Help- Flats and Bias ISO values with banding on the flats

[pmesquita]

Hello again,

sorry for being away for a while but I try to avoid nagging you all. But this time since the question involves PI and batch pre-processing...I have to ask:

- I work with a monchromatic and TEC cooled 550d canon camera (Luis Campos MonoMod) and  Central DS RGB cooled 60d canon.
- I do Flats with Gerd's Aurora Flat panel.
- Up to very recently I was working with two TEC cooled 450d's canon cameras (Luis Campos MonoMods), one mono and one RGB.
- For over 8 months all my flats were done at ISO 1600, same as my Bias and same as my Lights.
- Now that I upgraded to the 550d Monomod and CDS canons...I've experienced Flats horizontal ligght bandings.
- I wrote to Gerd and he told me that the Aurora needs flats to be done at a speed no faster then about 1/4.

here lies my mystery: Up to now I had no problems with my flats at ISO1600 and faster speeds than 1/4. I've talked to several friends who have different theories: one says we need to do Flats at the lowest ISO possible (Gerd's Aurora panel likes than) to avoid noise on the flats, another says that the FLATS ISO HAS TO MATCH THE BIAS ISO.. This second friend says the only exception to this is if my pre-processing software (PI in my case) automatically "reads" the ISO difference between my Flats and Bias. Then it wouldn't be a problem for me to do flats at ISO100 or so (and match the Aurora panel requirements) and Bias at ISO1600.

Can someone please enlighten me so that I do the correct thing and stop having the Flats illumination banding with my new cameras? Does batch pre-processing accept Flats and Bias with different ISO's and read and compensate the difference?

thanks in advance for any help.

best regards
Paulo Mesquita

[pfile]

i think if you need to calibrate your flats with different iso bias/darks from the lights then you have to do the calibration manually. i don't believe that BPP can tell at what ISO a particular calibration or light frame was taken.

rob

[pmesquita]

Does that mean that BPP doens't work properly with different ISO Flats and Bias?

best regards
paulo

[pfile]

i believe it does not, but you'd have to read the code to be sure.

having said that maybe you can just load flats and bias and a bogus light and have it make the flat masters, then re-use those flat masters later in another instance of BPP that has the right bias and darks for the lights. (assuming the flat masters are made from calibrated subs… if not then this will not work)

rob

[Philippe B.]

Hello
I'm doing all preprocessing manualy as I use Sony A7s at 3200 iso and Flats at 400 iso
I avec made my own process icons (see on my website) but that's right some usefull addons on BPP script (in fact it should be a module and not a script) will permit to use it.
I experimented "bayer drizzle" with stand alone module (only on windows64, not on OSX because not available) but an automatic process should be nice.
Sure it will come !

[Raymond]

Hi
I had problems too in using BPP. The creation of master darks and bias and calibration made no problem, but as soon as I used a master flat (created by BPP) all the calibrated images were covered with hot pixels (light frames usually at ISO 1600 or 800; flat at ISO 200). So I made my master flat manually and the problems were gone.
Philippe, I had a look at your recent tutorial prétraitement simplifié. I'm just doing it step by step. Merci beaucoup 
Raymond

[Philippe B.]

Thank you Raymond