Maxim DL5 stacking question

[Skipper Billy]

If I let Maxim loose on my RGB subs as a group of 3 filter types then on my Lum subs - when I come to layer the RGB and the lum in PS the stars dont line up between the RGB stack and the lum layer !  (The RGB are perfectly aligned with each other its just the lum that doesnt match)

If I stack R then G then B then Lum separately and align the 3 channels in PS and layer lum on top they do line up.

Am I missing a trick ???

[opticalpath]

I presume that you are putting all your RGB images in one folder then using Process/ Stack to operate on all the files in the folder?   In that case the Stack function will align and stack the sets of R, G and B images, then present you with a combined RGB image.

If you then do the same thing separately with just a Luminance images folder, Stack will align and combine the images and present you with a summed Luminance image.  But each alignment has been done independently: all the Lums. are aligned as a set and all the RGBs are aligned as a set ...... but each set is not aligned with the other.

The easiest way to resolve this is to put all your Lum. and RGB raw images in the same folder for stacking in one step.  The stack function will then align all Lum. and RGB images together in the same process.  When the stack is complete, you will be presented with a summed RGB image as before, but also with a separate summed luminance image ..... this time lined up with the stacked RGB image.  If you transfer these images to PS they will line up.

Adrian

[Skipper Billy]

Brilliant - that all makes perfect sense now.

Thanks a million.

[opticalpath]

One other thing you might like to consider:

When you save the stacked RGB and luminance images in Maxim, choose the option to save in floating-point ('IEEE Float') FITS format initially, rather than as 16-bit FIT or TIFF.  This preserves the finer tonal range that you built up in the summed image by stacking multiple 16-bit raw images.  Then don't transfer to Photoshop straight away.  Instead perform an initial moderate stretch in Maxim (using DDP for example) and only then convert to 16 bits TIFF for transfer to Photoshop.  Doing this means that you are performing the initial stretching on a file that has a wider range of grey-scale values in the faint parts of your image, compared to saving and stretching in 16 bits which introduces some quantising error (=noise.)  Stretching in 32 bits/ floating-point introduces less noise at this crucial early stage of processing.  Having expanded the tonal range of the faint bits with this first stretch, subsequent stretching in 16 bits is much less vulnerable to noise from quantisation errors.

Adrian

[Skipper Billy]

Excellent - thank you.

I had avoided stacking all the images think it would stack the LRGB into one - I hadn't realised it was smart enough to combine the RGB but stack the L separately.

I tried it last night and it worked a charm

I will try your saving suggestion this evening.

Thanks very much for sharing your expertise.