Olympus-OM
[Top] [All Lists]

Re: [OM] clever use of available sensor real estate

Subject: Re: [OM] clever use of available sensor real estate
From: Tim Hughes <timhughes@xxxxxxxx>
Date: Tue, 5 May 2009 03:04:02 -0700 (PDT)
I read their position paper and I think some of the claims are overblown and 
maybe in some cases specious:

http://www.fujifilm.com/photokina2008/pdf/release/super_ccd_exr_e.pdf

It looks like when running in 6Mpixel modes there are some advantages in some 
ways, but not really in 12 mpixel mode.   The mode with increased dynamic range 
is an example where it maybe a fairly good tradeof,  but you land up in a mode 
pretty close to 6Mpixel rather than 12. 

For example it appears the traditional beyer pattern, which is optimised for 
highest resolution in green, since this is human eyes peak sensitivity and peak 
sunlight wavelength, will have higher horizontal resolution than the new exp 
pattern. This actually even adds a little more since the eye/brain aparently 
also subjectively percieves it to be highest reolution if it has greatest 
resolution in the horizontal direction. 

The new exp patern is quite strange in that the highest resolution in green is 
on the left diagonal , with all other directions being lower! This is 
non-optimal since horizontal is best subjectively. The beyer has equal, but 
reduced by  45% resolution on both diagonals,while the vertical and horizontal 
are the the highest and equal. 

The exr horizontal green resolution, is lower than the beyer, at 12Mpix because 
of diagonal pattern. 
Because of the unsymetrical spacing of exp, it also aliases at even lower 
resolution than you would normally imagine from that raw color pixel count. If 
you photographed a thin curved line object like a hair say, it would produce 
some additional low frequency aliasing because sampling was more non-uniform 
,at different angles than beyer. (think: if a line pair is sampled by two close 
spaced pixels then they get resolved, but the next pair of pixels in exp are 
now more widely spaced, so the next adjacent line pair is not resolved)

The wide dynamic range option which is really more like 6mpixel, since it 
selects best exposure from two diagonal pixels, then has uniform sampling, at 
least at a particular brightness level.  

The claim that there is less aliasing from binning diagonally left adjacent 
pixels in exr, rather than more widely separated ones (bayer), is complex to 
analyse and is more orientation dependent than beyer. 

However, because the beyer samples at a higher horizontal frequency than the 
non-uniform exr, then binning two horizontal (or vertical) pixels in beyer, 
still has lower aliasing, since the actual sampling was done at a higher 
resolution (frequency) thus having lowest aliasing.   

The s/n ratio improvement is exactly the same for equal area photo-diodes in 
the two technologies. In this comparison for the bayer at 6mpixels, the optimal 
bining for best subjective and actual resolution, would be combining vertical 
pixels. 

Tim Hughes




--- On Fri, 5/1/09, usher99@xxxxxxx <usher99@xxxxxxx> wrote:

> From: usher99@xxxxxxx <usher99@xxxxxxx>
> Subject: [OM] clever use of available sensor real estate
> To: olympus@xxxxxxxxxxxxxxxxx
> Date: Friday, May 1, 2009, 2:12 PM
> http://www.dpreview.com/reviews/fujifilmf200exr/page2.asp
> 
> Moose might be amused that low light performance a few 
> generations 
> later still doesn't really exceed the F30/31--the
> latter are still 
> expensive.
> 
> Not many Moose sightings of late.
> 
> A Trace Worried Mike
> -- 
> _________________________________________________________________
> Options:
> http://lists.thomasclausen.net/mailman/listinfo/olympus
> Archives:
> http://lists.thomasclausen.net/mailman/private/olympus/
> Themed Olympus Photo Exhibition: http://www.tope.nl/
-- 
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/

<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz