Tag Archives: PTGui

Creating a Night Panorama

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Asylum at the Sea

That’s it. You just found the perfect composition but there is a problem. The interesting bit does not fit with the other interesting bits.  So you sacrifice and change to a wider angle lens but that does not improve the shot. In fact, you can’t get an image wide enough or tall enough. Let’s change our frame of reference for a moment because not many people think about the ability of panoramas to connect the foreground to the heavens.

Although taking truly panoramic star circles is next to impossible within a reasonable budget, you can connect the earth with the sky with a little bit of planning and some tricks to aid in your alignment later in the process.

We are proposing a vertorama that is a “vertical panorama” to extend our photo to the ground and blend it into the star trail on top.  Our approach will be to shoot in landscape mode and tilt our camera up as we progress.   We can take a series of two or three shots but it will look odd if the star trails don’t extend into the edges of solid land (lower portions).  We also have to make sure that we don’t end the last frame too high as this leaves the star trail disconnected from the ground (lower) images.

Gear

The minimum amount of gear required is a camera a tripod and an interval timer.  However the whole process is going to get much easier if we have a method to align the “no parallax point” with the axis of rotation.  Huh? What did you just say…If you didn’t get that last sentence I suggest you read our primer articles on panoramas here and here or by following links out to other resources.

Planning a Shot

By this time I am assuming that you have read all of the prior articles on shot planning and alignment.  If not they can be found here, here, and here.  Now that we are up to date on planning and alignment we can get into the gory details. We are going to have to take some additional steps to help in the alignment in post processing.

I can get obsessive about the details but I want to do it right not get back to my computer to discover I spent 4 hours in the cold, dark night with stars and nothing interesting in the foreground.  I begin with an idea of how I want the image to look then I walk around with a compass and the local north declination adjustment to fine tune where the center of rotation will be in my final image. I set up my tripod where my chosen foreground will be in  alignment with Polaris (aka The North Star). Before I take the first photo I know where Polaris is going to appear in my frame. When I am really particular I will use a laser line to insure I have the object exactly where I want it in the photo.  I then level the tripod and assemble the pano head.  I use the pano head to determine the elevation of the north star this helps me know exactly how high the star with be in the sky.  This helps me to see where the star circle is going to be in the photo.  [Editor’s comment: If you know the angle of view of your lens you can determine the altitude of the north star by using your camera’s field of view as a measurement]. Knowing how high Polaris is in the sky will help me to determine the overlap I need to include all of the elements in the photo I want.  This all may seem like over-kill but to go home and thinking you have an image of a lifetime only to find you have a dud is not fun.

Shooting (and Bracketing)

I take a lot of photos with different settings until the blue period ends and the stars begin to appear. I make sure that I take a lot of bracketed shots that have 30% to 50%  of overlap. Having plenty for foreground images to choose from later is going to be very helpful when merging the final images.   Once I am satisfied I have enough images the next step is to lock the camera and tripod down tight to take the series of star trail photos.  If I didn’t get to my intended location in time and still want to get foreground shots it is still possible. Darkness merely means that my foreground exposures are going to have to be long, perhaps very long. Alternatively I can light the foreground with a flash light, strobe, or fire or I will let you borrow some light from my moon. 🙂

These are some of the images the top and bottom of the vertorama. I took right before the blue period ended. You can see the various bracketing and over lapping I did.

 

Post Process

I assume that you already know how to process your star shots into star trails. If you need a refresher check out Steven’s articles on star trail creation.  I like to do a few different versions of the with stars because I like to include different amounts of blue and so I have an easier time blending them in later in the stitching process.

Just some of the Star Circles I generated using different amounts of blue period photos.Combining a star circle with a foreground can be done with several different stitching engines, I prefer PTgui, however for other stitching engines the workflow is similar. Your images may be bright enough to do the whole process with Photoshop’s stitching or in Microsoft ICE engine but if you are blending in photos to get a darker sky then Photoshop might be a dud.  Also these stitching programs will not allow you to add control points to help align and warp the image to the background and let me be the first to  say the alignment and warping the foreground image is not fun or easy.

Import your Images

I like to import a lot of different bracketed images into the stitching engine just so I can have some variety to work with.  Also it will allow me the automatically find control points on overlapping images and then tell the software that the other images have zero pixel shift from that image in the bracket series.  This allows me to save time by putting control points on only the images that are dark or match the star circle image.   Thus I can align and blend the pano in one step then use Photoshop to blend in the stars.

Once imported click the align images,  did it work…if so hooray!! You now only have a small amount of clean up to do (skip down to the projection part of the article).  If not then you have to add some control points and align the images yourself.  Control points are areas on an image that match in overlapping images the software needs to know these areas to know how to warp adjacent images to stitch them together.  So lets look at how PTgui does this.  Below is a screen shot of PTgui’s control point placement feature.

Control points selected between the star circle image and the bright forground image. I pick areas in the image that have 1) sharp contrast, 2) Jagged edges and 3) don’t move.

All you have to do is open the adjacent images at the seam and then zoom in to find distinct points that match.  I like to use object with good contrast and unique shapes to help guide my cursor to a pixel accurate match.

In the image above you can see that the transition between the rock and the sky is the area of overlap.  I follow the rock edge because of the contrast between the sky and the rock but also it has bumps that are easily distinguishable between the top and the bottom photos. Once I have these set I do the same for the star trail photo see below.

Aligning the Star trail image with the photos from the blue period

I will align the star circle photo with the corresponding photo of my foreground just so I have less stitching errors and it is easier to align.  Again if the star circle is light enough then these images may automatically align.

Projection and orientation

Once all of the images have control points then I will go and see how the preview of the image looks in the panorama editor.

Looking at the stiched images in the panorama editor for the first time to see the errors in overlap and the corrections needed to correct the distortion.

You can see the top and bottom images of the vertorama are properly aligned at this point don’t worry about the blending we will handle that later in photoshop.  Two things are very off, causing distortion of the star circle 1) the projection and the vertical height of the image.  The projection is the way the images are projected on to the inside of a sphere during the alignment.  If you are interested in the types of projections  (and there are many in the image below) and how the distortion affects the overlap and warping of your image more info can be found here. I am not interested in the type or how it works in this case I am just worried about what looks right.  For most vertorama star circle images the “Rectilinear” projection often looks the best but is not always the case.

Correcting the projetion to make the photo appear flat and not as distorted at the edges.

We can quickly correct the oblong star circle by moving the top image toward the bottom. This will change the amount of space that is blank but once we crop the image those areas will not longer be visible anyway.

Changed to rectilinear and moved the whole image down. You can see I changed the vertical FOV with the slider on the right (right red arrow) I changed the projection at the top to rectilinear. and the line in the middle shows the movement of the image down.

 Outputting the files

Once you are satisfied with the preview the next step is to use the image optimizer to hone the control points to reduce the error.  It is so easy I am not even going to include a photo just click and tab and click optimize.  It will give you a rating “very good”, “good”, “not bad”, etc.  then suggest some corrections my usual experience is just accept them they more often help then harm.

The only step left is the output the files and then mask them in photoshop.  Go to the “Create Panorama” tab and preview the settings.  You can see the settings I use is to output the images as a “.psb” for use in photoshop but you can output what ever you would like.  The most important is to output into 16bit layers under the “LDR file format” or “HDR file format” settings. This is shown in the screen shot below.   Since the blending is going to  cancel out some of the stars the aligned images need to be output in seperate files so.  I will uncheck the image that represents the aligned star circle in the screen shot below this is “Image 6” the rest of the images are the aligned HDR brackets.  Then I will name the file something like “file….SC_BKGD” were file is the former file name and the “SC_BKGD” stands for “Star circle Background”.

Outputing the top and bottom layers

Once this is done stitching I output the star circle image alone.  So in this example I would un-check the boxes next to images 0-5 and only output image 6.   So once all of these images are outputted I select them and open them as layers in photo shop.  If your blending went well in PTgui then  great skip the next step and forward on to the next.  If the blending shows seams or other artifacts of stitching follow then next steps.

If the blending was bad then go back to PTgui mask out the areas the blending did not work so well if you have PTgui version 9, if not then output all of the layers and we will mask and clone in photoshop.  I picked this example specially because I had blending issues in the past so if you have blending issues you will know how to approach them.

This is my stitched Foreground and star circle images notice the two red arrows are places where the blending did not work so well

The first thing to try since the layers are aligned is the auto blend layers under the Edit menu.  Select the top and the bottom then navigate up to “Edit” and click under “auto blend layers”

 

This is the first tool I reach for when blending is the auto blend layers. Once the layers are aligned (and HDR-processed) thanks to PTgui the blending in Photoshop is usually easy.

If the auto blend function does not work it is time for some good old fashion hand blending. I will open the individual blend layers and the PTgui blended photo with blending issues.  I will use the photo with blending issues as the background and layer over the top the individual planes to blend by using a mask to gradually make the layers more transparent using a big soft brush.  I slowly make the seam fade or use the surrounding colors to add detail.  I will also use the clone stamp to replicate areas like clouds and blend them into each other.  This takes a lot of patience and practice to make some areas look “normal” but keep zooming in and out to see what affect you are having on the whole photo and local areas.

Adding the Star Circle

Once the blending the top and bottom image is finished the star circle can be added.  Since you exported it as a separate layer out of PTgui this can be brought into photoshop as a layer in the document.  Opening the photo as a layer then by changing its blend mode to lighten or screen blend mode then bright stars will out shine the dark background.  Thus adding the star circle to the finished photo was easy.  Don’t forget to mask out some of the areas were affected by the screen blend.  Say in cases of light pollution the foreground might be brighter then they should be.  Crop then your done.

Final image

This is the final image after the stars are added as a background layer and blended in using the screen blend mode.

Thanks for reading, as always comments and questions are encouraged.  If you have found this interesting please forward to your friends and follow us on Facebook. If you are interested in this topic (panoramas), night photography, shot planning, or super cool post processing techniques come and join us for a workshop.

 

Improving Your Panoramas

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Hi, I am Eric Harness, one of the instructors of Star Circle Academy. I want to first thank Steven for the great intro, also for his inspiration and his mentorship.

Steven asked me to add some important details to his Panorama Pursuit article.  So here I will expand on the information that Steven described by adding important panorama setup considerations, shooting tips and my work flow.

Panorama’s give the viewer context and detail that is not possible with standard photo sizes.  So use this to your advantage to show the viewer interesting elements to heighten the scene.   A scene worthy of shooting is worth the effort to set up the shot properly.  Seek wide open spaces where the relationship between elements gives an emotional connection to the place or thing.  A lot of landscape photographers like to exclude human elements in landscapes. However, including people, cars, and other human sized things helps to pull your viewer into the scene.   Park your car on the rock, leave the door open, have your friends pose looking into the scene.  Just make sure you connect the people in the scene to the rest of the scene. Highlight their interest or the viewer will not be interested at all.

People stop to look at what others are looking at all the time.  Let me give you a great example.  I often visit a large national park and I will often stop to photograph the animals on the side of the road.  I stop and ask my passenger to point out the window. Or for even more effect I have my passenger a poke big lens out the window even when there is nothing there!  People behind us stop and look while I slowly creep away.  This happens all the time – not just in the park but also at the mall, or art gallery, or along the road.  I use this natural human curiosity to look at what others are looking at to my advantage and put these on-lookers in my panorama!

Setting Up the Shot – The Tripod

It may seem like an after thought but once you bump your tripod in the middle of a panorama shoot you will be reminded about the importance of your base.  All of the elements depend on having a solid base so spend careful time to set it up.

  1. Extend the legs in a manner that allows the head to be as level as possible.
  2. Spread the legs so that the weight of the head and camera is over the center of gravity of tripod.

Even if you are not using a pano head the extra effort will help preserve the edges of your image (trust me it looks like your camera is on a roller coaster when it is not done correctly).

This multi-row panorama was not leveled before the intial shooting. The fix at this stage is to crop or fill but in this instance would make the image un-usable.

 

 

 

 

 

 

 

Any wiggle in the base will cause tiny misalignments in your images which can cause blurry stitches or fuzzy images (especially for HDR panoramas).

Managing Subject Distance and Parallax

Parallax errors occur when close and far objects shift in the frame relative to one another. This problem occurs when the camera is not rotated around the optical center of the lens.  The shift between close and far objects in more noticeable than the shift between two objects that are far away. If you keep all elements – especially important subjects – far enough away you will be less likely to encounter parallax error. Like Steven, I am not about to jump into the fray over the terminology wars over “nodal point” or “No Parallax Point” discussion.  However for an example of parallax error have a look at Figure 1 and Figure 2 below. Figure 1 shows proper alignment on the “no parallax point”, while Figure 2 shows how parallax results in an inconsistency.

Figure 1: These two images resulted after rotation around the "No Parallax point". Note how the foreground bars align with the same background objects.

If the lens rotation is NOT made around the “no parallax point”, then foreground and background objects shift as shown in Figure 2.

Figure 2: Two adjacent images with parallax - Note where the middle bars appear in relation to the steps behind them.

Alain Hamblenne has written an excellent article about how to align a panorama head in the horizontal and vertical directions. Note that Mr. Hamblenne refers to the no parallax point as “the entrance pupil“.  Even if you do not have a panorama head, the procedure Mr. Hamblenne describes will help to determine where the best center of rotation is. If you are lucky – as Steven was – you may find that your lens ring mount is almost the perfect place. Rotation around the tripod mount point in the camera is almost certainly not the best point.

Focusing for a Panorama

Focusing is not that hard in my opinion; just know your hyperfocal distance!  Yes, learn it for your lenses at different F-stops. Get out the tape measure and start pixel peeping.  Look up the resources on the web (DOFMaster) and learn to tell the distance by eye and turn off auto focus, then manually focus the lens.  Ok, focus done!  Furthermore, if you are doing this at night no worries you know if by heart if you don’t then turn on the million candle power flashlight (your cheater to activate your autofocus in the dark, then turn  autofocus off).

Getting the Proper Exposure Range

Let me first cover why I do HDR (High Dynamic Range) Panoramas. There are generally two reasons 1) the Sun, 2) your camera sensor.  Most panoramas span a large tonal range because of the directional light from the sun thus one edge might have a different exposure value then the opposite edge.  To make it even more difficult your camera’s sensor is not capable of capturing that level of tonal range in one photo.  Thus we take multiple exposures (bracketing) to capture a wider tonal range to represent what was really there.  Now that we have explained why bracketing for an HDR is important it is critical to determine the proper exposure range. Since the scene may span the tonal range from a dark canyon to a bright sunny area getting the proper exposure range is important.  There is no camera capable of capturing such a wide range of tones in a single photo.  But how do you decide the exposure range of the bracket and where the middle exposure is?  This is the method I recommend: Set the camera to Aperture priority mode and set the metering mode to a single meter point.  Then swivel the camera to some of the brightest and darkest areas in the range of your panorama. Then average the highest and lowest limits to select the middle of the range and then select bracketing that will encompass the approximately the whole range.    Remember to switch back to Manual mode and set the exposure to the middle of the range and select your bracket.  Typically as Steven suggests a two exposure bracket on either side of your middle will give you enough exposure range for most HDR panoramas.  I will typically set my bracket at a full stop and take a range of five exposures for my HDR.

Here is an example of calculating the proper exposure. Assume the darkest area of your panorama meters at 1/30 of a second at f/9. And the brightest area meters at 1/300 of a second.  30+300 = 330 and half of that is 165, so the middle of the exposure is about 1/160th – or whatever is closest. That’s not too wide a range. From 1/160th  plus and minus two stops covers both 1/30 and 1/300th.

Shooting and Overlap

Now your camera is set up for taking the photos but where should you start?  Some people use the degree scales on the tripod head to determine the overlap but I don’t recommend this.  Why?…well by not seeing what is in the photo you can’t determine if there is enough detail for the software you will later use to detect the overlapping elements in the photo.  Areas with large expanses of water or sky have little detail and will be hard to stitch.  The overlap I recommend is 30% to 50% but I have been forced to use 10% in areas of sky between trees.

I have to first decide where to start and end, what direction do I go.  I look at what I want on the edges of my panorama the I pick something further out then that to start and stop at.  If I want to include the top of a peak then  I will make sure to include some buffer in case I need to do some cropping.  Therefore, I will pick a solid landmark like a distinctive tree I call these left and right anchor.  This element usually will run vertical through the frame so I will run into it if I do a multi-row panorama.   I will center this object then I will I always start from the first frame at the left and go right just for consistency.  If I am doing a multi-row panorama I usually place the horizon on the lower third of the image to maximize the amount of sky I can get  but I always start from the bottom left then march to the right till the anchor is well within my frame the I tilt the camera up to capture the next row proceeding right to left till I reach my anchor then move the camera up again and proceed left to right again.

The first photo usually take in a set is a simple shot of my hand to indicate that this is the beginning of a new pano.  I cannot tell you how many times this has come in handy in determining quickly where the shots from one pano end and the next begin.  Also it help me to quickly group the photos so I do go through my photos say “that’s a crappy photo—delete” then only to realize it was the middle of a panorama (I have done that).

How do I take the photos so I don’t miss a photo in the bracket and keep my photos aligned?  I use continuous release mode and remote release to lock the shutter to shoot all the images in the bracket before I look in the view finder to align the next set in the panorama.  This allows me to pay attention to the things around me like people moving into the shot or time the shots to avoid the wind instead of counting shots.

Automated HDR and Stitching – PTgui

As Steven suggested use your favorite HDR program and stitching engine to combine the images.  I recommend using PTgui because of the enormous amount of control and power.  But there are other stitching engines out there: Autopano, Microsoft ICE,  Photoshop, HUGin and the list goes on.  I use PTgui because I can HDR and stitch all at once. PTgui can run in batch modes to automatically identify which images belong in a single pano and start the stitching.  In the newest version of PTgui you can zoom in on the preview panorama, mask out the “unwanted tourist” and preview your stitch lines.  The software also allows you to output the images in the set as a photoshop “.pdb” file in layers or the entire blend and stitched panorama.  Thus you can fix certain elements of the photo like shaking branches or moving people. All of the dedicated stitching engines PTgui, Autopano, and Hugin allow you to take full control and stitch low contrast photos by adding control points to the elements that match in your overlapping areas telling the software these areas are the same.  Control points help the software to match corresponding points despite any distortion caused by the lens.  Manual alignment is not possible in Photoshop CS5 or Microsoft ICE.  PTgui control points are a huge advantage in aligning stubborn images with little detail.  Find some details that overlap and are easily recognizable in the two photos zoom in and click on the pixels that represent the same object in each photo. I like to use distinctive branches, tips of trees or jagged mountain tops; something that has a sharp edge and will be easy to match the pixels in the other photo.  Once a few manual control points are added the software takes over and starts aligning the matching points automatically.  With a sufficient number of control points the software can use the information to warp and stitch the images into the final panorama.

 

Manual Processing HDR then Stitching

If you don’t have an engine that can handle both HDR mapping and stitching at the same time no worries you just have a few more steps.

First do HDR blending using the images of your main subject, meaning the people or the thing you are using to draw your viewer into the photo. Save the HDR settings for the main subject and process the rest of the bracketed images using the saved settings.  Doing HDR blending first and then stitching is much less error prone than stitching first and then blending.

Once the blending is to your liking drag the blended images into the stitching engine and let the software do the rest of the work.

What About Stitching Night Images?

If night images are what you want to stitch, please stay tuned as the next article will cover panoramas in your night photography.

Resources

Finally let me point you to fantastic resource for more on panoramic imaging.  Panoguide – a forum for panoramic imaging.  Panoguide is a in-depth discussion of the hows and whys of panoramic photography. They have an expansive “How to section”.

Thanks for reading, as always comments and questions are encouraged.  If you have found this interesting please forward to your friends and follow us on Facebook. If you are interested in this topic (panoramas), night photography, shot planning, or super cool post processing techniques come and join us for a workshop.