Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-20-2008, 04:25 AM   #31
Veteran Member




Join Date: Jan 2008
Location: Seattle, Washington, USA
Photos: Gallery
Posts: 812
QuoteOriginally posted by Katsura Quote
I do not agree.

Maybe it's because I'm more sensitive to flickering, but I can distinctively tell the difference between a monitor set to 60Hz refresh rate and 90, I can also tell the diff between 60 and 70 and 85, above 85 I can no longer tell the difference.
I'll go along with Katsura on this one; I readily detect CRT monitor flicker below 75 Hz refresh rates, and usually have mine set at 85 Hz to reduce the annoyance to insignificance.

02-20-2008, 06:50 AM   #32
Senior Member
amateur6's Avatar

Join Date: Mar 2007
Location: Rhode Island
Photos: Gallery
Posts: 177
Original Poster
QuoteOriginally posted by christinelandon Quote
I'll go along with Katsura on this one; I readily detect CRT monitor flicker below 75 Hz refresh rates, and usually have mine set at 85 Hz to reduce the annoyance to insignificance.
I'm obviously about to compare apples to oranges, but -- you must be REALLY annoyed when you go to the movie theater, then: as m80 pointed out in his first post, cinema is "only" 24 fps.



Obviously there's a difference between the refresh rate of a monitor and the persistence of vision of an image reflected off a screen, but the fact remains that 24 fps can fool the brain (firmware NOT hardware) into thinking it's seeing motion. Of course, the other thing to consider is that those images were PRODUCED at 24 fps, and the resultant blur of objects in motion certainly helps the illusion.

[edit: I'm still reading them, but I just found additional authoritative sources: Cameras and Eyes
Standardized Human Eye
The Rods and Cones of the Human Eye

Last edited by amateur6; 02-20-2008 at 08:47 AM. Reason: new info discovered
02-20-2008, 01:48 PM   #33
Senior Member




Join Date: Nov 2006
Location: Los Angeles
Posts: 193
QuoteOriginally posted by Peter Zack Quote
It would take some searching and I don't have the time but a good digital camera has a dynamic range of 5 stops, and average scene has a dynamic range of 10 stops and the human eye has a range of 20 stops...
Are you sure about this?

I've read from several sources and even talked to Joe McNally once about DR and my understanding is the following:

Approx:

20-22 stops of Dynamic Range in the human eye
9-14 stops of Dynamic Range in a DSLR
5 stops of Dynamic Range on printed paper.

Roughly its 20 > 10 > 5 from eye to paper.

Maybe I'm wrong but I was quite sure this was right.
02-20-2008, 04:58 PM   #34
Veteran Member
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,871
QuoteOriginally posted by alinla Quote
20-22 stops of Dynamic Range in the human eye
9-14 stops of Dynamic Range in a DSLR
5 stops of Dynamic Range on printed paper.

Roughly its 20 > 10 > 5 from eye to paper.

Maybe I'm wrong but I was quite sure this was right.
I've given the numbers somewhat up in this thread. The eye is anything between 6.5 f-stops to 20 f-stops depending on how much time to give it to adapt (4ms only, 4s, or 30 min!).

It is EASY to beat the eye, technically, but it is DIFFICULT (still impossible) to build a camera which can fool the eye (making it believe it sees a real scenery).

02-20-2008, 05:09 PM   #35
Veteran Member
ve2vfd's Avatar

Join Date: Aug 2007
Location: Montreal, Canada
Photos: Gallery
Posts: 2,433
No thread about the human eye can be complete without "Rods and Cones"!!!

YouTube - Rods & Cones

(What can I say? I'm a hard core Blue Man Group fan!!!

Pat
02-20-2008, 10:10 PM   #36
Pentaxian
Moderator Emeritus




Join Date: May 2007
Location: Edmonton Alberta, Canada
Photos: Gallery | Albums
Posts: 10,643
You may be right as the newer sensors are getting better without a doubt in this area.

QuoteOriginally posted by alinla Quote
Are you sure about this?

I've read from several sources and even talked to Joe McNally once about DR and my understanding is the following:

Approx:

20-22 stops of Dynamic Range in the human eye
9-14 stops of Dynamic Range in a DSLR
5 stops of Dynamic Range on printed paper.

Roughly its 20 > 10 > 5 from eye to paper.

Maybe I'm wrong but I was quite sure this was right.
02-23-2008, 06:12 PM   #37
Site Supporter
Site Supporter
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 17,869
For all those who are interested, I referenced one of my father's engineering books from the 1940's
" The Scientific Basis for illuminating engineering" by Moon. When I was in university, this book was still well known to the professor I had teaching the same subject.

In the book, there is a nice little graph that shows the average area of the pupil, adjusted to level of light.

at 10e-6 lumens/sq foot, the area of the pupil is 50 square millimeters, and at 2000 lumens per square foot it is about 3 square mm.

This gives 2 interesting points, the range of apatures and the overall working range of the eye. The working range is a ratio of 2 billion to 1, or about 31 stops total range.

if we consider the change in area the eye can stop down 6 stops this means the cornea is good for a dynamic range of something like 25 stops.

There is also discussion about resolving power of the eye, with different tests. the eye can resolve 2 stars at 1 minute of arc, 2 black bars on white background at 1/2 minute of arc, or a vernier scale (multiple bars) at .15 minutes of arc. Here they state the typical spacing of the cone receivers in the eye is about 3 microns.

Focal length is also noted at 15mm

OK guys, now that you have some real data go at it.


Last edited by Lowell Goudge; 02-23-2008 at 06:44 PM.
02-23-2008, 08:21 PM   #38
Veteran Member
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,871
QuoteOriginally posted by Lowell Goudge Quote
at 10e-6 lumens/sq foot, the area of the pupil is 50 square millimeters, and at 2000 lumens per square foot it is about 3 square mm.

This gives 2 interesting points, the range of apatures and the overall working range of the eye. The working range is a ratio of 2 billion to 1, or about 31 stops total range.

if we consider the change in area the eye can stop down 6 stops this means the cornea is good for a dynamic range of something like 25 stops.
Thanks for the data. It nicely adds to the data I forwarded higher above.

I believe, though that the 2 billion to 1 ratio is not used today anymore, seems to be more like 1 million to 1 (20 f-stops), as I have mentioned above. Now let's combine this:

Iris ratio 50:3 or 4 f-stops. Let's be generous and say 4.5 f-stopy
The eye's static contrast ratio: 6.5 f-stops
Makes a combined DR of 11 f-stops.

The remaining 9 f-stops then must come from the chemical adaption of the retina to darkness which takes up to 30 min to complete.

Otherwise speaking:
Combine a dynamic illumination of 9 f-stops with images exhibiting 11 f-stops DR and the eye should be fooled. Of course, switching from 2 to 1000 lumens backlight brightness when switching images will not please everybody
02-24-2008, 08:44 AM   #39
Veteran Member




Join Date: Nov 2007
Location: Binghamton, NY, USA
Posts: 643
QuoteOriginally posted by m8o Quote
Under Focal Length of the Eye he writes "...50 is totally absurd..."

Here is a simple test I want everyone to try. All you need is a zoom that starts in the 30mm range and ends around the 70mm mark. Wider is fine.

A) find an object with high perspective. A chair viewed from 30 - 45 degrees and 20 to 30 degrees down is perfect. Anything with 'perspective' will do. Just don't look at a white wall perpendicular to it no less.

B) Look through the viewfinder at the object with one eye, and keep the other eye open also looking at it.

C) zoom in and out with the lens.

D) notice how the same object shrinks and expands relative to the naked eye. You may even notice a shift of the perspective of the lines of the object (need wider zoom to really notice that)

E) Stop moving the lens barrel when the two views of the object through the two eyes are identical.

F) Note the focal length on the barrel of the lens.

The lens is at or darn close to 50mm, isn't it... A tiny bit under is likely I'd say.

-steve
uhm.. one slight issue with this. ~50mm is the human eye PERSPECTIVE, not it's FOV. think of it this way. focus on the center of the monitor and see if you can see your elbows, without changing your focus. i don't think this would be possible with a 50mm FOV.
02-26-2008, 04:11 AM   #40
Senior Member
amateur6's Avatar

Join Date: Mar 2007
Location: Rhode Island
Photos: Gallery
Posts: 177
Original Poster
QuoteOriginally posted by OniFactor Quote
uhm.. one slight issue with this. ~50mm is the human eye PERSPECTIVE, not it's FOV. think of it this way. focus on the center of the monitor and see if you can see your elbows, without changing your focus. i don't think this would be possible with a 50mm FOV.
Yeah, that's probably the biggest issue with comparisons like this (and why I didn't ask about focal length -- in the two ways it can be determined to have equivalents, it's been done to death).

On the other hand, close one eye -- you certainly can't see BOTH elbows, now (unless you have no nose).

Regardless, it was a fun little discussion while it lasted!
02-26-2008, 07:51 AM   #41
m8o
Veteran Member
m8o's Avatar

Join Date: Jul 2007
Location: 40°-55'-44" N / 73°-24'-07" W [on LI]
Photos: Gallery | Albums
Posts: 3,092
QuoteOriginally posted by OniFactor Quote
uhm.. one slight issue with this. ~50mm is the human eye PERSPECTIVE, not it's FOV. think of it this way. focus on the center of the monitor and see if you can see your elbows, without changing your focus. i don't think this would be possible with a 50mm FOV.
It occurred to me my point was probably not properly conveyed. I clarified that this is what I meant too, in another post [#28]. I'm 100% with you.

actually then, sorry amateur6... I got carried away and didn't realize that aspect of the eye question was OT. no prob I'm sure, but silly me for not realizing what the exact points were you specifically asked about.

Last edited by m8o; 02-26-2008 at 07:56 AM.
02-26-2008, 08:14 AM   #42
Senior Member
amateur6's Avatar

Join Date: Mar 2007
Location: Rhode Island
Photos: Gallery
Posts: 177
Original Poster
QuoteOriginally posted by m8o Quote
It occurred to me my point was probably not properly conveyed. I clarified that this is what I meant too, in another post [#28]. I'm 100% with you.

actually then, sorry amateur6... I got carried away and didn't realize that aspect of the eye question was OT. no prob I'm sure, but silly me for not realizing what the exact points were you specifically asked about.
No worries; OT is fine with me, just wanted to be clear.
02-26-2008, 12:06 PM   #43
Veteran Member
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,871
Because the "what is the eye's focal length" issue continues to be discussed...

It is 17mm Focal Length of a Human Eye , the FoV is 120 degrees per eye (180 degrees both eyes), the majority of "pixels" are in the center though, meaning the eye has a "weighted" view with a much narrower "effective" FoV in the center.

Also, the eyes' "sensor" is ball-surface shaped and not flat.

Photographers have developped the habit to summarize all this into one corresponding "normal" FoV of 40 degrees.

With 35mm film, a lens with 50mm focus renders a FoV of 39.6 degrees, why 50mm is considered to be the normal focus and why viewfinders are made to render at 100% magnification with such a lens.

Of course, those 50mm have nothing to do with the eye's focal length.

Last edited by falconeye; 02-26-2008 at 12:13 PM. Reason: added source for eye's focal length
02-28-2008, 04:45 PM   #44
Veteran Member




Join Date: Feb 2008
Location: Chicagoland
Posts: 337
Hmm looking at the info out the human eye is closest to a f/3.5 lens (typical)

Experience with seeing motion would say that the normal limit for exposure time would be 1/60-1/90 of a second. Lets say 1/80. I know I can see upto about 1/80th of a second personally. 72hz I can see a flash, 80hz I generally can't

quick experiment at f3.5 1/80 iso 1600 showed me that I needed to add about 1 2/3 stops to get to the approximate brightness I perceived.

That makes iso 5312 about the sensitivity of my eye. (Although I have large pupils and this might be reduced somewhat)
10-22-2009, 10:41 PM - 1 Like   #45
Ash
Loyal Site Supporter
Loyal Site Supporter
Ash's Avatar

Join Date: Mar 2007
Location: Toowoomba, Queensland
Photos: Gallery | Albums
Posts: 23,920
I'm digging out this old thread out of interest as I came across this article:
Clarkvision Photography - Resolution of the Human Eye

Basically estimating the conservative resolution of the eye is 576Mp given a 120 deg FOV (but we know the majority of the resolution is focused on the fovea, which has a much smaller effective FOV).

And our ISO range is from 1-800 (that surprised me).

And our DR is in the order of 10,000:1 to over 1,000,000:1!

Then our object focal length of the eye = 16.7 mm and image focal length of the eye = 22.3 mm

And apparently our eye lens has a max. aperture of f/3.5...
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
eye
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Dynamic Range on the K-x Shahmatt Pentax DSLR Discussion 33 04-22-2010 03:51 PM
Closest to the human eye? NecroticSoldier Troubleshooting and Beginner Help 24 03-29-2010 02:22 AM
Comparing the Human Eye to the Camera mithrandir General Talk 9 01-22-2009 03:37 AM
Dynamic Range Vlad Photographic Technique 5 06-01-2008 10:40 PM
effects of changing ISO on dynamic range? Gooshin Photographic Technique 8 02-08-2008 07:29 PM



All times are GMT -7. The time now is 03:55 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top