Tag Archives: Photoshop

Stacking: the Overloaded Word That Needs Explanation

The current rage of “stacked Milky Way” (or night sky) captures is quite different from the star trail or timestacks style of captures. Huh? The words stack and stacking are overloaded with many different meanings. Let’s see if we can add some precision and clarification.

Here are some of the variations possible:

  • Auto Blend Layers with Stacking: Used for macro/focus stacking, HDR, and generic image blending – NOT for astro images!
  • Lighten Mode Stacking: Creating Star Trails!
  • Statistics Mode Blending (Stacking): Can perform the same operation as Lighten Mode Stacking when the option “Maximum” is used, however Statistics are heavy weight and more complicated to do in our opinion.
  • Align and Stack: Deep sky astrophotography using several images taken one after another as quickly as possible. Photoshop doesn’t do this well, but we describe how in the next section. Align is the distinguishing word here.
  • Tracked Stacked Images: For still astrophotography images with less noise and greater detail. A device is required that tracks the sky rotation – the word tracked is the key here.

    Adobe Lightroom and Adobe Bridge “Stacking”

  • Group into Stack:  Not stacking at all! It really just means “create a group”.

The above is NOT an exhaustive list of the kinds of stacking you may hear about!

Stacking Types Explained

Group into Stack

Let’s start with the easy one: Stacking may mean add to group. In Lightroom and Adobe Bridge you can pick several photos and the options  Stacking -> Group into Stack. Or pick several photos and either Photo Merge to HDR or Panorama with the “Create Stack” option checked. In this context, Stacking and Stack just means group.  Unfortunately a photo can only appear in one stack, and you cannot stack photos from different folders together.

Why would you want a photo to appear in two (or more) stacks groups? Here is an example where I used a single top shot and created two different panoramas.

Panoramas 1 and 2 were both created using image 3 (608095.NEF) but when panorama 2 was created, image 3 was removed from the stack (group) for 1 and added to the stack (group) with 2. Furthermore, you can see that the panorama and the two photos used to create it were all added into the group (notice the last image says 3 of 3).

Blend Layers using Lighten Mode

Stacking may mean blend photos in lighten or darken blend mode – examples are star trails and timestacks. In this usage, the lightest (or darkest) of all the pixels in each image is selected. This is the kind of stacking that AdvancedStacker Plus does. Below is an example of taking several images that we collected over time with long delays between each exposure causing the “dotted” appearance of the star trail.

Several layers of images taken at intervals all set to blend mode “Lighten”

Align and Blend Stacking

Stacking can ALSO mean ALIGN and blend images with median, mean (aka average) or more sophisticated algorithms. Indeed astroimagers have been doing this style of blending for years using techniques that involve “star registration” (aligning stars with stars) and some pretty fancy stacking algorithms like Alpha-Kappa Median Clipping and Entropy Weighted Average. The key point here is the alignment. Indeed, here at StarCircleAcademy, we’ve explained how you can brighten and reduce noise in your foreground using simple astrophotography processing techniques.  See below for how to accomplish Align and Blend Stacking in Photoshop, and plenty of warnings about why this method is very likely to FAIL using Photoshop as the tool.

You may also see references to tracked, stacked images. These are the same as “align and blend” just described, except that to capture the image, the camera is guided by an external device (or by some fancy internal hardware), to allow longer exposures of the stars without getting unintentional trailing (smears) of stars.

The takeaway is that not all stacking is created equal. You need to know the context to understand what is meant by the word: stacking.

Focus Stacking / Auto Blend Layers

In Photoshop there is Edit -> Auto-Blend Layers -> Stack Images this is yet another kind of stacking (focus stacking) and despite the wording is NOT the kind of operation needed to ALIGN and Blend astro images. If you don’t believe us, give it a try and you’ll see it will do very weird things with your layers. Below are the same images as earlier. Note the bizarre masks it created to do the blending.

Edit -> Auto-Blend Layers -> Stack Images makes a mess. We told you so! Click to see a bigger image.


Aligned, Stacked Starry Landscape Images

While it would probably be better to make this a separate article in itself, we found it painful enough that we don’t recommend bothering – and yet we proceed to explain HOW to do it anyway!

If you want the cleanest possible images, you’ll – of course – want to reduce the overall noise  and bring out details by using many images instead of one. This approach is not all puppies and kittens. Here are some of the pitfalls:

  1. The direction of sky movement relative to the ground has a significant influence on the quality of the result (as well as the order chosen for alignment). In general, setting constellations are better than rising ones.
  2. Most of the existing tutorials will assume that you have a recent (CC) version of Photoshop with statistics and an an “Auto Align” that properly manages masked regions.
  3. Some of the tutorials we’ve observed are more cumbersome than they need be. There are plenty of hotkeys and mouse shortcuts to make the process go pretty quickly.
  4. More than 10 or so images can become quite demanding on machine resources.
  5. The complexity of your foreground will also affect the outcome. A clean, crisp separation between sky and land is preferable. Trees, poles, wires, and other things that extend through the sky are problematic.
  6. Lens distortion can also adversely affect the outcome.

Aligned Stacking Procedure

  1. Load all the photos as layers in Photoshop.
  2. Heal out airplane and satellite trails from each layer.
  3. Select all the layers and add to a group named “Sky
  4. Right click the Sky Group and duplicate the whole group as “Foreground”
  5. Select all the layers in Foreground.  Use Layer -> Smart Object -> Convert to Smart Object.
  6. Select Layer -> Smart Object -> Stack Mode -> Mean
  7. Duplicate Mean using Ctl-Alt-Shift-E (Command-Option-Shift-E on MAC). Label the newly created layer “Mean” and turn it off.
  8. Select all layers in Sky. Set blend mode to “Lighten” and observe the direction of star movement against the ground.
  9. Be sure the image with stars nearest the ground is at the BOTTOM of the stack. The bottom layer will be your base for alignment. You can drag layers around, or Layer -> Arrange -> Reverse may do the trick.
  10. Create a mask keeping as much of the sky as is easy to do but that DOESN’T include any ground  or fixed location objects. IMPORTANT: Be sure the mask doesn’t have holes in it, including at the bottom corners. Click the layer mask, hold down the Alt (Option) key and drag the mask to the next sky layer. Repeat until all sky images are masked with the same mask.
  11. Select the bottom layer and lock it  (Layers -> Lock Layers -> check Position -> Ok)
  12. Select all the sky layers.
  13. Chose Edit -> Auto Align Layers -> Auto
  14. When alignment is done, set blend mode for all sky layers to Darken. If stars are disappearing in the result image, that’s bad.
    1. If alignment is great everywhere, that is you have plenty of stars, you’re done. But it probably won’t be. So…
    2. Duplicate the current layers to a NEW document – call it whatever you want, but perhaps “Left looks good” makes sense.
    3. Open the history palette and click just above the “Align Layers” item (to restore to before the alignment was done). Lock the TOP layer (see item 11) and repeat steps 12-14.
    4. If a large portion of the image still has streaks in some quadrant, try undoing align, undoing the lock and re-aligning.
    5. If you’re still getting a significant amount of streaking you can also try Auto Align -> Reposition rather than auto.

      Q: Why do I have disappearing stars?
      A: The reason they are disappearing is because they are not aligned. In Darken mode, the darker sky “wins” out over the several stars. This COULD be a good thing in other situations, but not here!

      Q: If I went through the trouble of doing all this alignment, why is it still “off”?
      A: Photoshop isn’t optimized to align stars. Secondly, lens distortion makes a star move non-uniformly across the sensor. And third: stars at different declinations (celestial latitudes) travel at different speeds across the field. To eliminate streaks, the best solution is to track the sky.


  15. Take the aligned sky, delete all the layer masks. With all the aligned sky layers selected, create a smart Object.
  16. Do the same Stack Mode “Mean” trick for the sky smart object that you previously did for the foreground.
  17. The rest is pretty straight forward. Turn the foreground (mean) back on. Use a selection to reveal only the foreground and apply that to the Foreground Group.
  18. Adjust contrast, color balance, vibrance, etc. to your satisfaction.
  19. Save the kit and caboodle.

Does all this seem too complicated? Well, then perhaps you might consider using these tools instead. They do most of the hard work for you and they KNOW the difference between stars and foreground (usually because you help them know).

  • On a Mac: Starry Landscape Stacker – from the Mac App Store
  • On a PC: Sequator – do a Google Search to download it.

By the way there are many astro processing tools, like Deep Sky Stacker – but most/all of them expect that your images will have NO foreground or non-moving objects like wires in them.

Adding Special Touches to Your Astro Landscape

Published: November 6, 2107

1000 ISO, f/2, 3 minute exposure with some augmented stars

Because stars are pinpoints of light, the camera does not capture them as our eyes see them. To our eyes, brighter stars stand out more noticeably than dimmer ones. At a workshop in Alabama Hills, one of the participants, Julian Köpke, was using a diffusion filter so the stars captured would look more like you see with the naked eye. Sometimes nature provides its own diffusion filter in the form of high, thin cirrus clouds as shown below. The large bright orb is the star Sirius in the constellation Canus Major (Big Dog). The orange star near the top of the frame is Betelgeuse in the constellation Orion. One nice thing about the blur that the clouds added is the star color is more noticeable. But the diffusion here is not uniform because the belt stars (Alnitak, Alnilam and Mintaka) and “corner” stars (Bellatrix, Rigel, Saiph) in Orion are all noticeably brighter than the surrounding stars while in this photo only Betelgeuse and Rigel stand out.

Dog Star [C_065586]

You can create a make-shift diffusion filter by shooting through a nylon stocking – or buy a diffusion filter. The disadvantages of using a filter are that everything is blurred – including the foreground and you reduce the amount of light collected. Most night sky photographers try to avoid clouds and you will get an image like this:

The moon and Teapot Asterism in Sagittarius – over Lone Pine Peak – as shot.

When what you had in mind is something like this:

Same Photo as above, but with the Teapot Asterism in Sagittarius enhanced.

How to Bring Out Star Color And Enhance The Apparent Star Size

Our Advanced Stacker Plus has two built-in ways to increase star brightness. We call those Bump Up and Pump Up the stars. Bump Up creates a small blur by literally duplicating the shot , nudging the duplicate(s) and recombining .  Pump Up is more sophisticated and tries to find the stars so it can then apply enhancements to just the stars. But there is a new tool in the arsenal that I have begun using: Star Spikes Pro from ProDigital Software.  Version 4 is the latest as of this writing.

NOTE: Star Spikes Pro and HLVG described later are currently only available on Windows machines.

You can use the Star Spikes Pro plugin to add diffraction spikes and diffusion. The most common diffraction spikes you see with stars are due to obstructions in the telescope used to photograph them and many people come to think of the spikes as evidence of astrophotography.  You can create diffraction spikes easily on your own.- just stop down your aperture;  however stopping down to make stars create those spikes will not work well.

The first time I tried to use Star Spikes Pro it did not quite work as I expected.

Look hard. Star Spikes Pro decided the moon was a huge star outclassing all others.

Indeed it took me a bit to realize what was going on. The good news is it was easy to work around. The huge moon looks like a huge star to Star Spikes Pro – and that makes perfect sense since the plugin is usually used with Astrophotography that does not involve landscapes.

Here is how I made it work as I wanted and limited the effect to just the desired stars.

Layer Palette and Steps to Enhance The Teapot Asterism

Above left is the layer palette. Look carefully and you may spot the fix. After loading the image (1) I first duplicated the original and called the new layer Heal (2). I then did minor contrast adjustments, used the healing brush to remove hot pixels and other offenses (short satellite trail). Next I duplicated the Heal to another layer (3) and fed it into Hasta La Vista Green – a free plugin written by Rogelio Bernal Andreo of DeepSkyColors. HLVG removes green which is an unnatural sky color usually caused by RGB artifacts. HLVG operates on the entire layer and does not know the difference between land and sky. To leave the natural green in my landscape I used the quick selection tool, dragged it across the sky followed by Select -> Modify -> Expand 4 pixels. Then I created a Layer Mask using “Reveal Selection” (4). That made the foreground come back to its normal state. If you look carefully you will notice I also used a white brush to add some of that green removal back onto the mountain by painting on the HLVG layer mask (4).

The next operation was a finger twisting sequence that has no menu equivalent: Ctrl-Alt-Shift-E (on Mac that’s Command-Option-Shift-E). What that sequence does is “flatten” all the visible layers and create a NEW layer in the process (5). That layer I called Input to SSP.  Since I had discovered that Star Spikes Pro was confused by the moon (and could be confused by the foreground), I used the quick selection tool again and brushed it across the foreground. By default using the quick select tool again ADDs to the current selection so I brushed it around inside the moon and its halo. At this point I did not need to create another layer (Ctrl-J/Command-J or Duplicate Layer) but I did so that it was easy to see what happens next. After creating the new layer I selected it and used the delete key. Delete removes the selection making it transparent – that is the foreground and moon were now gone (6).

Next up: let Star Spikes Pro loose on the image. First deselect (Ctrl-D Command-D) or Select -> Deselect), and feed the sky layer to Star Spikes Pro via Filter -> ProDigital Software -> Star Spikes Pro.  The defaults for SSP produced the image below (I’ve zoomed in on the teapot asterism)

I felt the color was a bit too strong, and I did not want the diffraction spikes. The next step was to select “Advanced” – just below Settings, set the Primary quantity to zero. Next was the Secondary tab where I reduced the quantity to 44, the intensity I bumped up to 23. Soft flare I set quantity to 12, bumped up the intensity, dialed down the size a little and dialed down the Hue to -21. These adjustments were all based on eyeballing the image and were made for aesthetic appeal.  After all the adjustments looked about right, I saved the settings as a new adjustment I called “DiffusionOnly”. Finally I clicked OK and my layer was all nicely done by the SSP filter.

The filter processed a few more stars than I intended to augment. The simple solution was to create a “Reveal All Layer Mask”, select a brush, the color black and paint out all the effects I did not want on the layer mask (7).

The final operation was to use an Adjustment Layer (8) to increase the contrast and restrict that adjustment to the sky (where you see white) and tone the adjustment down a little with a low-flow back brush on one area that looked a little too dark.

The topmost layer in the layer palette is my watermark.

There Is An Easier Way!

With some experimentation, and some coaching from the plugin author I discovered that Star Spikes Pro has several features that make the process easier than I imagined. Instead of creating the transparency (deleting the moon and landscape) I only needed to select the area I wanted Star Spikes Pro to operate on.

Also, instead of masking off the stars I did not want affected after the fact, Star Spikes Pro has two tools to greatly simplify things the: “Hide” tool to turn off any effect that I did not want, and the “Show” tool to turn the effect on.

 

Star Spikes Pro limited to specific section of the sky via a selection and using the Hide tool to turn off an effect.

 

The net is that you can get that nice diffusion effect for your stars without having to compromise by shooting through a diffusion filter. However if you DO want to try a diffusion filter, I recommend you take two shots quickly. One with the filter off, one with the filter on. You can then place the diffused shot over the normal shot. Set the diffused shot to Lighten and mask in (or out) the areas where you want the diffusion to show through.

If you’re wondering whether there is a way to get the diffusion effect on a Mac or without purchasing Star Spikes Pro, there is, but it requires a lot of Photoshop twiddling and it is not anywhere near as pleasant as using ProDigital Software’s Star Spikes Pro.

Disclaimer and Book

I am not affiliated with ProDigital Sofware. I am a happy customer of Star Spikes Pro (and another product called Astronomy Tools). I was not paid, or encouraged to write about the product. I chose to because it is that good. Rogelio Bernal Andreo  author of Hasta La Vista Green and purveyor of DeepSkyColors is a friend and a multi-multi award-winning astrophotographer. He has a Kickstarter Project that I recommend you look into called Notes From the Stars

Notes from The Stars: 10 Award Winning Authors

Exploring Night Photography Lesson 5: Photo Processing

Published:  May 4, 2016
Last Update: May 10, 2016

Homework assignment: Star Trails. This was created using StarStax with 150 exposures of ISO 800, f/4, 15 seconds.

Homework assignment: Star Trails. This was created using StarStax with 270 exposures of ISO 800, f/4, 15 seconds. What are those things where the arrows are pointing, and what is the circled constellation?

Last week in lesson 4 the subject was star trails. We continue that theme this week and fill in with some material that you may have learned the hard way.

What settings?

Last week’s assignment was:

  • Weather Permitting, get at least 20 minutes worth of star trails. First determine what the best starting exposure is, then take 20 minutes worth.

I chose to take about 270, 15-second exposures at f/4, ISO 800 for my star trails using an intervalometer trick that I demonstrated in class. That nets over an hours worth of exposures. But how did I come up with those settings?  It was a little bit experience, and a little bit application of the principle taught in the very first homework: namely try and see!  But how did I decide what evening I would try to get star trails?  The weather needed to be right, so the germaine question is:

When will the weather be right for star trails?

Well, we strongly recommend weather.gov. See our article about how to use the information. Indeed, we like it so much, we even created a page with forecasts for places we often find ourselves going.

Weather, check. Settings, check. Now what?

Wait, what about the moon? We need to know when it rises and sets. A full moon washes out a lot of the night sky and makes for unpleasant star trails.  There are many places to determine what the moon situation is like, but I like to use The Photographer’s Ephemeris (either the App, or the online version).

Next we need to review the Stacker’s Checklist both to be sure we have all the gear and that we know what we are doing. Best is to run through it at home. Is it surprising that there are SO MANY steps? Sorry, but they are there to prevent you from making all the mistakes we’ve made.

In class we reviewed our homework (star trails) from the last assignment and discussed hits and misses.  Finally we got to the meat:

Photo Processing

It would be foolish to attempt to describe everything we did in class… especially since we have so many articles here describing how to photo process your shots (and webinars and recordings, too – oh my!)

But we demonstrated three things:

  1. Super simple Panorama creation using “Image Composite Editor” from Microsoft. Yep. You have to have a Windows machine to use it… but it’s free and SUPER simple and more effective than anything we’ve managed to get out of Photoshop or Lightroom.
  2. What Lightroom is good for… cataloging your images. And what it’s NOT good for: complex multi-image editing – for example star trails and image combinations.
  3. The three most powerful and useful elements of Photoshop:
    1.  Layers – This is the real meat of Photoshop together with blend modes which mathematically combine layers.
    2.  Masks – Masks allow you to change the way layers and adjustments get combined by “masking” out some of the changes.
    3.  Adjustments:  Curves – Curves are the best tool to learn since nearly everything you can do with the other tools can be done with curves… and if you get the hang of it, curves are actually easier to understand.

We also demonstrated Adobe Bridge which is a “lighter weight” version of Lightroom – one that doesn’t require any importing. And we spilled the beans that “Adobe Camera Raw” is the guts of Lightroom. And that Lightroom adjustments are really just like what you can do in Photoshop… with some of the magic, and much of the versatility – and also much of the complexity removed.

We also explained why RAW is the way to go, and why RAW is ugly (short reason: the camera does not see the way we do it just records heaps of numbers).

We did not do this in class, but we covered much of the ground:

12 Minute Star Trail using Advanced Stacker PLUS version14D from Steven Christenson on Vimeo.

 

Top Six Questions We Answered About Lightroom

  1.  If I use Lightroom to catalog and organize my images (keywords, etc) am I forever wedded to Lightroom?
    Practically, yes. We used to use Picasa and did our organizing and cataloging there…. unfortunately Picasa was discontinued and Lightroom had no way to import the data. If you stop paying for your Lightroom Cloud edition, you may be stuck as we do not know of a tool that can digest your Lightroom catalog.  SOLUTION: BUY Lightroom, don’t just subscribe. This is not so true about Photoshop, by the way, many tools can import Photoshop files.
  2. Is there anything particularly painful about Lightroom I should beware of?
    Yes. Lots! When your image library gets large, managing images is unwieldy, especially if you want to use multiple computers and multiple storage devices to hold those images.
  3. Is Lightroom good for Night Photography images?  Not particularly. Most of the power of manipulating night images is found in Photoshop (averaging, stacking, compositing). Lightroom can not composite images, for example.
  4. Is Lightroom hard to use? Yes. No. Maybe. We think it is powerful and much easier to use than Photoshop. But there is still lots of learning and ample room to do the wrong thing.
  5. Should I import everything I shoot?
    Yes… and No. The smaller the image library the easier it is to keep organized. Of course if you delete the very images you later want you will have paid a price for your anti-hoarding behavior.  We do believe it is reasonable to throw away .JPGs if you are keeping the RAW files. And those fringe images that you are likely to never use – well you are likely to never need them.
  6. Can I do everything in Photoshop that I can in Lightroom?  Yes, mostly. Photoshop has no image organization tools, but yes, you can make all the adjustments in Photoshop that you can do in Lightroom… only it will be harder to do and may be harder to apply to multiple images at once.

Oh, by the way, the official name of Lightroom is “Adobe Photoshop Lightroom” just to confuse everyone.

What Are the Top 4 Things to Know About Photoshop?

  1.  Photoshop is the lingua franca of photo editors. Nearly every other tool does not come close in the level of acceptance and use. Widespread use does not mean Photoshop is the best tool. Remember how VHS beat Beta? These days video tape is hardly even used! Photoshop has been around a long time and has a LOT of baggage. Photoshop is built to do a lot of things way beyond photo editing (scientific analysis, animation, typography to name a few). Because Photoshop has been around so long, the tooling is unnatural .  We started with Paint Shop Pro and found it much, much less confusing.
  2.  Is there an alternative to Photoshop?
    Yes, there is the free Gimp, and many others. Unfortunately as we have noted above, those tools are not as widely used so getting help with them is harder.
  3.  Do you have any suggestions on what I should learn first?
    Why yes, thanks for asking. We have a series of articles on that:  We call the series “The Most Used Image Editing Techniques” and it comes in three parts: Part 1, Part 2, and Part 3.  The one we used the most is the “Simple Astrophotography” Trick to reduce noise.  We also like this trick to select a foreground (it’s used in the video above) and use it a lot.

Homework Assignment

  •  Fire up Photoshop and try to duplicate this image:
Final image with replaced foreground

Final image with replaced foreground

Super big hint… all the files you need and the process to accomplish the task is described in this article: Foreground-o-Matic.

  • Use the same technique on your own image(s) to pick a more interesting foreground image from a “stack” (sequence) of images.

Feel free to comment below if you know the answers to the questions we asked in the first image above. We will reveal the answers in the next article.

Bad Bridge Behavior (2014)

This discussion applies to Windows machines in particular. We welcome your comments on whether the same problem occurs on Macs.

In Summary

Installing Photoshop CC 2014 on a Windows machine may have unpleasant side effects and one of those side effects is being forced to use ONLY Photoshop CC 2014 from Adobe Bridge.

The Details

Adobe Bridge is a rather powerful tool. In fact, we recommend it when using the Advanced Stacker PLUS. However during a live webinar recently Bridge stymied us.

Despite the release of many CC 2014 versions, there is currently no Adobe Bridge CC 2014 – the latest available is CC. Within Adobe Bridge CC a double click of a JPG or RAW file opens the file clicked in the most recently installed version of Photoshop EXCEPT if there is already a version of Photoshop running. If, for example you have Photoshop CS5 running and the most recent install is CC, then a double click would open the file in CS5 rather than CC. Adobe Bridge default file open still behaves the same way even after upgrading to Photoshop CC 2014. However other parts of Adobe Bridge do not behave the same.

The Tools -> Photoshop -> Batch operation previously worked just as described. No matter what the default version of Photoshop, using the Tools -> option would kick the currently running Photoshop and elicit Photoshop’s Batch menu. UNFORTUNATELY, The “Tools -> Photoshop -> Batch” operation does NOT work the same way once you install Photoshop 2014 CC.  With Photoshop CC 2014 installed, Tools -> Photoshop -> Batch will ONLY open Photoshop CC 2014. If you have another version of Photoshop already running, the Tools operation effort silently fails.

You can determine what version of Photoshop will be invoked by the Bridge -> Tools menu by selecting a file and doing  a “right click” and inspecting what is listed in the Open With list.

Default association

Default association

 

Also particularly unpleasant is the fact that only ONE of the Photoshop CS versions is listed as a choice in the Open With dialog even though on our windows machine we have 4 versions of Photoshop installed (CS5, CS6, CC and CC 2014). We’d love it if we could choose which Photoshop to open, but Photoshop CC 2014 confuses Windows into thinking that ALL versions of Photoshop are CS 2014. Normally in the the windows file browser you can right-click a file and “choose a default” program to open it.

Windows_ChooseDefaultPgm

Here we’ve chosen to associate a default to a PNG file.

Window_FileAssociation_Step1 The next step is to navigate to the program we want to open with by default… Here we will select the Photoshop CS5 folder, and next the photoshop.exe
Windows_SelectAssociation

After selecting photoshop.exe in the CS5 directory, we are disappointed to see the result look like this:WindowsPSCC2014_Confused

To Change Associations For Different File Types

While Photoshop does continue to make useful improvements, not all of those improvements are as easy to navigate. If you would prefer that Adobe Bridge open a different default version of Photoshop you can change the file associations within Adobe Bridge as shown. (Select Edit -> Preferences or Ctl-K).

Changing File Association

Changing File Association – click for a larger view