Exposing for proms and disk?

[kirkster501]

Hi all,

How do you balance exposure for proms and disk please?  I have acquired a Lunt 60Tha and love it.

I expose for disk at about 70% histogram and get a good disk.  But then in processing, to reveal the proms form the disk image I have to aggressively stretch because the proms are not exposed enough - even if I try and mask the disk - and the mask creates weird artefacts around the rim because pumping up the stretch causes some expansion of the disk around the edge of the mask.

IS there a way to combine an exposure for disk AND an exposure for proms and then blend them somehow?

Thank you in advance!

Steve

[Hughsie]

Hi Steve,

One option to is take an image of the disc filling the histogram to 60/70% as you have suggested and capture, say 1,000 frames.

Then increase the camera gain to say 180/200 and increase the exposure time c12 ms works for me. What you want to avoid is the disc ‘bloating’ so adjust the gain keeping the disc the same size then adjust the exposure time to bring out the detail of the proms.

Stack each file then bring both into Photoshop, copy the disc on to the prom image and set the light to difference then adjust the position of the disc so one overlays the other.

MalVeaux has some great YouTube video tutorials. This is one I sometimes work to plus he has posted an up to date one here in Solar Imaging section. It’s the first pinned subject.

 

[kirkster501]

Many thanks!  I shall look at those

 

[Kitsunegari]

what program are you capturing with; i suggest fire capture.   enabling 16bit mode will allow best capture of both prom and disc features simultaneously depending on your camera,    tutorials only go so far because everyone has different equipment.  

 

The easiest way is to just set your gamma up WHILE Capturing till you see the proms on screen with disk features.  Then adjust levels after you stack the video.

 

 

[inFINNity Deck]

Hi Steve,

 

I take another approach, shooting 30s videos using FireCapture with the histogram 85-90% filled. Then stack some 25% in AS!3 and process the output with IMPPG. Finally I just slightly sharpen the output and give it a nice orange colour:

So all is done in one single recording session: surface and proms.

Nicolàs