Number at which diffraction will begin to inhibit a desired print resolution, in line pairs per mm, can be calculated as follows:

f = 1 / desired print resolution in lp/mm / anticipated enlargement factor / 0.00135383

Thus, as pixel density increases, all else remaining equal, there's no increase in vulnerability to diffraction. (What Great Bustard said...) Nothing I wrote in my original comment contradicts this.

Link | Posted on Jan 24, 2017 at 14:52 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

Increase the print size and the viewing distance proportionately (can you enforce this?) and you'll still have to avoid stopping down below f/11.1. Decrease the print size by a factor of two (from 22.93x17.2 to 11.46x8.6 inches), without changing the viewing distance, and you can stop down to f/22.2 for additional DoF, while still delivering subject detail to 5 lp/mm. Reduce your resolution and/or viewing distance requirements and you can make any size print you like.

I don't feel sorry, so much, for Phase One or Hasselblad, but the Pentax 645z has almost the exact same specs, in terms of pixel count, sensor size and, thus, pixel density.

There's much more to choosing a camera than pixel math can dictate and this FujiFilm offering is busting at the seams with nice features. Pentax must be crying.

Link | Posted on Jan 22, 2017 at 15:02 UTC
In reply to:

Mike Davis: With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

For this 51.1MP sensor, at 188.4 pixels/mm, the maximum permissible 5 lp/mm print size is 22.93 x 17.2 inches (great for a 13x19-inch printer, with room for cropping) AND any f-Number up to f/11.1 can be used without concern for diffraction inhibiting 5 lp/mm subject detail. Double the viewing distance from 25cm to 50cm (can you enforce this?) without changing the print size and you can stop down two additional stops for additional DoF - as far as f/22.2 - as the print resolution falls to 2.5 lp/mm, thanks to diffraction, but looks just as detailed from twice the distance.

Link | Posted on Jan 22, 2017 at 15:01 UTC

With 8256x6192 pixels on a 43.8x32.9mm sensor, I've calculated a pixel density of 188.4 pixels/mm, which falls below my long-held opinion that, ideally, sensors should never exceed a maximum of 200 pixels/mm, lest the cameras suffer an inadequate range of f-Numbers at which diffraction will support true subject detail resolution of 5 lp/mm (in a non-resampled, uncropped, 360 dpi final print from a CMOS sensor, where the RGBG Bayer algorithm and AA filter will reduce a pixel count-implied resolution by 30%), to support a viewing distance as close as 25cm (9.84 inches).

Link | Posted on Jan 22, 2017 at 15:00 UTC as 8th comment | 18 replies

As theaters slowly converted to digital projectors, it was the motion picture industry that prolonged the demise of Kodak film production, well after the majority of roll film still photograghers had rushed into digital cameras.

Interestingly, we can now thank the interest of analog-loving cinematograghers for Ektachrome's resurrection - first, in 35mm motion picture stock, ahead of still photography roll or sheet films.

http://motion.kodak.com/motion/customers/productions/default.htm

Link | Posted on Jan 6, 2017 at 15:06 UTC as 45th comment
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