As the holidays approach, I find myself editing a lot of pictures. A question came to mind the other day while I was working; one that I had wondered a couple of years ago – what are the differences between all of these Photoshop blur filters and how do I decide which filter to use?
I use blurs to simulate depth of field, smooth skin tones, and add focus to a certain part of an image. I know of people who use blurs for many more things, such as special effects and to blur edge pixels to mask bad cuts (though this is best done with the blur tool). The questions still remain: how do I decide between gaussian blur and lens blur, what’s a shape blur, what’s the difference between smart blur and surface blur, and just what the heck is “average” blur?
We’ve done our homework and are going to answer these questions for you. We won’t go into a ton of technical detail (just the basics), but we will tell you a little about each blur and how it works, how each blur is intended to be used and we’ll touch on other applications for each blur. As always there are plenty of images for comparison and there are several written and video tutorials explaining the blur types as you work your way down the page. Be sure to scroll to the bottom to see our downloadable blur comparison image.
Video Tutorial – Part 1:
Blur filters can be found under Photoshop’s Filters menu. The first type of blur you will find when you get there is “average.” There are many people who don’t know what average is and, to be honest, I rarely use it – with one exception. So what is average?
Average simply takes a look at everything in your layer – or everything you have selected – and averages the colors together. The filter is intended to give you one uniform color to smooth things out. This is great for 2 different things: the first is for removing texture or noise from a photograph or selection. There is a great video online already, for doing just that, so I’m not going to repeat the tutorial. Click here to see Ian Barber’s tutorial on removing texture.
A great technique that uses the average blur, that I do use fairly often, is this: removing color casts from images. Normally, we’d do this with a curves adjustment or maybe with a color balance adjustment layer. This average blur method is quick and easy. It works best on images that have a large amount of white areas and works beacause the blur filter averages the colors to the average hue of the color cast. Here’s how to do it:
Removing Color Casts with Average Blur:
Step 1: Duplicate your original image to a new layer.
Step 2: Apply the average blur filter to the duplicated layer.
Step 3: Add a Levels adjustment layer on top of the other layers.
– To do this, click on the half-white/half-black circle in the layers pallet and select Levels.
Step 4: Click on the grey point sampler.
– This will sample the average hue of the color cast and adjust the colors so that this becomes a neutral grey.
Step 5: Turn off (or delete) the duplicated layer.
– We don’t need it anymore. The adjustment is being made by theLevels adjustment.
Cool right? If you know of any other good uses for this filter, please comment below!
Blur & Blur More
I’m lumping these 2 together because they are the same thing! I have seen and gone through a lot of tutorials on the web that utilize these filters, but I pretty much NEVER find myself using them. They are kind of like Photoshop’s version of “auto blur.” You have no control over the amount applied, the radius or anything. When you apply blur, Photoshop looks for pixels with a “significant color transitions” (Adobe Help Files), and applies blur to these areas.
The big use for these filters is to smooth edges. In my everyday use, I find the transitions to be so subtle that I can’t even tell they are applied – in MOST cases. Though it may seem obvious, I should state that blur more does the exact same thing as blur, but it applies it more aggressively. According the the Adobe Help Files, blur more is three or four times stronger than blur.
Box blur is a pretty cool blur, but it is a non-realistic blur. Therefore, it is best reserved for special effects, in my opinion, unless you are specifically going for that non-realistic look (in which case, go for it).
Basically, this is how it works: Photoshop looks at a pixel, then compares it to the pixels around it (hence the “box” term) and then averages these colors together to create a blur effect. When you apply this effect, you can specify the radius, which tells Photoshop how far away to go (how many pixels to include) when averaging these colors (i.e. how big the “box” is). This is why the blur is spread farther when your radius is set larger.
The workhorse of the blur filters, Gaussian blur has many practical uses. Why do I capitalize the “G” in Gaussian? Because it is named after mathemetician and father of the Gaussian lens formula and system, Carl Gauss. The Gaussian is named such because it is based on a Gaussian function (see this page is you want to know more technical details of Gaussian functions).
To be less technical, Gaussian blur applies a much smoother blur than that of the box blur, and because of this, it is often used to smoothing detail in an image; particularly in skin tones. It can be used to add a soft focus effect to an image too. Let’s take a look at a typical scenario to soften an image, while retaining sharpness:
Smoothing an image/removing noise, while retaining sharpness with Gaussian blur:
Step 1: Duplicate your layer.
– If your image has been edited and is in multiple layers, you should first merge your layers to a new layer (I like to use
Cmd+Alt+Shift+E to merge to a new layer, while still keeping the old layers. Then, I stick my old layers in a group).
– Duplicate this merged layer.
Step 2: Apply a slight Gaussian blur.
– The amount will depend on the resolution of your image. You should start to notice a smoothing of the image, but you
don’t want to lose detail on the edges. In my example my radius was 1.2.
– It helps to zoom in tight on something, preferably skin tones, if people are your subjects.
Step 3: Duplicate the original (or the merged) layer and move it to the top.
Step 4: Apply a high pass filter to this new top layer.
– This is found under the filters menu in the other category.
– Set the radius to the point where you can just see the edges. The smoother points should not show through too much.
Step 5: Change the blending mode of the top layer (the high pass layer) to overlay.
– You may want to reduce the opacity of this layer too. That’s up to you!
The other thing that I typically use Gaussian blur for is to add focus to an image. I simply create an elliptical marquis around the subject that I want to be the center of attention (on a new layer), feather it, use the selection to punch a layer mask in the top layer, and blur the lower layer, which is the area that was outside of the marquis selection. Please see the accompanying videos for a more in-depth tutorial on this. Here is a before and after shot, though ( I went a little extreme with this so you could see the results on your monitor):
One more thing you should know about Gaussian blur: It is a “low-pass” filter. This means that it will effect the high frequency colors first (violet, indigo, blue, etc…). Since white is all colors combined and black is the absence of color, white is a higher frequency, and therefore is effected first. This can give the image a hazy look.
Video Tutorial – Part 2:
Lens blur is an attempt to mimic the blur you would get from a real lens. It is a very powerful filter, compared to some of the others, and sometimes seems to get overlooked. With it you can simulate depth of field and even create a bokeh effect by specifying the size and shape of your iris opening. Many tutorials online use Gaussian blur when dealing with creating depth of field. This method is okay (in fact I used to do it), but it is not optimal. Lens blur is much more realistic. Here are two tutorials which show you how to achieve the to effects we just discussed, using lens blur:
Simulating Depth of Field with Lens Blur:
*There are a couple of ways that you can go about setting up your Depth Map. This is the method is only one of those, and is the method I use the most. If you find another method more convenient for you, then by all means, use that method.
Step 1: Duplicate your background layer.
Step 2: Add a layer mask to the top image by clicking on the “add vector mask” icon in the layers pallet.
Step 3: Create a gradient by dragging from the top to bottom.
– Start dragging at the point that you want to start becoming in focus.
– End at the first point that you want to be completely in focus.
– It may help to turn off the lower layer temporarily, so that you can see what you are dealing with.
Step 4: Make sure that mode is set to “difference” in the options panel for the gradient, and add a bottom to your gradient.
– Again, drag from the top toward the bottom of the image, starting this time at the point that you want to be completely in focus, and ending that the point that you want to be completely out of focus.
– If your subject is close enough to the camera, you may not need another point. Simply skip this step. However, you will need to click “invert” in the options for step 5.
Step 5: Add the lens blur filter.
– Be sure to click on the image icon for the top layer first (if you don’t, you will end up applying the blur to the gradient mask).
– Select Filter–>Blur–>Lens Blur
Step 6: Set your depth map by selecting “Layer Mask” as the source.
– Set all parameters accordingly. Please see below for a list of the parameters and their descriptions.
Step 7: Apply the blur by clicking “OK” and save your image – you’re done!
Simulating the Bokeh Effect with Lens Blur:
Step 1: Duplicate your background layer.
– You may wish to apply a gradient, if you are going to add some depth of field blur. If so, please see the above tutorial (steps 2-6).
Step 2: Add the lens blur filter & set parameters accordingly.
– Select Filter–>Blur–>Lens Blur
– See below for a list of parameters and their descriptions.
Step 3: Set up the Specular Highlights section.
– I like to start with brightness at 100.
– Be sure the Threshold is set to 255 (all the way up) and then slowly start to bring it down until you are getting the bokeh look in the right areas.
– Lower the brightness slider, if you like.
Step 4: Apply the blur by clicking “OK” and save your image – you’re done! Here’s a before and after:
Overview of Lens Blur Parameters:
You maybe a little overwhelmed at all of those parameters in the lens blur dialog. They are not as daunting as they may seem, though. Here is a brief description of what each parameter does, but please check out the accompanying video, where I describe the parameters and demonstrate each one.
Preview & Faster/More Accurate:
Updates the image in the preview screen to show you the original image, or the image with the blur applied.
Faster & more accurate control how accurately the preview window displays the blur, but will not affect the final application of the blur. Faster will allow your computer to process the blur more quickly, which is where I tend to leave this set.
–Source: This tells the filter what to use to determine which areas of the image to leave untouched and which areas to blur. I tend to use “layer mask.” With layer mask, areas of the of the mask that are white are blurred, while areas that are black are left untouched (depending on how you set up the next two parameters.
–Focal Distance: This determines which value of grey is considered completely in focus. 0 is completely black, while 255 is completely white. I set my focal distance to 0, meaning that pure black is completely in focus. Everything that is lighter than pure black will gradually become more and more out of focus, leaving pure white (255) completely out of focus (if you drag your slider all the way to 255, then pure white will be completely in focus, while pure black will be completey out of focus). Then, I adjust my slider slightly to alter the the depth of field.
Alternately, what I really like to do is just click in the image at the point that I want to remain completely in focus. This will set the slider automatically to the correct point. Then, you can just make some fine-tune adjustments. *Note that setting your slider to, say, 50 means that the grey-scale color with the value 50 will be completely in focus, while anything below 50 (closer to black) and anything above 50 (closer to white) will gradually become more and more out of focus. This is why I tend to use a double-gradient and just let black be completely in focus. This way, I am in precise control over which area is completely in focus.
–Inverts: This just reverses the grey scale value that is considered in focus. 0 becomes 255 and visa versa.
–Shape: This is the shape of the iris. Important not matter what. but especially important if you are simulating the bokeh effect. Default, I believe, is Hexagon (6 blades). This will directly effect the shape of your bokeh. The higher the number of blades, the more rounded your bokeh will become.
–Radius: This simulates the opening of your iris. Basically, this is your aperture, but it is not displayed in f-stops. Choose a value from 0-100. The higher the value, the more intense your blur will be (a larger aperture=shallower depth of field=more out of focus). Use this in correlation with Focal Distance to achieve a realistic depth of field.
–Blade Curvature: Determines how much the “blades” of the iris overlap each other. I higher value will achieve a more rounded bokeh.
–Rotation: Literally rotates the shape of the bokeh (rotates the blades of the iris). This is more obvious when creating bokeh and using a less-rounded shape.
This section is where you will set up your bokeh. Areas that are naturally bright in an image (like lights), or even white objects, will tend to become greyed out as you apply blur. This happens because these pixels are being averaged with pixels around the object (which are not white) to create the blur, thereby darkening the whites. This area is where we correct this issue.
Brightness: Brightens these areas. I tend to start with the brightness at 100 while I adjust the threshold and then lower the brightness once I’ve found the desired threshold.
Threshold:This determines which pixels are being affected by the brightness slider. At 255, only pure white pixels are being brightened. You may not notice much of a difference. As you begin to lower this value, darker pixels will also be affected. Try lowering it to 0 (meaning everything that is pure black or brighter will be affected). You should end up with a bright white image. A lot of times, you only need to lower this a smidge (is that a word?). I find myself setting it at 254 all the time.
The last section allows you to add noise (i.e.-film grain) back into an image that may have been lost during the bluring process. You may not need a lot.
Amount: How much noise to add in (many times, you will only need a value or 2 or 3).
Distribution: Gaussian or Uniform (how the noise is applied to the image).
Monochromatic: Apply noise to all pixels, or just the grayscale pixels.
Motion blur mimics the look you would get if you were to either move the camera while shooting, or snap a shot of a moving subject (at a relatively low shutter speed). You can set the angle and the distance of the blur. If you would like to apply the blur at multiple angles, just apply it two times. Here’s a quick tutorial on implying motion blur from a moving subject:
Implying motion blur with the motion blur filter:
Step 1: Duplicate your original layer.
Step 2: On the top layer, select your subject using your favorite method. I like to use the quick select tool.
– In this case, it is not important that your selection be perfect, since we are going to be blurring the subject. In fact, in this example, I didn’t even have the right arm selected!
Step 3: Copy the selection and Paste it into a new layer.
– Command+C to copy and Command+V to paste.
Step 4: Duplicate this layer (this is optional, but I like to do it…you’ll see why in a second).
Step 5: Apply the motion blur to the top layer.
– Set the angle to look like the blur is coming from the direction that the movement came from.
– Set the direction fairly high, depending on the look you are going for.
Step 6: Move the layer.
– Select the move tool (V) and offset the layer so that the blur creates a trail from the moving subject.
Step 7 (optional): Duplicate.
– If you would like the effect to be stronger, duplicate this layer and leave it in place.
– If you would like the trail to be longer, duplicate the layer and move the new layer further down the trail.
Step 8 (optional): Overlay the original to cover up motion.
– In many cases, you may want the blur to overlap the original image. In some cases you don’t. If you don’t want it to, simply move the original copied layer (the one we made of the selection) to the top of the layers pallet to cover up the blur over the subject.
Radial blur mimics the look that you would get if your were to either rotate the camera while exposing the image, or if you were to zoom the lens while exposing the image. Simply apply the filter and select Zoom or Blur and move the center of the blur by dragging the plus sign around in the “Blur Center” box. You may also choose the quality of your blur: draft, good or best.
To me, this is the most useless of them all, thought I’m sure there are those out there with a need for it. This filter applies a blur by blurring pixels within a selected shape (called a kernel). Use a predetermined shape or use your own shape. In the example below, I’ve used the copyright symbol and I’ve set my radius at 121 (fairly low), to be able to make out the shape. A good candidate for special effects, I suppose.
This is a filter that I rarely use, but has it’s uses. Smart blur blurs an image “with precision,” according to Adobe’s help files. Basically, this is best for reducing grain in an image, without affecting image detail. I haven’t dealt a ton with grainy images, which is why I haven’t used this filter much. However, those that do use it, I’ve read nothing but praise from. Specify the radius (the area to search for dissimilar pixels), the thershold (how different pixels must be before they are blurred) and the blur quality. You may also choose a mode: normal (affects the entire image), edges only (affects only the edges – where pixels change value) or edge overlay (affects the edges only and overlays them on the original image).
One of my favorite filters, surface blur smooths pixels that are different, but tries to leave drastic changes (edges) in-tact. Because of this, it works well for reducing noise, but also it’s also great for retouching skin/removing wrinkles. If you would like to get in to retouching photos, you will probably want to experiment with this filter. Be advised that you can very easily go too far. If you were to retouch for a fashion or beauty magazine, it’s very likely that you’d want to go a bit overboard, as they often do. But if you are a family photographer or if you are retouching your own family photos, then you’ll want to set the layer opacity down a bit to tame the effect.
The radius determines the distance to blur from the original pixel and the threshold determines how different pixels must be before they are affected. Setting the threshold too high will result in edges being affected. Here’s a quick tutorial:
Smoothing skin with Surface Blur:
Step 1: Duplicate the original layer.
Step 2: Apply the surface blur.
– Filter–>Blur–>Surface Blur.
Step 3: Set the parameters.
– I set mine at 71 for the radius and 20 for the threshold, to be a bit extreme.
– Apply the filter by clicking “OK.”
Step 4: Create a layer mask and invert it.
– We only want to affect the skin in this image, so create a mask on the layer by clicking the “vector mask” icon in the layers pallet.
– Invert the mask by pressing Command+I on the keyboard.
Step 5: Using a soft brush, paint over the areas that you want to be blurred (the skin) with white.
– Press “B” to select the brush tool.
– Use the left and right brackets, seen here: [ ] to adjust the size of the brush as you paint.
– If you make a mistake, either undo, or paint back over this area in black.
Step 6: Lower the layer opacity.
– Like I said above, unless you are editing for a major magazine, you will probably want to tone down the blur quite a bit. I am a fan of going a little overboard with the filters and then backing it off with the layer opacity. This really helps me to dial in the exact look that I’m going for.
– In this example, I’ve set my opacity to about 60.
Comparing the Filters:
I’ve always thought it would be helpful to have a chart comparing the different blur filters, but haven’t been able to find one out there. Below is a chart that is just that! Feel free to copy, save or print this for your reference. Download the full quality image by first clicking on the image to open the HQ version, then just right click (Ctrl+click for mac) and “save image as.”
This wraps up our overview of the Photoshop blur filters. I hope that you have found this helpful. As always, pleas leave comments and suggestions below! And new with this lesson, feel free to Pin us on Pinterest. The videos or the comparison chart above make great pins! Thanks for reading!