Here is a trick I discovered in Photoshop to bring out the details in photos or other drawings.

The general idea is that any effect in photoshop - surface blurs, contrast changes, tone changes, etc - can be inverted to give the opposite effect. Surface blur is great for removing details while preserving hard edges. Now you can use it to bring out those details and not have halos glowing around those edges.

1) (Top left image) this is the original image. We want to bring out the details of this.
2) (Top center) Using a unsharp mask filter does bring out the details but it causes halos. Look around the corners of his uniform.

Instead, we have to try something different. We don't have any sharpening tools that do what we want, but we do have a blur tool. What use would a blur tool have? We can apply it, but then transform the results to get it to do the exact opposite - sharpen the image.

3) I duplicated the image in a new layer. Then I applied "Surface Blur" and adjusted the knobs so that the details I want to bring out are, instead, blurred out.

Next, to transform the resulting blurry image into doing the opposite of what it just did.

4) I inverted the blurry layer. Then I duplicated the original. I blended the blurry inverted layer with the duplicate using Linear Light at 50%.

This causes only the differences between the original and the altered (blurry) image to remain, while the others filter out.

5) The result. I combined the two layers leaving this greyish one and the original. This greyish image contains only the details we removed using Surface Blur.

Now we'll bring those details back in.

6) Blend the greyish image with the original. Use Linear Light with 100% opacity. Adjust the opacity to change the amount the details are enhanced. Merge the two layers if needed.

Now, you'll see that the details which are hard to see are sharpened, while the already clear edges don't produce halos - unlike the traditional unsharp mask.

Last two images - Using this technique on a larger scale it is possible to enhance contrast in an image, creating an HDR effect. The first image (Bottom Left) is without any modifications. The second image has the technique applied. I also used the same technique to enhance finer details.

This inversion technique will apply to almost any filter. Filters that won't work with this technique include distortions, artistic effects, and noise adding filters.

The source images used JPEG compression. Be careful, since JPEG artifacts will be emphasized using this method.