Control Your Sharpening Halos, Sharpening Photos for Submission to Istock

(Note: This tutorial is aimed at istock photographers wanting to sharpen their photos before submitting them to the istockphoto inspection process. This tutorial’s usefulness is not limited to microstock photographers. The technique of sharpening described below works well for most images. If you are using this method of sharpening on your non-microstock/non-istock photos, remember, that you can use higher sharpening settings than those I recommend in this tutorial. I normally sharpen my photos to suit the size they will be displayed. Istock inspectors view submissions at 100% size (one pixel of the photo is one pixel on the screen) so I do all my sharpening for istock at 100% size (ctrl+alt+Zero). The photos I display on this blog are normally only 870 pixels wide. When I sharpen photos for the blog I view them at 870 pixels. The same goes for printed photos – view them at their printed size when sharpening them. You can get away with a lot more sharpening with a view that is smaller than 100%).

I’m pretty sure istockphoto doesn’t want its photographers to submit sharpened photos. In fact, I think somewhere in their submission guidelines it states that you should not sharpen your photos. But, how many times have you gotten a rejection for “no clear center of focus” or something like that? The problem is istock inspects photos at 100% size, and the nature of digital capture results in a slightly soft image before sharpening is applied. This softness is especially noticeable when viewing photos at 100% size – the way istock inspectors do. Even if you use the best lens and a stable tripod a digital photo that hasn’t been sharpened will look slightly soft when viewed at 100%. How do you escape this Catch 22 (your photos are slightly soft, but you are not allowed to sharpen)? The answer is: CHEAT! Istock is setting absurd expectations for its photographers. You have no other choice than to sharpen. I sharpen all my istock submissions, and my acceptance rate is around 78%. My acceptance rate would be even higher, but I submit a lot of experimental, envelope pushing stuff that often times gets rejected. I haven’t been rejected for sharpening yet.

If you are going to cheat, and you want to get away with it, you must be sneaky and subtle with your sharpening. That’s what this tutorial is about – how to slip some sharpness into your photos without getting noticed. To achieve this level of subtlety you need total control over your sharpening halos. We’re going to do the sharpening on two layers. One layer will control the dark sharpening halos and the other will control the light halos.

“Wait, what’s a sharpening halo?” you might ask. The photoshop unsharp mask filter creates small halos along edges to increase the appearance of sharpness. On the dark side of an edge USM (unsharp mask filter) makes a dark halo area, and on the light side of an edge it makes a lighter halo. Below is a basic example. Imagine the line dividing the light gray area from the darker gray is an edge in your photo (by “edge” I mean anything that defines a shape — like the edge of a leaf, a window frame, a person’s eye lash. You get it, right?).

Below is the same image with USM (unsharp mask) applied. I used crazy huge settings so you can better see the effects. Notice the dark, almost black halo on the dark side, and the light, almost white halos on the light side. Similar but less obvious halos are produced when you apply USM to your photos. When a photo is sharpened the correct amount for its size the halos are too small to see and create the illusion of sharpness. However, if you make the halos too strong, or view the image at a large size, the halos become visible and no longer create the sharpness illusion. Big, strong sharpening halos look like garish artifacts.

For the purpose of getting through the istock inspection process, I have found that the light side halo shows up as an artifact a lot sooner than the dark side of the halo. Nothing gets an inspector’s attention like a bright, blown out sharpening halo. Wouldn’t it be nice if we could somehow run the USM filter and create only dark halos, or better yet be able to control the strength of the light and dark halos separately. A perfect combination for me would be a strong dark halo and a faint light halo.

Fortunately, there is a way to split your halos and attain total halo control. The next few steps are a little bit magic so pay close attention. I’ll use the original dark gray on light gray edge example from above to illustrate the steps required to split your sharpening halos into two controllable layers

Step 1: Start out by duplicating the Background layer (ctrl+J).  Every time I sharpen an image I do the sharpening on a duplicate layer. That way I can delete the layer if I screw up or I can lessen the sharpening effect by decreasing the layer’s opacity.

Step 2: Apply the Unsharp Mask filter to the duplicated layer. Choosing USM settings is beyond the scope of this tutorial. Choose whatever works for you. For istock, my standard settings are Amount 135 Radius .8 Threshold: 2. These settings work on most photos, but you’ll probably want to do a bit more research on the USM dialogue box, or maybe one day in the distant future I’ll write another tutorial explaining it all. So you can see what’s going on I am using ridiculously high settings for this example.

Step 3: Create a copy of the sharpened layer (ctrl+J). Now, you should have two sharpened layers and one not sharpened background layer. Your layers pallet should look something like the example below.

Step 4: Click on the lower sharpened layer and change its blending mode to darker color. The darker color blending mode means this sharpened layer will only show where it is darker than the layer below it.  Check out the example below if you are not sure how to change layer blending modes.

Step 5: Click on the upper sharpened layer and change its blending mode to lighter color. The lighter color blending mode means that this sharpened layer will only show where it is lighter than the layer below it.

Do you see where this is all going? The lower sharpened layer now only shows up where it is darker than the original, and the upper sharpened layer only shows up where it is lighter than the original. Because of the blending mode the lower layer now is in effect only the dark halo, and the upper sharpened layer is only the light halo. By lowering the opacity setting on either layer you can control the intensity of its halo. For example, if you reduced the upper layer’s opacity to zero, the light side halo would completely disappear. Or, you could do the opposite and lower the opacity of the lower layer to decrease the presence of the dark halo. Isn’t that slick? You now have separate control over the dark and light halos.

Here is the example illustrated. The upper layer’s opacity has been set zero. The brighter halo completely disappears.

You can do the same thing to the darker halo by sliding the lower sharpened layer’s opacity to zero. In the example below the lower (darker color) layer’s opacity is zero and the upper lighter color layer’s opacity is 100%. Notice that the dark halo isn’t visible, but the light halo is.

By now your wheels should be turning. What is we wanted a faint light halo, and a fully dark halo? The answer is simple. Leave the lower layers opacity at 100% and dial back the upper layer’s opacity until the light halo’s sufficiently faint for you.

You now have total control over your sharpening halos.  When editing your photos for istock I recommend zooming in to 100% size and scrolling around your image to see the effects of sharpening the way the istock inspector will.  Adjust the opacity of the two layers to reach a desirable amount of sharpening.  Remember, you want your image to look sharp, but not sharpened.    Pay close attention to bright areas of your photo.  Lots of times the USM filter will take a bright spot and drive it to completely blown out.  If you notice this effect simply reduce the opacity of the light halo layer until you bring the bright spots down to an acceptable range.  Usually the more noticeable artifacts are created by the light halo, but it doesn’t hurt to also play around with the dark halo layer opacity.  I always try to dial the opacity of both layers back as far as possible to keep the sharpening hidden from the inspector.

Step 6: Once you have are satisfied with the level of sharpening it’s time to flatten the image.  Right click on the bottom layer and select flatten image.

That’s all there is to it.  This process is slightly more complicated and time consuming than standard sharpening, but I think the extra effort is worth it.  Let me know how it works for you.  Also, would you like to see  this process shown on an actual photo instead of a gray scale example?  I am thinking of writing a part two to this tutorial using an actual photo that I submit to istock.