New Tool: HDRComposition

vicent_peris

PTeam Member
Sep 3, 2004
995
12
Valencia (Spain)
www.astrofoto.es
astropixel said:
The speed is phenomenal. Two questions though. What are optimal settings for terrestrial shots? Should I first calibrate daylight images?

This is the result of HDRcomposition of RAW images.
Hi,

This algorithm is designed to work with calibrated data. In daylight, as exposure times are very short, you don't need to subtract thermal noise. Also, if all the HDR exposure set is done with the same aperture value, you don't need to correct vignetting. But you must always correct all the image set by subtracting bias.

Just a note: to me it seems that you're making the HDR composite image with bayer matrix images. You must debayer all the images before making the HDR composition.


Best regards,
Vicent.
 
A

astropixel

Guest
Thanks Carlos and Vicent.
I'll have to take some bias frames for this particular camera.
Debayering was the solution. A bit too much colour saturation may be?
 

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astropixel

Guest
Not to the previous image. This one has HDRWT 2 layers 5x5 Gausian to luminance with deringing, plus a saturation and RGBK curve and additional colour saturation.
 

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vicent_peris

PTeam Member
Sep 3, 2004
995
12
Valencia (Spain)
www.astrofoto.es
Hi,

better would be to use more layers. With only two layers you are having too much contrast in the sea, over the reflected Sun light.

OTOH, after HDRWT is better to use curves to enhance colors, because HDRWT mutes the color saturation of the highlight areas. Do a curve to saturate only the color of the less saturated pixels.


Regards,
Vicent.
 
A

astropixel

Guest
Thanks Vicent. I think this one is a lot better. I'm almost tempted to write up a small tutorial for the procedure.

I've created and calibrated the images with a master bias, debayered, HDRComposition, SCNR green channel, HDRWT 6 layers 5x5 gaussian to luminance with a mask and deringing, a bit of saturation with CurveTransformation in H, b and RGBK, and that's it.

The only point, is that the colours could be saturated more or the contrast increased I suppose. Depending on personal preference.



 

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Alejandro Tombolini

PixInsight Ambassador
Juan Conejero said:
The resulting HDR image is extremely dark, as expected. It is a linear image with a huge dynamic range (the whole range of the M42/M43 region) stored in a numeric range of at least 230 discrete sample values. Note that this HDR image does not fit into a 32-bit floating point image, where you can store a maximum of about 224 discrete values. This HDR image requires either the 32-bit unsigned integer format or the 64-bit floating point format, both available in PixInsight. The HDRComposition tool generates 64-bit floating point images by default, although 32-bit floating point can also be used as an option suitable for moderately large HDR compositions.


Here is the HDR image with an automatic STF applied. STFs are 16-bit look-up tables in PixInsight. Note that a 16-bit LUT causes posterization in the screen representation of this image. There is no surprise here, since as noted this is a 64-bit floating point image storing more than 230 discrete values.

My image is even with more posterization. Is there any way to visualize correctly and apply 
deconvolution without use histogram and lose linearity..., I can not see it good enough, mainly in dark regions.

Alejandro.