• Please use real names.

    Greetings to all who have registered to OPF and those guests taking a look around. Please use real names. Registrations with fictitious names will not be processed. REAL NAMES ONLY will be processed

    Firstname Lastname

    Register

    We are a courteous and supportive community. No need to hide behind an alia. If you have a genuine need for privacy/secrecy then let me know!
  • Welcome to the new site. Here's a thread about the update where you can post your feedback, ask questions or spot those nasty bugs!

using IRIS and unkown raws?

T

Torsten Kötting

New member
hi there,

a friend was kind enough to provide me with 3 blackframes from the 5dmk2. Since IRIS doesnt know that cam (trying to load one doesnt really work ... surprising since it should be the same as the 1dsm3 files?) im trying to figure how to work with dcraw. From what i've read so far i use dcraw with the options -4 -D and then pnmtofits in_filename > out_filename. When doing so and loading the resulting fits-images into IRIS i get the following values with 'stats':

iso100: Sigma 6.2
iso1600: Sigma 10.4
iso6400: Sigma 41.5

but i dont know if theres values are correct ... if someone wants the raws:

http://www.pipetrap.de/stuff/5dmk2/

(and the friends websites, really nice Astro-Images: http://www.kopfgeist.com)
 
J

John Sheehy

New member
Torsten Kötting said:
hi there,

a friend was kind enough to provide me with 3 blackframes from the 5dmk2. Since IRIS doesnt know that cam (trying to load one doesnt really work ... surprising since it should be the same as the 1dsm3 files?) im trying to figure how to work with dcraw. From what i've read so far i use dcraw with the options -4 -D and then pnmtofits in_filename > out_filename. When doing so and loading the resulting fits-images into IRIS i get the following values with 'stats':

iso100: Sigma 6.2
iso1600: Sigma 10.4
iso6400: Sigma 41.5

but i dont know if theres values are correct ...
Click to expand...

They load into IRIS, but only a 1/4 height of the image loads, rotated. The values I get in IRIS loading the 1/4 image are the same that you get going through DCRAW. I binned the data, and it appears to be unfiltered; the read noise really is that low at high ISO. The question is, where are the true ISO greypoints in these images? That determines the real noise sensitivity.

It seems odd that ISO 100 read noise is so close to 1600. When you look closely at the ISO 100 blackframe, it has a lot of banding. I wonder if this is specific to this camera, or general for the 5D2. If it is general, then the 5D2 is going to be inferior to the 1Ds3 at ISO 100, even if better at high ISO.
 
T

Torsten Kötting

New member
John Sheehy said:
They load into IRIS, but only a 1/4 height of the image loads, rotated. The values I get in IRIS loading the 1/4 image are the same that you get going through DCRAW. I binned the data, and it appears to be unfiltered; the read noise really is that low at high ISO. The question is, where are the true ISO greypoints in these images? That determines the real noise sensitivity.

It seems odd that ISO 100 read noise is so close to 1600. When you look closely at the ISO 100 blackframe, it has a lot of banding. I wonder if this is specific to this camera, or general for the 5D2. If it is general, then the 5D2 is going to be inferior to the 1Ds3 at ISO 100, even if better at high ISO.
Click to expand...

hmm, but do these sigma-values represent 16-bit? during conversion the raw was transformed into 16bit files .. but the values are too good for 16bit me thinks ...
 
J

John Sheehy

New member
Torsten Kötting said:
hmm, but do these sigma-values represent 16-bit? during conversion the raw was transformed into 16bit files .. but the values are too good for 16bit me thinks ...
Click to expand...

DCRAW uses whatever bits the original RAW has as Least Significant Bits in its 16-bit output; a really bad idea, IMO. This means that the data gets quantized as soon as it goes into programs like photoshop.
 
B

Bart_van_der_Wolf

pro member
Torsten Kötting said:
imaging-resource has lots of raws to download now ... too bad they are done with an extender ...
Click to expand...

Hi Torsten,

It's not an extender, but the target was shot at 2x the distance (or half the size), so the numbers should be multiplied by 2.

They also have some regular full frame shots (with a Sigma 70mm macro lens) of the target.

Bart
 
You must log in or register to reply here.
Top