Optimum DSLR Aperture Range?

B

benlen

Member
Greetings folks,

This is an issue I've had shooting with DSLRS that I'd love to have clarified!

When I shoot with a DSLR at a shallow depth of field (wide open) and focus on a specific object within my field of view, my focus/sharpness is often quite good. For some extreme bokeh, I've gone down to as low as 1.8 (using an ND filter to isolate nature objects). The shots turn out great. The part of the frame I want in focus is in focus, and the rest is pleasantly blurred.

However, when I want to have a shot where just about everything is in focus, I run into some issues.

First, there's the question of how high a aperture I should shoot for! I read early on in my DSLR shooting days that going beyond 11, to something like 16 or 22, actually defeats the purpose of wanting everything in focus because diffraction and vignetting is the result.

So here's a scenario: I'm shooting video outdoors, a landscape (mountains, forests) and I want to keep things crisp but also have a wide depth of field...what is my go to aperture?

And what is a good aperture range for video from a DSLR?

Thanks a bunch!

-ben
 
Most lenses are at their best in the f/4-f/5.6 range. Beyond f/8 diffraction will become noticeable. But DSLR video is not very high resolution to begin with if you are looking for really crisp deep dof wide shots.
 
Is there a problem with the stills function of your DSLR?
Take a bunch of photos at different apertures and different focal lengths. Study them. Rinse, repeat.
 
CPC, that might give me a good idea, but I'm assuming there's a "best practice methodology" here that I'm not informed about.

I've found that on DSLRS (particularly Canons) the advice of comparing stills to video is not a solid one, as the compression on RAW images versus H.264 videos is quite different. For example, I shot a video in Central Park last fall and a picture at the same aperture (around f8, I believe) and the results were terrible in video, but great in still.
 
Razz16mm said:
Most lenses are at their best in the f/4-f/5.6 range. Beyond f/8 diffraction will become noticeable. But DSLR video is not very high resolution to begin with if you are looking for really crisp deep dof wide shots.
Click to expand...

Thanks Razz, this is solid info.
 
benlen said:
Thanks Razz, this is solid info.
Click to expand...

You sort of have two basic conflicting processes at work... on the one hand you want 'sharp', on the other hand, in order to avoid moire effects, you want an optical low pass filter which 'filters' out spatial frequencies, that is 'softens' the image, that would contribute to moire effects...

For most 'scenics', unless you have the need for something sharp in the extreme foreground, and likewise 'sharp' in the distance... find the lens' hyperfocal distance, for a given mm in length, for a given f-stop, that point will be 'out there' and relative to the desired Circle-of-Confusion, the image will be 'sharp'...

For example, my GH-1, with a 25mm lens, and an f-stop of 8, yields a hyperfocal distance of 17' 2". So if the subject is placed at that point of 'sharp' focus, from 8' 7" to Infinity, will be 'sharp'. Perhaps not 'critically' sharp, if you enlarge it pixel peep... but 'sharp' for the assumed viewing distance of the ultimate projected image.

If you want 'sharp near' and 'sharp far', without recourse to deep DoF... you need a split diopter lens. There will be some 'fuzz' where the split transitions from one curvature to the other... but that's the idea.

There is also a 'tilt' lens which allows on to change the angle of the lens, relative to the sensor image plane, which allows a 'shallower' DoF to 'look like it's near and infinity focus'... see View Camera techniques for a detailed description...
 
I quite like the deep focus cinematography of the 40s and 50s, and yes, it's much more difficult to get deep focus with a big sensor. Except you may need to show off your DR to set your footage apart from the video look.

The mathematical rule is as follows: if the crop factor between two systems is, say, 1.5x, on the smaller sensor you get the same FoV and DoF when you divide both your focal length and aperture by 1.5x. So, from 50mm f/2.8 to 35mm f/1.8. Full example here.

Now, about how narrow an aperture you're ready to use, it's best to test it with your camera and your lenses, but after reading this I kind of lost my fear of diffraction. It's there, but it's not nearly as bad as people think. I'll use f/16 or f/22 if I have to.
 
Samuel H said:
Now, about how narrow an aperture you're ready to use, it's best to test it with your camera and your lenses, but after reading this I kind of lost my fear of diffraction. It's there, but it's not nearly as bad as people think. I'll use f/16 or f/22 if I have to.
Click to expand...

What is really 'wyrd' to me is some people wax 'gushing' in using old lenses especially some Canon lenses, which they indicate gives their images a 'creamy' look, then, worry about diffraction...

I don't think I ever 'worried' about diffraction...
 
Razz16mm said:
Beyond f/8 diffraction will become noticeable.
Click to expand...

back up the misinformation train.

diffraction is not 'noticeable' in all circumstances above f/8.

The physical effect of diffraction may be beginning, but noticeable is entirely relative to the camera, the lens, the focus distance, the shot in all its aspects, etc... and to of course the viewer.

While i like to stay in the 5.6 range, If i need the DOF, i'll go as high as f/16. the effects of diffraction may be having an effect, but that's completely meaningless if the shot looks good given all the above stated circumstances.
 
Some cool links to check out...

The DOF Master website has a DOF calculator, where you can check to see that a 25mm lens at f/4.0 on a GH3 camera has the SAME DOF as a 50mm lens at f/8.0 on a Canon 5D camera.

DOF Master : Depth of Field Calculator


The Cambridge in Color website has a Diffraction Limit Calculator ( near the bottom of the page ), where you can plug-in the format of the camera you are shooting with and then test the different F-Stops to determine what's the smallest aperture that you can use without being diffraction limited. ( for Micro 4/3 and APS-C it's f/11 )

Cambridge in Colour : Diffraction Limit Calculator
 
Darren Levine said:
back up the misinformation train.

diffraction is not 'noticeable' in all circumstances above f/8.

The physical effect of diffraction may be beginning, but noticeable is entirely relative to the camera, the lens, the focus distance, the shot in all its aspects, etc... and to of course the viewer.

While i like to stay in the 5.6 range, If i need the DOF, i'll go as high as f/16. the effects of diffraction may be having an effect, but that's completely meaningless if the shot looks good given all the above stated circumstances.
Click to expand...

Agreed.

I can show you camera test results where on certain lenses you'd be hard pressed to see a difference between f5.6 and f8.

Had the same discussion with a "professional DP" with designations beside his name of course.

In general after f5.6 things do typically start to change but as for how drastic it will really depend on the actual lens itself.
 
Thank you everyone for your replies and discussions!

I'm new to the GH3, and love it so far––someone with a brain really designed this for video (minus the focus peaking, of course, but that's minor)...

I've currently only purchased one lens, a 14mm f2.5 pancake. I picked up this lens for its purported sharpness and light weight, which is essential for many backpacking video projects I do (out in the woods, I really don't want to be lugging heavy glass).

In a quick test, I didn't really notice a huge difference between 5.6 and 11 when it came to doing a shoot of a stand of trees across a small river. Only the farthest trees seemed slightly sharper at f 11.
 
Remember: the farther you focus the greater the dof. Focus on a closer tree and the sharpness/blurrinees of the farther trees will be more apparent
 
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