Photoshop – Smart Objects

4 02 2012

Since I’m on a roll, I’ve got a few minutes, and I’m in the middle of processing some digital photos that I’ve took, I thought I’d write another little post about something else Photoshop related…Smart Objects.  I’m going to hit on 2 main pieces of Smart Objects during this post, first using smart objects as a way to create embedded and easily update-able images in Photoshop or Illustrator files in Photoshop, second using multiple images to create make a busy street appear empty by using stack modes.

Smart Objects as links:

As I mentioned in my previous post today, shrinking an image or layer down and then enlarging it forces Photoshop to lose a lot of valuable data but then guess to try to make up for the lost data.  Is there a way around this?  YES!  Smart Objects create embedded Photoshop files within a Photoshop file.  How does this work?

To create a Smart Object, open the image and go to Layer>Smart Object>Convert to Smart Objects

The Smart Object is now created, you can tell because the layer will have a new black box in the preview of the layer.  When the Smart Objects are created, create a new layer and make some changes on the new layer.

Now we’ll make changes to the original image and watch it update.  Double Click on the layer containing the Smart Object to open it.  the following message will pop up:

Notice you can tell you’re working in the Smart Object because you’ll see the tab at the top is a .PSB file.  To create a noticeable difference, I’ll invert the original image and then save it again.

When you save the original layer again, close it and look at the update automatically made to the previous .PSD file.

Through this technique you can work in multiple layers and multiple files to ensure maximum flexibility while working!  The other great thing about this is the non-destructive to the original image.  The other cool thing about this is the way that you can use Illustrator files as Smart Objects in Photoshop.  For more on this, check out Colin Smith’s video via

Stack Modes:

So often times you’ll be out taking some photos and want a nice shot of a building, but there are people who are walking by, cars driving, or other things that happen to be bothersome to your artistic vision.  Well now with the use of Smart Objects, we can eliminate anything that’s moved throughout the sequence of images.  Using this technique is fairly simple, but takes a bit of forethought when actually taking the photos.

1) If possible use a tripod to stead the photos.  If not tripod is around, that’s ok, Photoshop can guess and try to align them, just don’t move!  Try to take a set of images in succession without moving, looking down, or shifting your camera.

2) Take multiple images and allow some time in between images.  This will certainly help when we get into the Photoshopping process because of the algorithm used to eliminate the moving objects.

3) Be artistic and have fun with it.  Don’t forget to experiment and see what cool images and post processing you can create!

I must admit that I stole this technique from Scott Onstott’s tutorial years ago.  I’ve taken a few images of a neighborhood here in Cleveland and will be using them as the basis for this exploration.


Once you get back to your computer (and defrosted in my case) download the images and then we’ll look at post-processing.  There’s two ways to create the Stacked Mode Smart Objects.

The first way is to open all the images of a single sequence in Photoshop.  Go to File>Scripts>Load Files into Stack

When the Load Layers Dialogue appears, select Add Open Files (or Browse and select Files…this is the second way of creating stacks)  Ensure that the check box for “Create Smart Object after Loading Layers” is checked.  If you didn’t use a tripod (or if you did and just want to ensure alignment) select “Attempt to Automatically Align Source Images”.

You will then most likely have time to go to the bathroom, get some coffee, or change the laundry out as it processes.  When it’s done you’ll see the stacked images on top of each other.

Notice the Smart Object icon in the layer palette.

Once the stack is created is as simple as going to Layer>Smart Objects>Stack Mode>Median.

Again, it’s time to get some coffee, change the laundry, go to the bathroom, or whichever you didn’t just do 5 minutes ago.  When you come back, you should a much cleaner version of the sequence.

Stacked Sequence - Median - click for full size image

The way that this works that Photoshop looks at all the images and only keeps the pixels that are the same in 50% or more of the images.  This is why it’s generally good to wait a second or two between images.  As you can tell, I was not so patient and while the car in the middle of the scene has vanished, the turning van on the right has created a bit of a trail.  It looks pretty cool, but the van certainly doesn’t create as clean of an image as I’d have liked, so next time I should take more time between images, or I could try with less images, for example the first image(DSCN007.jpeg), the middle image (DSCN011.jpeg), and the last image (DSCN014.jpeg).  Note:  I haven’t tried this for the sequence above, so I’m not sure if it will work, but sometimes it’s worth a shot.

Now that we’ve cleaned up the image, experiment with some of the other stack modes!








Standard Deviation




DPI and Output Size – what you need to know

4 02 2012

Ok, so I know that I promised I’d come up with a post about how to pull all the previous discussed techniques together, and trust me, I will.  However a conversation at the office yesterday arose and I thought it’d be a really good thing to post about…output size and how large should we be saving our images.

Keys to remember:

1)   It’s all about pixels!

Remember this, as it’s very important and the common factor between most of what we’ll talk about for the rest of the post.

2)  There’s going to need to be a bit of math, but trust me…it’s not that hard.

Go back to your days of Algebra I and you’ll be fine.  We’ll be using the equation DPI * Inches = Pixels.  From this equation, if we have 2 of the 3 variables, we can always solve for the other.  More on this to come later.

3)  It’s about the distance at which the object is going to be seen.

The human eye can differentiate pixels at about 120-150 dpi when being held and read in one’s hand.  As you step further away, less definition is needed.  Think about those various pixelated images that when you get close you see they are a montage of small pictures, but when you stand back appear to be one image.  This is exactly the same principle.

Image courtesy of Sabri Farouki at

Also, as you get older and are in lower light, you will be able to differentiate less dpi.  The other thing to keep in mind is that vector based information done in a raster based program will show effects dependent on the dpi.  The best example of this is text in Photoshop.  While working with a 72 dpi image, the text will look fairly pixelated and jagged.  The reason is because the linework of the font has to fit within the pixel.  For this reason, I’d suggest working with text in either Indesign or Illustrator.  Working in Photoshop will force you to use a higher resolution (200dpi-300 dpi) because of the text issue which will force you to render or use a larger image, negating the speed of using the smaller rendering or image.  See below for an example of the pixelated text and how the text needs to fit within a pixel as opposed to remaining vector based.

Text in Photoshop - click to see full size

4)  What is the output media going to be?  Print? Video? Billboard?

Typical video/computer/projectors use a 72 dpi standard.  HD video uses 1920 px X 1080 px (hence your tv is a 1080).  The computer monitor or projector will have their own resolution.  The laptop I’m writing this on for example is 1400 x  900 px.   As previously stated, printed material for hand outs should be min. 150 dpi and then printed presentation boards could go down to 100 dpi.  If you’re looking to create a billboard or rendering for site signage, you can get down to 50-25 dpi even.  I have even seen freeway billboard images that get down to 5 dpi and look fine from 100′ away.


5)  Think about what you are going to use the image for, both now and in the future.

If you need it at one size now, will you need it at a larger size for print/projection/etc later?  It’s always easier to reduce the file and reduce than it is to enlarge.  The reason for this is a bit technical but essentially, the algorithms that a program uses to “guess” what color a pixel needs to be when it’s enlarged struggle to execute effectively as they are asked to enlarge and compute more and more pixels.  Therefore if you’re asking Photoshop to increase an image 110%, it might do a decent job.  If you ask to increase that image 200% however, you’ll notice the image struggles to create accurate results.  Essentially, the enlargements that you see on NCIS, CSI, etc don’t really exist…sorry to burst your bubble!

Yes, there are ways that you can enlarge an image in Photoshop using “Resample Image” selection but remember, this still is an algorithm calculating it’s best guess as to what the color of the image should be.

The software will guess what color goes in each red square based on the color and surrounding colors from the white squares.

Just remember that these algorithms can cause problems if you reduce and image just to enlarge it again.  See what I mean below as I take an image, reduce it and then enlarge it to it’s original size.  the problem is that when going from small to large, it looks blurry or more pixelated because the computer is guessing what the pixel color should be.

Original Image Size - click to see full size

File reduced to 520 pixels - click for full size

Reduced file enlarged again to 1040 px - click to see full size


Now when you are working about to create a rendering, it starts off by figuring out what size the rendering needs to be.  For example, let’s say I need a rendering for a hand out.  This tells me that I’ll need at minimum 150dpi.  Go back to our pixel equation from above and we can calculate that our output should be 1650 pixels (150 dpi X 11 inches) by 2550 pixels (150 dpi X 17 inches).  What this also tells me is that with the same output or image, I can crop the image to fit my 1400×900 pixel laptop screen.

You don’t want to create an output too much larger than necessary because time is always going to be an issue.  Remember doubling the output isn’t actually doubling it.  A 11×17 image at 300dpi is actually 4 times (twice the pixels in height times twice the pixels in width)  the pixels as an 11×17 image at 150 dpi.  This means that it will take 4 times longer to render the 300 dpi image than the 150 dpi image!

White square = 1 px @ 150 dpi, Red Square = 1 px @ 300dpi

Again, because it’s easier to reduce rather than enlarge, I can reduce that same image to 8.5×11 easier than enlarge it to 18×24.  However, if I needed that image on a board that would be seen from 5-10 feet away, I know I can get away with about 100dpi which would allow me to enlarge the image to 16.5 inches (1650 pixels/100dpi) by 25.5 inches (2550 pixels/100dpi).

You can now understand how with a decent knowledge of this information a lot of time can be saved without reducing the quality of the image.  I know this was a bit off topic, but hope it helped.