D70 buffer

The D70 manual p 45 show that the buffer
holds fewer medium images (7) than large images ?
Is that correct or am I misreading ?

" schreef in bericht
ups.com...
The D70 manual p 45 show that the buffer
holds fewer medium images (7) than large images ?
Is that correct or am I misreading ?


This is correct,
For the large pictures it has only to hold the large picture and no smaller
version of that picture.
For the small pictures it has only to hold the smaller picture and throw
away the larger picture,
the smaller picture can easely be computed from the larger picture by just
using a simple algoritm,
adding the two green (bayer pixels) and getting the red and the blue pixel.

For the medium format picture the original picture in large format has to be
kept until the medium
format is 'calculated' from that. Because the medium format pixel is not an
exact mapping on the
original size, this is difficult to calculate and hence will take some time
therefore both pictures have
to be kept in the buffer at that time, this takes more space than larger
picture only.
The endresult is not taking more buffer space, but the time the bufferspace
is also needed for the
larger picture is greater, so the buffer can contail less pictures.

So the number of pictures is correct.
Using a fast CF card you can often take more pictures in a burst than the
numbers given in the manual.
(Could be that for medium pictures the processing power is the bottle neck
and not the write speed of
the card)

ben brugman

Thank you for that very clear explanation of a
puzzling set of numbers
Graham Rice

Perhaps the quality setting is applied while writing to the card.

--
Joan
http://joan.colley.name:85

"Ed Ruf (REPLY to E-MAIL IN SIG!)" wrote in message
...

While this would explain why the number is lower, it does not explain why
the number is fixed regardless of the quality setting.
--
Ed Ruf Lifetime AMA# 344007 )
See images taken with my CP-990/5700 & D70 at
http://edwardgruf.com/Digital_Photog...ral/index.html

I must agree with you that my explanation does not explain why
for the medium format does not vary.
But neither are the other numbers explained.

Buffer comming from the sensor is roughly 9 Mb in size.
When the picture is taken the buffer should have room for these
'last' 9 Mb. The other space in the buffer can be taken with
compressed or non-compressed previous picture.

Maybe the buffer needs some tempory space for the compression.
Because only 4 raws fit in the buffer. The 7 medium formats can Not
be kept in the buffer as 4 raws so some 'compression' must have been
done on the 7 but compression can not be completed because then
more should fit in the buffer.

But the same goes for all the numbers in the column, I can not totaly
explain them. But when you take the pictures the numbers are displayed
in the viewfinder as wel, so I it is very unlikely that the numbers are
wrong (typo's etc.).

But a lot of the internal working of the Nikon system is not
explained to the customer. So we have to live with that.

Friendly greetings,
Stef ten Bras


"Ed Ruf (REPLY to E-MAIL IN SIG!)" schreef in
bericht ...
On Mon, 9 Jan 2006 21:31:03 +0100, in rec.photo.digital "Ben Brugman"
wrote:


" schreef in bericht
roups.com...
The D70 manual p 45 show that the buffer
holds fewer medium images (7) than large images ?
Is that correct or am I misreading ?


This is correct,
For the large pictures it has only to hold the large picture and no
smaller
version of that picture.
For the small pictures it has only to hold the smaller picture and throw
away the larger picture,
the smaller picture can easely be computed from the larger picture by just
using a simple algoritm,
adding the two green (bayer pixels) and getting the red and the blue
pixel.

For the medium format picture the original picture in large format has to
be
kept until the medium
format is 'calculated' from that. Because the medium format pixel is not
an
exact mapping on the
original size, this is difficult to calculate and hence will take some
time
therefore both pictures have
to be kept in the buffer at that time, this takes more space than larger
picture only.
The endresult is not taking more buffer space, but the time the
bufferspace
is also needed for the
larger picture is greater, so the buffer can contail less pictures.

So the number of pictures is correct.
Using a fast CF card you can often take more pictures in a burst than the
numbers given in the manual.
(Could be that for medium pictures the processing power is the bottle neck
and not the write speed of
the card)

While this would explain why the number is lower, it does not explain why
the number is fixed regardless of the quality setting.
--
Ed Ruf Lifetime AMA# 344007 )
See images taken with my CP-990/5700 & D70 at
http://edwardgruf.com/Digital_Photog...ral/index.html