Camera depth of field VS Photoshop Blurring.


Camera depth of field VS Photoshop Blurring.

Photoshop is masterful at mimicking photographic effects, plus all the add-on actions and filter sets do some impressive things. So much so that some new photographers start to feel if they get the image on the card, they can make any effect in the computer.

We see so much of the Photoshop effects we sometimes see it as the norm. Yet when you see a lens doing its designed for thing, it will take your breath away.

The lens depth of field, most noticeable in the shallow depth of field, has characteristics that imaging programs can’t quite replicate all the time. Using it will make you stand out from the crowd as they say.

To get the full effect of the camera depth of field, set your camera to its lowest F-stop. While a F1.4 and F2.8 are the most striking, F4 and F5.6 will work too, just not as strongly. Set your focus to its minimum focal length. That is the shortest distance the lens can be to an object or subject while still remaining in focus.

Move in on your subject until the critical element is in focus. You should instantly see the effect. You will see the background turn into blurred and blooming elements. The focus rapidly falls away.

It happens more to the background of course but the same effect works in reverse, forward of the subject. Here the effect is stronger the closer you get to the focus point, the more the planes of focus come into focus. The effect is most pronounced in macro lenses and long focal length lenses, which come with the bonus of compressing the background forward.

That is why if photographing a face you need to be careful of nose placement since it can be an inch or more out from the eyes, making it a large distracting element.

You can see the effect of the depth of field control in this image with the boat tie-off rings on a dock I took in Paris.


If there is a broad horizon behind your subject you won’t see too much of a difference. The Photoshop user has to apply one level of blur to the nearby subject then a different blur to the far subjects.

The challenge to the effect is how each device, the lens and the software, see the background. The lens sees it all as a multi-planed element. Every inch is slightly blurrier than the previous. If there are objects between the subject and the far horizon, in irregular distances and shapes, each will be blurred differently. The lens does not see the distance between the focused part of the subject and the far focusable point as one plane.

Which is how Photoshop and all imaging programs, see it. For these programs the surface is just one plane, a flat surface. If you are making a simple subject pop off of a background on one plane, like a wall 10 feet behind the subject, then a pretty seamless result will happen.

When those pesky in-between objects exist it gets challenging. This is especially true if the object has some front to back distance as well. Your mind knows that it cannot be equally in focus front to back, that a gradation of focus needs to exist.

So the image editor has to figure out what the blur amount would be for each object in the distance. Mask it. Blur it.

Lots of objects, lots of work, lots of room for error.

Then you get into the other out-of-focus effects a lens delivers. The natural Brokah effect that reacts to bright out of focus objects turning them into the aperture shape of the lens. The effect varies with the distance away from the focus point, the size of the out of focus bright points combined with brightness and color of the whole scene.


These are challenges for the software because again, it only sees the image as a single plane.

The effect works in reverse. Getting the distance subjects in focus too. You might have noticed the infinity symbol on your lens. This works at keeping everything, from the focus point to infinity, in focus. It works best or most effectively when you are at smaller apertures, which is the larger aperture numbers, like F-16, F-22 and even F-32.

The lens has the advantage because it is working in a dimensional space.

Software works its magic by affecting the contrast around the elements in the image. It tries to give the appearance of being sharp with that manipulation. It does not really sharpen anything. The more out-of-focus the receding planes are in the image, the more challenging it is for the software.

Mastering these physics of your lens will enable you to get your creative intent done in camera. It will stand out from the software creations becoming a more powerful image. Which is always the goal; powerful, storytelling images.

The bonus is, it is way quicker to do it in lens that it is in the software.


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