Photo How-To 1 – Sequence Shots

22 07 2009

Hi all,
When making the shot of Tim yesterday I was experimenting a lot with how it could be done and what steps were required in Photoshop to make it happen. After thinking about it a bit I thought that it might be a cool exercise to write up what I did and in the process learn how to write how-tos of the sort seen on digital-photography-school.com. Although I don’t have delusions of being at that level :-)

DISCLAIMER: I’m only a beginner, both at photography and Photoshop and so everything I write here should be taken with a grain of salt.

As I said in the post yesterday, the aim is to create sequence shots like those used in ski and snowboard magazines, an example of which can be found here: http://www.flickr.com/photos/thomasroed/2274197627/sizes/o/

Step 1 – Take the shots


On the last day in Savai’i, Samoa we stopped at a fresh water waterfall with a cliff jump for a cool off. I tried to take several series of shots of Tim and Dad jumping off with the intent that they would become a sequence.

When shooting you should frame the shot so that the action will occur well inside the frame as you don’t want to move the camera during the action and therefore change the view point as parallax and the like will change the arrangement and relative position of things. If needed you can always crop away area later on but it is kind of annoying if you miss the edge of the action because it goes out of frame.

Ideally you should use a tripod while taking the shots so they are perfectly aligned but I just handheld and used Photoshop to align the images which works well enough that it doesn’t matter too much.

You’ll also want to use as fast a shutter speed as is reasonable to capture the action and to manually focus on the plane the action is taking place to avoid differently focused images. As such the aperture should be small enough so the hyperfocal distance includes all the action. Unfortunately, even though the action was happening on one plane so I could use a wide aperture of f4.0 the lighting was too low to support a shutter speed faster than 1/50s at ISO 400 so there is a lot of blurring.

I also found that because it took longer than 1/10 second (5 shots at 1/50s) for the entire jump it wasn’t possible to use continuous mode as the buffer would fill before the splash and the camera would slow considerably. Of course this would be even worse with faster shutter speeds. As a result I started to intermittently press the shutter so the time between shots was longer. This means more movement in the camera and less regular timings but means a complete sample of the action is taken.

Step 1 - Take the shots

Step 1 - Take the shots

Step 2 – Align Layers


The next step is to get them into Photoshop. Make sure that the same white balance is used in the conversion process but it doesn’t matter so much about the exposure as this will be corrected later. Open each image then paste them into separate layers of the same document. Select all layers then, if the shots were taken handheld, use the Auto-Align feature to align them properly.

Edit->Auto Align Layers

Step 2 - Aligned Layers

Step 2 - Aligned Layers

Step 3 – Exposure Compensation


Because things change from moment to moment there will be slight variations in the exposure of each image. To make the blending more accurate it’s a good idea to compensate for these differences. To do this I first chose the ‘master layer’ where most of the image will come from. In this case it was pretty easy because the splash held a lot more detail than the other layers that would be difficult to mask later. For every other layer I then created a layer mask that was half hide and half reveal.

  1. Layer->Layer Mask->Hide All
  2. Rectangular Marquee
  3. Select half the layer mask
  4. Fill with white
Step 3 - Exposure Compensation

Step 3 - Exposure Compensation

This makes it easy to see the difference between each layer’s exposure and each can be tweaked to match the ‘master’ layer.

Image->Adjustments->Exposure

This done we can remove the masks and are ready to move on to compositing the bits together.

Step 4 – Organize Composition


Next we need to organize which order to layer things. This is important if there is overlap in any of the frames as there was in my case where the splash and the shot just before entering the water were overlapped. To make things more complicated I had a problem that the splash should be over the previous frame but the splash was needed as the master image because it had more detail than the others and masking would be hard.

To get around this I did a selective select on the splash, copied this to a new layer, and then put this over the top of the other shot Because the splash was white this was reasonably easy using a ‘Color Range’ selection:

Select->Color Range

Then choose a fuzziness that selects enough of the splash but not the background, copy and paste into a new layer.

Step 4 - Arrange Composition

Step 4 - Arrange Composition

Step 5 – Mask Images


The final step is to selectively mask in the areas of each frame that we are interested in and merge them into the final image. Turning off all but one layer you can mask in the relevant area by creating a layer mask and selecting the relevant area then ‘cutting it out’ of the layer mask.

  1. Layer->Layer Mask->Hide All
  2. Disable Mask (hint: shift+click on mask)
  3. Make sure Layer Mask is selected
  4. Use magnetic lasso to select around area of interest
  5. Fill with white
  6. Re-enable Mask
Step 5 - Mask each layer

Step 5 - Mask each layer

This should make the area you want be visible over the master layer. By doing this for each layer you will end up with just the action areas composited over the master layer, and because the layers are aligned the area around each bit of action or any objects that pass in front should fit with the background nicely.

If you want you can tweak the exposure, contrast and colour of each layer to make it fit better or stand out from the background more to taste. Finally we can merge all the layers together and we have the final image.

Final Image


Tim at the waterfall (5 shots f4.0 1/50 40mm)

Tim at the waterfall (5 shots f4.0 1/50 40mm)

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One response

24 07 2009
Mum

awesome! May bring back slightly painful memories for Mark – he still has bruising from his last jump.

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