Zoom link for tonight's Solarchat 18:00UTC 29 Nov

[Montana]

Alexandra Hart is inviting you to a scheduled Zoom meeting.
Join Zoom Meeting
https://zoom.us/j/93882385058
Meeting ID: 938 8238 5058
Passcode: 905955

[rsfoto]

Hi,

Great meeting and nice to see some faces too again

[DeepSolar64]

I came on a little late but it was nice seeing all of you again. Thanks for hosting a nice meeting Alexandra. I have so much to learn.

[Montana]

As promised, I saved this explanation of adaptive sharpening in ImPPG. It is complicated and I hope that Freddie doesn't mind me posting his explanation:

Adaptive sharpening in ImPPG by Freddie
There have been a couple of questions about tone curve/histo and adaptive in ImPPG so I will try and help and build on what Michael has said.

Adaptive: This basically allows you to control the amount of sharpening applied to dark (low signal) and bright (high signal) parts of the image. This is because if you apply the same amount of sharpening across an image, the sharpening will be fine in the bright parts but will introduce noise to the darker parts or will be fine in the darker parts but the brighter parts would take more sharpening. ImPPG controls this by allowing you to adjust “amount min” the amount of sharpening in the dark parts and “amount max” the amount of sharpening in the bright parts. The thing that defines what is dark and what is bright is “threshold” so adjusting “threshold” will change the brightness level where the transition from amount min and max occurs. The “transition” setting basically allows you to set a band of brightness over which the change from amount min and max occur so it isn’t a sudden change.

The best way to get into this is probably fire up an image, apply a lot of sharpening and set amount max really high ~15 (a lot of sharpening) and min to say 0.6 (a bit of blurring) Now just look at the dark sky background of the image and adjust the “threshold” and keep looking at the dark part of the image, as you adjust it you will see the background become noisier as sharpening is applied to the dark region, now just adjust the other way and eventually you will see the background go nice and noise free as the background changes from being sharpened to blurred. Adaptive!!!! Interestingly the person in the video has this exact problem as he didn’t like the sharpening as he said it added to much noise to a dark part by the prom so he dialled back the sharpening a touch. He made no mention of adaptive and didn’t have it set so I guess he wasn’t aware of how to use it.

Tone curve/histo: Best thing to do is ignore moving points up, down, left or right and just think about what the point/curve actually means. An unchanged image will show pure black on the left and pure white on the right and all shades of grey in between. The tone curve is the line between all these points. The brightness of any point on the curve can be adjusted by moving the curve from its original diagonal position. Obviously pure black can’t be made any darker so the far left can’t be lowered and pure white can’t be brightened so can’t be raised. Any point in between can however be adjusted. Again best way to do this is by looking at an image. Look at the dark background, put a point on the left part of the curve, move it up and the dark part gets brighter but notice, it’s not just the very dark point you picked that has got brighter the dark grey parts of the image have also become brighter. Look at the curve though and you will see that the by dragging up a single point has created a nice curve in what was once a straight line so any parts that are above where they were on that original line will have also become brighter, not just the point you dragged up.

Now look at why you sometime get some odd things happening when you have a couple of points selected on the curve. Fire up an image again and start with an unchanged tone curve i.e. a nice diagonal line. Just put a point in the middle of the curve don’t change the shape of the curve, leave it as a straight diagonal line. Now go to the left side of the curve and as you did before, drag a point up to brighten the dark parts of the image. The dark parts brighten but strange things also happen to the lighter parts. Look at the curve, the point you put in half way along has acted like a pivot and the curve to the right of it has now gone down and we know from before that as the curve there is now below it’s starting position those points have now become darker. This is why you need to be careful when you have multiple points on a curve as an adjustment to one point on a curve can have unexpected consequences to another part of the curve unless you keep an eye on how that curve is changing. If a part of the curve has moved that you didn’t want, just drag it back into place or put a point on the curve which will prevent that particular point from moving.

Hope all of that is of some help.

[p_zetner]

Thanks for hosting the meeting, Alexandra.
Sorry I had to duck out earlier than anticipated but I enjoyed seeing the group.
Cheers.
Peter

[MapleRidge]

Great to see everyone earlier today and a big thanks to Alexandra for hosting

It was good to catch some fine points on the software that was reviews too...we call can learn

Brian

[ffellah]

Thank you all who attended the Zoom meeting today. It was great spending some time together during these COVID times with friends that share the same passion for solar imaging. Thank you Alexandra and Brian for setting this up.

Franco

[pedro]

I missed this zoom meeting...

[DavidP]

Sorry I missed this. Are these meetings on a schedule?

[DeepSolar64]

Great to see everyone earlier today and a big thanks to Alexandra for hosting

It was good to catch some fine points on the software that was reviews too...we call can learn

Brian

Brian, you showed some awesome loop limb prominences on during the meeting. I think they were from today. I hope you post them. They looked really good.

James

[DeepSolar64]

I missed this zoom meeting...

I missed seeing you there. You had a lot to add to the last one with all of your awesome experience.

James

[MapleRidge]

Thanks James!!!

I will get them posted in the next day or so..still processing them and will have to grab some sleep and work tomorrow too

Brian

[DeepSolar64]

Brian,
I know what that's like! There's always work.

JP

[Montana]

Thanks everyone for turning up

We could make a schedule if you like? Maybe the last Sunday of every month at 18:00 UTC??
However this does favour Europe and North/South America, maybe an Asia/Australia might want one as well but that depends on who is interested.

Maybe we could also schedule an informal discussion for meeting too. It was great to see Rainer's image processing workflow compared to mine. Maybe each meeting someone could volunteer to either educate us on something interesting they found out about the Sun or show us their workflow so we could discuss it? It is all about learning and making friends

I am up for suggestions, if it is popular then we can can do this. Please let me know what you think even if it is positive or negative.

Alexandra

[pedro]

Didi you record the zoom meeting Alexandra?

[Montana]

No sorry Pedro I didn't. If I did I don't have a Youtube account to post it. I presume anyone could record it if they wanted to or does the host have to do it?

I guess we would need to ask folk if they minded their conversations being recorded.

Alexandra

[pedro]

Ok, no problem. I will join you in future zoom meetings

best regards

[Lowjiber]

I too missed the Zoom meeting. A tentative schedule would be nice. I'm retired, so any time is convenient for me.

John

[rsfoto]

Thanks everyone for turning up

We could make a schedule if you like? Maybe the last Sunday of every month at 18:00 UTC??
However this does favour Europe and North/South America, maybe an Asia/Australia might want one as well but that depends on who is interested.

Maybe we could also schedule an informal discussion for meeting too. It was great to see Rainer's image processing workflow compared to mine. Maybe each meeting someone could volunteer to either educate us on something interesting they found out about the Sun or show us their workflow so we could discuss it? It is all about learning and making friends

I am up for suggestions, if it is popular then we can can do this. Please let me know what you think even if it is positive or negative.

Alexandra

Hi,

Any day is OK. I downloaded a timetable covering the three parts of the world.

My Place is Central time in America -6 UTC, London is UTC +-0 and Canberra, Australia UTC +11 would be the other side of the World.

As you can see the poor other side of the World and even worse Down Under would need to make the meeting during Breakfast (next day), UK at Supper and America during Lunch.

Meeting_Timetable.JPG (245.74 KiB) Viewed 585 times

[rsfoto]

No sorry Pedro I didn't. If I did I don't have a Youtube account to post it. I presume anyone could record it if they wanted to or does the host have to do it?

I guess we would need to ask folk if they minded their conversations being recorded.

Alexandra

Hi Alexandra,

Yes. Next time I will try to record it but it would be good for redundancy purposes that 2 or 3 more also do it.