In Camera Sharpening

I recently came across an article that suggested that in-camera sharpening was better because it sharpened the image before it saved it as a JPEG, giving a better result than sharpening the saved JPEG later in Photoshop. I did a bit more research and couldn’t find a clear answer. So, I downloaded a lens test sheet, got out my faithful 40D and looked for myself.

What is Sharpening?

Before I dive into the test results, let’s clarify what is meant by sharpening

Sharpness is a much sought after characteristic of good photos. In the days of film it was easy – use a good lens, get your focus spot on, blow up the image and look at edges in the photo.If the edges look so clear that they could have been cut with a knife, the image was sharp.

Digital makes it more difficult. Because the pixels are arranged in a regular grid you can get interference patterns when photographing anything with regular, repetitive and closely spaced elements, like a mesh screen. These patterns, or moiré, are like the patterns you see when two pieces of net curtain move over one another. To avoid this most digital cameras have a low pass filter in front of the sensor that slightly blurs the image, which means that a photo straight out of a digital camera will never be quite as sharp as a picture shot on film.

The solution to this is to digitally process the image. A programme searches for edges and increases the contrast along them – it makes the dark edge darker and the light edge lighter – which reduces the fuzziness along the edges and makes the picture noticeably sharper.If this is overdone it creates halos around the edges a visible lighter and darker band running alongside each edge.

In cameras these settings are under the picture style menu. In some of the earlier Canon cameras the settings are called parameters. On most Nikons you will find the settings under the picture control menu. Other cameras? You will have to read the dreaded manual and, if you find it, please tell everyone on the comments below.

In or Out?

Now, back to the topic. This sharpening can be done in the camera, when the the camera processes the raw image to convert it into a JPEG, or afterwards on the computer. Most cameras have a standard setting that sharpens the picture because they assume that most people won’t be processing their images afterwards. On the other hand, the majority of professionals switch it off, preferring the additional control in post production editing.

For the test I set up an ISO test sheet on the wall, got out the 40D (Canon of course), mounted my new 85mm prime at f 8, for sharpest quality, and shot a series of pics, first with no sharpening and then with the camera set to 1, 2, 3, 4, 5 and 6 (Canon’s default setting uses sharpening set to 4). I then enlarged the JPEGs on PS and started scratching my head.

When I enlarged the pics to a 100% crop, there is a definite difference between no sharpening and the S1 setting and a steady improvement from S1 to S4, though S5 and S6 started looking a bit over the top.

The photos are below – see for yourself. If you click on the small picture you can see a bigger version with the detail

When I enlarged the images to 300% the differences became more pronounced. S0 was noticeably blurry, S1 and S2 better, but from S3 there was obvious fringing along the edges. This is a no-no for post production – any localised sharpening will show up

In any post production, there will always be a bit of sharpening, either on a section or across the whole image. To check the effect of the different levels of in camera sharpening on sharpening in Photoshop, I found the first bit of useful

information. I used the default Photoshop setting for unsharp mask – 100%, 1 pixel radius and a threshold of 0. When I applied this setting to the pics taken on the S1 and S2 settings it gave nice clear images with a minimum of fringing and nice smooth edges. These were especially noticeable around the figure 8. As expected, the S3 and S4 camera settings showed noticeable fringing as well as unpleasant jagged outlines on rounded edges.

Working on the picture without any in-camera sharpening, I had to use far stronger unsharp settings to get similar sharpness – 150% and 3 pixels radius. While there was less fringing than the S1 and S2 pics, the edges were much smoother.

Conclusion

So what does this all mean? On one level, not much. The effects of the settings were only evident at 300% enlargement. At 100% the no sharpening setting was, as expected, softer. The S1-S4 in-camera sharpening settings were noticeably better and all four looked quite acceptable.

If you are passionate about your image quality then you need to experiment with some of the lower sharpening settings in YOUR camera. Setting it to S1 or 2 and then using mild unsharp mask settings may give you smoother edge definition with little or no noticeable fringing. If your camera is set to the standard mode with the default sharpening setting of 4, then you probably should dial it down to 1 or 2.

As always, PLEASE try this at home.

Different makes and models of cameras will use different sharpening algorithms so you may not get exactly the same result. It seems worth the effort and I am going to try it out over the next few days – watch this space for more comments


A last word – not significant but interesting. As I took the pics, each using a bit more sharpening, the file size grew a bit with each increase in sharpening. Same image, same exposure, same everything except sharpening.