The Joy of Pixel Density

Started Jul 13, 2008 | Discussions thread
OP John Sheehy Forum Pro • Posts: 21,722
Re: The Joy of Pixel Density

ZorSy wrote:


I re-read this post several times and I am intrigued with what you
are saying - sorry if I am slow to understand (it's not the language
but method) so please correct me if I am wrong here:

you are comparing pixel density per surface units, right? SO for your
test you actually used as much surface from 400D sensor as much is
the FZ50 CCD surface, resulting in fewer total pixel count from 400D,
for which reason you had to uprez fewer pixels from that sample to
match the total number of "true" pixels full FZ sensor provided?


my understanding of presented, you are comparing the uprezzed crop
(which is now 100%) to a 100% crop from FZ (and then the whole lot
being pushed up)?


If my understanding is not right, could you please explain again your
workflow for this test. In your OP you said the shooting parameters
were the same including the focal lenght, I guess equaling it
xx/35mm. Yet this is where the term "area" comes in place before the
pixel count.

The actual focal length at the "420mm" (EFL) end of the FZ50 is 88.5mm. The lens on the 400D was 22mm, So, I dialed in about 105mm (EFL) on the FZ50, to approximate the same real focal length. My estimation in dialing was pretty good, because when I used the 5.7:1.97 (2.89:1) ratio for scaling crops up and down, the subjects were almost exactly the same size on screen.

I did something similar comparing two different cameras (D80 and
Fuji 9500, the second using SCCD resulting in 18MP interpolated
JPEG), but my findings are somewhat quite opposite to yours, even
using base ISO 80 on Fuji.

May be something you did, may be the converters; it's hard to tell from a vague description of what you compared.

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