114 replies to this topic

[Tom and Beth]

Ahhh, another mountain to climb. Thanks, esp David Ault for your writeup.

 

As you can see, I need a BUNCH of help on this aspect

 

I did crack the door on 30 minute subs, though.

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[Jon Rista]

The big thing with metallic is the way it enhances depth. It's usually described as "3D"...I think that is an inaccurate term. It really brings life and a sense of depth to an image, but they don't actually look "3D", not in the sense of say a 3D movie or something like that. You will probably lose a bit of resolution with metallic, just because of the issues with how they reflect light. Metallic is pretty unique...I'd say it has it's own role outside of any kind of scale you might put to other papers. Matte papers can actually reveal incredible resolution...I print on a number of fine art natural fiber papers, like Hahnemuhle's Photo Rag, to get the maximum resolution out of my prints with the fewest reflectivity issues. Canvas, again, can support high resolution, but texture is an added factor and it can affect how people perceive that resolution. Glossy is more for the dynamic range and/or contrast, but again, it's not so cut and dry. Moab's Lasal Photo Matte has both superior resolution and superior dynamic range, but it's a matte w/ OBA. 

 

Metallic's are usually glossy or semi-glossy, some types can support very high resolution, but the key with a metallic is the way it makes your images look. How and where it brings parts of your image to life, gives them a sense of "thereness"....the life and depth, the way the details change as you move towards the print, etc. Not all metallics are good. I've seen some that are ok, some that are great, and some that are just mindblowing. I met a guy at a local frame shop once who had a 24x16" print on a super thin copper metallic base. It was one of the most amazing metallic prints I've ever seen. It wasn't pure copper, it was some kind of alloy to give it a more neutral "white" color...but the way the print reflected light was amazing. Metal prints are all about the effect. Sadly, you need to see it to understand what that effect is, because it's a visceral thing. 

[mostlyemptyspace]

Hmm.. Well hey, you've piqued my interest. I'm gonna give metallic a shot. Worst case, I have a print I don't super love and I don't buy that kind again. Now I'm still concerned with exposure and color balance, so I'm going to call the print shop tomorrow and see what they have to say.

[Jon Rista]

You can always buy the smallest size and see how it looks. That saves a lot of money. Hold it up to the wall where you think you want the print, or use double-sided tape on the back (don't tape the front) and stick it to the wall, and see how it looks from different angles. Metallic prints can be amazing, but they do need to be properly illuminated. You'll understand once it's in hand. 

[David Ault]

That's a lot of good information there Jon!

 

Tom and Beth, that's a fantastic image of NGC2371!  You even got a lot of the detailed structure.

 

Regards,

David

[entilza]

David thank you for this great workflow.  I tried your steps and was having success until i got to one step near the end:

 

"By the way, if you do a STF on your image now it will look horrible.  This is because the background noise has been compressed so STF thinks it can stretch the image a lot more.

Next we are going to stretch the image.  Clear any STF stretch on the window and bring up the HistogramTransformation tool.  I’ve used the MaskedStretch process in the past but in the case I felt it flattened the image too much but feel free to give it a try.  You can click on the preview icon to see instantaneous results of your stretching.  Play with the settings in the HT tool and then apply it to your main image.  I used the settings in Figure 24 and ended up with the image in Figure 25."

 

The image was starting to shape, however I did the STF and yes it did overstretch and I couldn't alter out the HistogramTransformation tool back to what it was before this step.

 

Could you clarify this on how to manipulate the histogramtransformation so precisely?  previously I was just using STF and draging the process to HistogramTransfer and continuing on but I don't think you meant for that here..

 

Thanks!

[David Ault]

etilza,

 

Good question.  Let me see if I can answer your question be describing the STF and HistrogramTransformation tools in a bit more detail.

 

Here's the STF with some key items labeled:

 

- The 'Color Channel Link' button locks the channels so that when an adjustment is made it is mirrored in the other channels.  When unlocked you have separate access to red, green & blue sliders.

- 'Auto Stretch' does exactly what it says.  It clips the shadows by a set amount and then stretches the midpoint until it is at 25% of the histogram.

- 'Track Active View' is on be default so that as you switch image windows STF is now working on that image.  You can have separate STF settings for each image window.

- 'Reset' restores all the settings to their defaults.  So in the section in question where I say, "Clear any STF stretch on the window," this is what I'm referring to.

 

Next the HistogramTransformation tool.  There's a lot going on with the HT tool and I've highlighted just a few of the items here:

 

- The top and bottom displays in HT are the output and input histograms, respectively.  You make adjustments in the lower display and see the effects in the upper.

- 'Manual Adjustments' are exactly that.  Click and drag on any of the 3 markers to alter the shadow clipping, midtone and highlight clipping points.

- 'View Selection' allows you to select a specific view to see what your histogram looks like for that image and what any transformation will do to that data.

- 'Channel Mode' alters which color channel you are working on.  You can make different changes to R, G, B, RGB/K and alpha to do very complex adjustments in one pass.  I tend to alter one thing at a time.

- 'Manual Numeric Adjustments' are the same as the 'Manual Adjustments' except you can entire the numeric value directly.  These range from 0.0 to 1.0 instead of ADU values.

- 'Zoom Levels' allow you to inspect a specific portion of the histogram or alter the shadow, midtone or highlight points with more accuracy.  You can also use the mouse wheel when hovering over either histogram display.

- 'Clipping Options' allow you to auto clip to specific values.  The left most icon does't technically clip anything.  Instead it adjusts the shadow or highlight clipping point to the minimum or maximum value in the image.  So if the minimum value in my image was 0.0523 when I click on the 'auto zero shadows' button you'll see the shadow level change to 0.0523 and 0 pixels clipped.  The middle button clips to a percentage of total pixels defined in the 'Auto Clip Setup' section.  The right button resets the clipping.  These buttons are mirrored for the highlights on the row below.

- 'Track Active Window' will display the histograms and associated output transformed data for the active window.  If you switch windows, you'll see the histogram information change as well.

- 'Reset' resets all settings to their defaults.

 

If you like the way STF auto stretches your data you can make it permanent by dragging the 'new instance' icon (the little triangle in the lower left) of the STF window to the bottom bar of the HT window.  You'll see the 'Manual Adjustments' change as well as the output display.  If your window is active you can hit the square 'Apply' icon in the lower left of the HT window to apply those settings to your image, or you can drag the 'new instance' icon to your image.  Either method works.

 

Sometimes you may want to use the STF auto stretch as a starting point.  You do the same as above, except this time make whatever adjustments you deem necessary and then apply the HT to your image.

 

A couple important points:

- The little open circle in the lower left of the HT window is the preview function.  If you click this it will open a reduced version of your active window that will instantaneously respond to the adjustments you are making.

- Make sure and reset the STF before doing any HT functions to an image (if you are applying your STF auto stretch to the HT tool make sure to do that first before resetting STF) or looking at the preview.  Otherwise you are looking at an already stretched image when making your adjustments.  Since STF is non-destructive it isn't altering the data, just how it's displayed, but if it is active on an image you can't really see what your HT adjustments are doing to the raw data.

 

I'm not sure if I answered your specific question but if not, let me know and I'll try again.

 

Regards,
David

[pedxing]

Great info David!

 

A couple other pointers for using HT:

 

Transferring a STF to the HT works, but I normally don't use it that way except maybe for a final tweak (and for adjusting masks). The problem with using it from the beginning is that you end up doing your stretch all at once, and in general it's better to stretch in stages.

 

When it comes to stretching using the HT, usually you are going to drag the middle manual adjustment arrow to the left until details start to show up in the preview (but not too extremely). Then you apply and reset the HT and do a gentler stretch, watching the upper (output) histogram.  Normally you're working on getting that peak to about 30%. After 2-3 stretches, you use the left manual adjustment arrow to set the black point, being very conservative - you don't want a black background, it should be just a bit lighter than black.

 

Like David said, when working with HT, first step is to reset the STF. Use the preview (circle icon at the lower left of the window) to see a preview of what's going to happen. One of the more common mistakes is forgetting to reset the HT between stretches....

[nitegeezer]

This thread has been added to the pinned "Best Of" thread.

[mostlyemptyspace]

Awesome! Yeah this thread has been amazing. Thanks everyone!

[rflinn68]

Wow! Just scanned over this thread. This is great! I need to take some time and really read through it. Thanks out to David and everyone that contributed! 

[David Ault]

Thanks guys!  And thanks to Jon and and everyone else for their contributions.

 

I've posted this same example to my website with Mostlyemptyspace's permission if you want to reference it on one page:

http://trappedphotons.com/blog/?p=642

 

Regards,

David

[mostlyemptyspace]

So to bring this thread to a happy conclusion, I received my print today! It arrived super quickly and it looks great! The metallic print is a subtle effect, and it looks pretty much exactly like it does on screen, except maybe with a darker background. This is the start of my new astrophotography wall. I'm super happy!

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[David Ault]

That looks awesome!

 

Regards,

David

[Lord Baltimore]

I know this is an old post, but for someone like me who is absolutely new to Pixinsight it makes essential reading. Being able to get hold of the data and follow everyone's suggestions is great.

Fine, it will take several read through's and several goes at everything, but at least its a massive help.

Thank you to all involved.