Narrow Apertures..

As im climbing the learning curve of DSLR Phoography with my SLR, I havn't as yet needed to go to really 'narrow' apertures ( ie. beyond f11)...I have used f11 mostly for landscapes to get sharp focus front and back, but curious as to what photographic conditions would you use really narrow apertures, such as f16 and beyond?

Would it be purley for long exposures with slow shutter speeds ( ie. night time city shots etc) or are there more creative uses for such narrow apertures?

also, would using an aperture that narrow result in image degredation?

( I already have & read the book ' understanding exposure')

Hey,

If you've already read the book Understanding Exposure - perhaps you haven't understood it all very well?

Because from reading your OP it sounds like you think as you stop a lens down (i.e: go FROM f/5.6 to f/9) the DOF gets NARROWER? This isn't the case. As you stop a lens down you get MORE DOF, not a narrower DOF..

So you'd use something like f/8, f/9, f/10 for landscapes, to get more DOF, and therefore to have more IN focus.

You'd use a narrow depth of field (by using a LARGE aperture [but remember, LARGE aperture, means LOW aperture VALUE - f/11 is small, f/2.8 is large - f/2.8 results in shallower, or narrower depth of field.]).. anyway, you'd use a shallow depth of field for various things. Portraits, where you want the background smoothly blurred, or in lots of sports photography - eg: football when you only want your player in focus, and the background, AND land IN FRONT OF the player out of focus.

And you asked, does narrower DOF results in degraded image quaity? It depends.

When using your kit lens, YES - at f/8 it'll be nice and sharp, but wide open at f/3.5, it'll be sharp enough - but not half as sharp as when stopped down to f/8. With more expensive lenses, I'm guessing all the L family, IQ SHOULD be the same throughout the aperture range...

Hopefully this has helped your understanding of the relationship between DOF and Aperture a bit more.....

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I presume you know the DOF calculations (see http://www.dofmaster.co.uk ).

Smaller appertures will allow a closer Hyperfocal distance with a distant focus subject.

As for distortion, you dont mention which camera you have. (I have a 350D).

On the 350D, f/16 is the smallest you should go before distortion. The 400D has smaller cells (same APS-C sensor but more elements) so I presume f/11 or f/13 is the limit.

I have seen some extreme calculations, based on 6.2micron sensor cells of the 350D, and the wavelengths of red, green and blue light, that suggest a theoretical min apperture of f/7.4 before distorion occurs. I dont agree with the theory behind these particular calcs.

In my experience, f/13 is the sharpest I can get, if I go to f/16 or beyond, I can just start to see pixel distortion

Olie,

You might reread the OP's post.... He understands perfectly.

That's why he said Narrow aperture not narrow DOF

And he appropriately used f11 to get sharp pictures in a landscape.

He was just asking why he should go narrower. The answer is: to get even wider DOF.... such as a landscape background in focus with an extremely close subject.

Or, to get a longer exposure of a bright scene. (waterfalls in motion, etc)

Ryan

GreenPig said:

I presume you know the DOF calculations (see http://www.dofmaster.co.uk ).

Click to expand...

This link doesn't work, by the way.

And by narrow, I believe he meant narrow (small opening with a higher aperture number).
--
http://www.pbase.com/a37licia

Canon 350D
kit lens
SIGMA 70-300mm DG
Canon 50mm f1.8 II
Speedlight 430ex

bluefox9er said:

night time city shots etc) or are there more creative uses for such
narrow apertures?

Click to expand...

As you go narrow, bright lights bleed out as stars. Who thinks diffraction at that point
Examples below

F/16



F/22



--
PicPocket
http://pictures.ashish-pragya.com/GalleryIndex.html

nice tip! thanks!

tend not to go beyond f11 for landscape shooting nowadays, mainly for fear of diffraction issues (making the image less sharp).

if you want blurring of waterfall (etc)....again it is probably advisable to use a nd filter and shoot them on particular days when it is not too bright to get the desired effect and avoid diffraction as mentioned above.

but the above also depends what sort of lenses you use (imo).

the only time i tend to shoot beyond f11 nowadays is when i am shooting macros of insects. i generally tend not to go beyond f16 (occasionally f18). i haven't mastered the ability to shoot tiny insects at multiple frames/layers and composing them together to get an increase in dof effect. so this is my lazy way of correcting that problem to some effect.

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http://www.pbase.com/antidote3

Because of the very narrow DOF at higher magnifications most macro work with DSLRs uses apertures between f11 and f22.

The problem with very small apertures (f16 and above) is diffraction which tends to blur the image (note: diffraction effects start at wider apertures than f16, but I've not noticed image degradation in my macro photographs with a 300D until f16 is reached).

--
You want macros? We got 'em! Check out:
http://www.pbase.com/cjed

correct link - http://www.dofmaster.com

I've just re-read the OP - You're totally right... Must have read it too quick and presumed 'narrof DOF'.. sorry about that! (Oh well hopefully my basic lecture on something the OP didn't even ask for, will benefit someone else some time! lol)

moondawg14 said:

Olie,

You might reread the OP's post.... He understands perfectly.

That's why he said Narrow aperture not narrow DOF

And he appropriately used f11 to get sharp pictures in a landscape.

He was just asking why he should go narrower. The answer is: to get
even wider DOF.... such as a landscape background in focus with an
extremely close subject.

Or, to get a longer exposure of a bright scene. (waterfalls in
motion, etc)

Ryan

Click to expand...

--

Olie Dellar said:

I've just re-read the OP - You're totally right... Must have read it
too quick and presumed 'narrof DOF'.. sorry about that! (Oh well
hopefully my basic lecture on something the OP didn't even ask for,
will benefit someone else some time! lol)

Click to expand...

Lol..that's ok..I have been using very wide apertures to create the blurry background effect with shallow DOF, and using a wider DOF to get crispish landscape shots ( with the limitations of the kit lens, ive been very naughty with buying too much gear, so no WA lens until next year!).

I was just curious what practicle uses or scneraios there would call for going beyond f11,f16 etc.

bluefox9er said:

As im climbing the learning curve of DSLR Phoography with my SLR, I
havn't as yet needed to go to really 'narrow' apertures ( ie. beyond
f11)...I have used f11 mostly for landscapes to get sharp focus front
and back, but curious as to what photographic conditions would you
use really narrow apertures, such as f16 and beyond?

Click to expand...

Depending on the DSLR that you have, you will most likely notices softness due to diffraction at around f11 to f13.

See link for more information on diffraction.
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

It has a diffraction calculator and graphic representations of the airy disks superimposed on a pixel grid to show diffraction.

bluefox9er said:

What photographic conditions would you
use really narrow apertures, such as f16 and beyond?

Click to expand...

Macro photography is just one example.

In my experience, going smaller than f16 on the XTI hurts the sharpness of the image too much to be useful. I recently did a flower macro with the kit lens and 12mm extension tube. I was using A-DEP mode to try to get all the parts of the flower in focus and the camera came up with f29. I actually found the result to be not all that bad (yes it was soft, but it was soft all over and everything looked equally in focus) except for the fact that it revealed a lot of sensor dust, which I didn't know that I had on my XTI.