Beginner What Does Diffraction Look Like?

[Forkbeard]

How can you tell the difference between camera shake or slight movement and diffraction? I took some shots today (same subject/focus point) and from about f10 onwards they deteriorate in sharpness, but I can't tell if it's down to slight movement of the tripod or this thing called diffraction! Obviously the ones at a smaller aperture are longer exposed and more prone to shake. VR was off while the camera was on the tripod.

Also, does the amount of diffraction change between lenses or is it dependent on the sensor or something?

 

[Nawty]

Post up some samples and we can see although given you were on a tripod it could well be diffraction which appears as a general softness to the image. Things like image slap show tell-tale signs of directional blur.

 

[Forkbeard]

OK, the focus point on all three according to ViewNX2 is the stalk of the plant (which it should be):

f32



f8



f11

 

[Nawty]

Looks like diffraction to me!

 

[pingu666]

the smaller denser sensors hit diffraction earlier, i think for 24mp crop its around f7.1 to f8 but slightly past that should be ok or easily recoverable in post

 

[James Wheeler]

This site has a cool explanation and a tool for visualising your airy disk for your camera vs pixels at various aperture settings - this helps in showing where your diffraction limited aperture is

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

 

[Forkbeard]

So how do people get decent macro shots at really high f numbers, or does diffraction not work the same at close quarters?

 

[Forkbeard]

This site has a cool explanation and a tool for visualising your airy disk for your camera vs pixels at various aperture settings - this helps in showing where your diffraction limited aperture is

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

Thanks, that has cleared it up for me.

 

[TimmyG]

So how do people get decent macro shots at really high f numbers, or does diffraction not work the same at close quarters?

Sometimes you can get away with it, if you are displaying at small size on the web for example, some images can still look quite sharp despite the effects of diffraction. Other than that you need to look at focus stacking. You basically shoot a series of shots at lower aperture to retain detail, but at different focal planes. You then combine these in post processing to give you the necessary depth of field.

Here's an example of diffraction occurring at high aperture compared to low aperture, but not the difference in DoF also:

Indian Meal Moth - Aperture comparrison by Tim.Garlick, on Flickr

And here's the stacked image, 11 individual frames combined to get the full subject in focus (although not one of my best I don't think...):

Indian Meal Moth by Tim.Garlick, on Flickr

 

[Forkbeard]

Ah right. Nice picture TimmyG.