You might find it very instructive to read this article
<http://www.luminous-landscape.com/tutorials/resolution.shtml>
But it's quite long and technical. If it gets too tedious you might
just decide to cut to the chase and refer to table 3 about 80% of the
way down the page.
To save you some work in trying to decipher the table the table shows
four major columns representing different sensor formats from 4/3 to
medium format. Within each of those major groupings are 3 sub-columns
that represent a wavelength of light... 0.4 microns (blue), 0.55 microns
(yellow-green, the max sensitivity of the human eye) and 0.7 microns
(red). For simplicity the attention is focused on the 0.55 micron
yellow-green. At far left you see focal ratios listed. The contents of
each cell in the matrix represent the maximum *theoretical* number of
pixels that can be resolved at a given wavelength within a given sensor
size.
The example given in the text concentrates on f/11 and shows the
resolution values for yellow-green underlined in the table. For a four
thirds sensor (eg: E-1, E-3) the maximum resolution at f/11 is 4
megapixels. For an APS-C size sensor (Canon, Nikon, Sony, Pentax, etc,
small sensor cameras) the max is 7 megapixels. For a full-frame 35mm
size sensor the max is 16 megapixels. If you consider the blue
(shorter) wavelength you'll see the resolution is higher. And the red
(longer) wavelength has even less resolution.
You must also keep in mind that these numbers are maximum theoretical
values and don't consider the vagaries of imperfect lenses or
interfering anti-alias filters. They are why I try to keep my Canon 5D
shots at f/11 or larger apertures whenever possible. You should also
note that, at f/16, on either the the E-1, E-3 or any 4/3 camera that
the maximum resolution for yellow-green is only 2 megapixels. In
essence, if you really like the E-1 and are shooting at about f/9 or
smaller you might as well choose the E-1 over the E-3. Diffraction at
apertures smaller than f/9 will limit the resolution to the 5 megapixels
attainable on the E-1. The higher resolution of the E-3's sensor will
not be attained no matter what you do. And for those f/16 shots it's
likely that you maximum resolution is something less than those 2
megapixels. At best you're probably making images good enough for an A6
size print but not appreciably larger.
But the best way to make sense of all this (including your specific
lenses and anti-alias filters) is to shoot some test images. I would
suggest using real-world objects for the test but those with little
depth such that depth of field is not a significant confusion factor.
Shooting at f/5.6 should allow attaining maximum sensor limited
resolution on either the E-1 or E-3. Even at 54mm, if shooting at f/5.6
at a distance of 2 meters the depth of field is still close to 25mm
assuming a page size print. If shooting at 25mm focal length at 2
meters distance at f/5.6 the depth of field extends from approximately
1.5 to 2.8 meters. Such would allow using something like a pot of
flowers as a test case. Depth of field would be more than adequate at
f/5.6 and any degradation at smaller apertures would be due (mostly) to
diffraction.
Chuck Norcutt
On 5/8/2011 8:43 AM, Brian Swale wrote:
> Chuck wrote
>> I can't argue with the results but keep in mind that you are playing a
>> trade-off game of depth of field against resolution loss due to
>> diffraction. The E-1 is diffraction limited at about f/9, higher res
>> E-thingies at about f/6.3.
> And Ken wrote
>> Chuck, I beg to differ on the E-1's diffraction limits. The limit is
>> not a brick wall,but a gradual loss of resolution. The E-1's AA filter is
>> so blasted overspec that diffraction limitation is more of a philosphical
>> debate than something that is ever seen--especially when you consider that
>> we have good sharpening tools to fix much of it, anyway. But I do see
>> evidence of it around the point you say, but it's almost always a
>> non-issue.
>
> I have been taking "landscape" photos at f/16 with the E-3 and Zuiko 14-54,
> IS off and on a tripod. I an not happy about how sharp the results are.
> Same applies to some recent close-up shots with this lens - the one that this
> camera was fine-tuned for a few months ago at some expense to get more
> accurate close focussing.
> I've been doing some backup shots with the OM4T, but since I'm hundreds
> of Kms from a processor it will be weeks before I see the results of film.
>
> Is it likely that at f/16 on digital the image degradation will be easily
> observable ? I think I see it when I look at the pixies using FastStone Image
> viewer.
>
> Can you say more about anti-aliassing, not only re the E-1, but also re the E-
> 3 since that's the one I use mostly these days?
>
> And as a comment on another topic, I think that sometimes I *do* get
> shutter lag; but least with the E-1. I used the E-1 at a childrens party
> recently
> and was delighted to rediscover how quiet the shutter system is and how
> responsive the shutter release is.
>
> Thanks
>
> Brian Swale.
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