Archived posting to the Leica Users Group, 2009/11/19

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Subject: [Leica] Thought question re antialiasing
From: dstella1 at ameritech.net (Dante Stella)
Date: Fri, 20 Nov 2009 01:09:50 -0500
References: <494971.52240.qm@web83908.mail.sp1.yahoo.com> <20091120032721.GA2535@d242.scdc1.swarthmore.edu> <4796FFE1-49FB-45D9-8E75-A381DCB355E3@ameritech.net> <20091120035749.GB2535@d242.scdc1.swarthmore.edu> <36172e5a0911192044s197d811ao879d833085c1a661@mail.gmail.com>

Kodak is a little bit cagey with the info on the offset lenses on the 
KAF-10500 and its bigger brother.  I think the microlenses are tailored to 
the application.

What got me thinking about this is that I have an M8 and a Kodak 14n.  
Neither has an AA filter, but the 14n also lacks microlenses.  If you 
process RAW files for both through Lightroom (so you don't get contamination 
from any in-camera correction), the 14n will produce insoluble moire much 
more of the time - sometimes to the point where inducing diffraction by 
stopping down the lens to f/11 is the solution.  On the other hand, the 
Leica virtually never hits this point.  But given the tighter pixel pitch 
and even higher-resolution lenses, one would expect it to.

My hypothesis (which might be wrong) is that the little lenses (completely 
offset or not) are acting as something of an AA filter - and what we all 
take to be sharper pictures from no AA filter is really higher-contrast 
pictures from higher-contrast lenses.  Both the M8's and M9's resolutions 
are 73lp/mm (at least according to Reichmann), and it should be routine to 
cross that at wide apertures with M lenses.  But the incidence of moire at 
any aperture is so low as to suggest that the barrier rarely gets crossed.  
That suggests something acting as a limiting factor on resolution.

Something interesting, BTW, is the difference with and without AA filters.  
If it is a relatively weak filter, as on the Nikon D3, removing the AA 
filter actually does very little.  Go here:

http://bythom.com/nikond3xreview.htm

And take a look at the with/without pairs for the D3 and D3x.  Very 
interesting.

Dante



On Nov 19, 2009, at 11:44 PM, Geoff Hopkinson wrote:

> My assumption also. Perhaps there is info on this available from Kodak, or
> Dante has it already? Interesting technically anyway.
> 
> 2009/11/20 Tim Gray <tgray at 125px.com>
> 
>> On Thu 19, Nov'09 at 10:37 PM -0500, Dante Stella wrote:
>> 
>>> They do span more than one pixel - that's why they're called offset.  And
>>> that is why I asked.
>>> 
>> 
>> Ahh, I wasn't aware that they did that.  I interpreted the offset
>> microlenses as not being centered directly over a pixel, but still 
>> funneling
>> in light into just one pixel.  Thus, enabling light to come in at more
>> oblique angles and still be captured.  I drew an ascii diagram, but I'm 
>> sure
>> most everyone's mail client will mangle it, unless you have monospaced
>> fonts.
>> 
>> -------
>> \     |
>> \    | <- offset lens
>> \___|
>>  |  | <- pixel
>>  ----
>>  As opposed to
>> 
>> -------
>> \     /  <- non-offset lens
>> \___/
>> |  |  <- pixel
>> ----
>> 
>> 
>> _______________________________________________
>> Leica Users Group.
>> See http://leica-users.org/mailman/listinfo/lug for more information
>> 
> 
> 
> 
> -- 
> Cheers
> Geoff
> http://www.pbase.com/hoppyman
> 
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information



Replies: Reply from hopsternew at gmail.com (Geoff Hopkinson) ([Leica] Thought question re antialiasing)
Reply from grduprey at mchsi.com (grduprey at mchsi.com) ([Leica] Thought question re antialiasing)
Reply from tgray at 125px.com (Tim Gray) ([Leica] Thought question re antialiasing)
In reply to: Message from dstella1 at ameritech.net (Dante Stella) ([Leica] Thought question re antialiasing)
Message from tgray at 125px.com (Tim Gray) ([Leica] Thought question re antialiasing)
Message from dstella1 at ameritech.net (Dante Stella) ([Leica] Thought question re antialiasing)
Message from tgray at 125px.com (Tim Gray) ([Leica] Thought question re antialiasing)
Message from hopsternew at gmail.com (Geoff Hopkinson) ([Leica] Thought question re antialiasing)