Shooting Flats

[Guest]

I've been shooting flats by aiming my camera at white cloud. It doesn't usually help much. I've discovered the value of shooting darks during the same session I'm snapping light frames.

 

I'm thinking of making a "Pugh Mask". The idea is to place a white sheet of paper over the objective and shine a torch at an oblique angle. I'm thinking of using cardboard holders, in the same way I do for solar filters.

 

Think it will work?

[Perkil8r]

No, it will need even illumination so lighting at an angle will induce a gradient. Best thing is a white t shirt over the end and point up at the sky during daylight.

[Guest]

Thanks, Mike.  What I want to do is take the flats in the same session that I'm taking the lights and darks.

[+Graham]

I found the best thing to use is a clean blank laptop screen.

Just get your laptop to display a white screen then adjust the exposure time until the histogram reads about 2/3 of the scale.

[Perkil8r]

What Graham said then

[Werisit]

hi Phil. Your darks need to be taken at the same temp (ambient and sensor) as your picture files. Best to cap the lens at the end of a session and do it there and then. I just leave it going on the intervalometer while I pack away all the other gear.

 

[glider]

I do what Graham said, using the laptop screen.

 

You need to do the darks at the same temperature so best done on the night. The flats you can do anytime, just don't let the imaging train move. I've done them days later.

 

You can build a flats library at different temperatures and durations. I used an environmental chamber at work and did them at 5 degC steps. Then use the set that is closest to the temperature during the imaging run.

 

 

 

[Guest]

I've had better results when shooting darks at the same time and also since I've started using at least 8 darks.

 

I'll try the laptop screen trick.