Storytelling Apertures and focus

[parkmoy]

Been re-reading 'Understanding Exposure' and found something a bit confusing (to me, anyway!). Peterson talks about setting an aperture of f/22 for maximum depth of field and then using the distance scale on the lens to set the focus. He gives an example of a 20-35mm zoom set at 20mm and he sets the focus at 2 feet.

OK, I understand that, but then he goes on to say 'Your focal length will determine which distance you choose' Again I understand that, but what he doesn't say is how to work out which distance you choose for which focal length.

Am I missing something simple?

 

[mrtoad]

at f22 with a 20mm the dof is fantastic...really a w/a hardly needs to be focussed!!

what he means is if you set your furthest (not always infinity- thats a cop out) and nearest focussing points against the aperture indexes on the lens aperture ring at the aperture you are going to use
then the focus you are using is the one on the middle notch of the ring
....it is bloody confusing to try to tell

will look for a pic

some shots of lens settings
try this for some idea...on nikons they put a colour code so that at f16 you align with the f16 colour...etc

i dont have a dslr so i cant show what it looks like, and i have sold all my 35mm kit

 

[jerry12953]

Unfortunately most lenses these days don't have depth of field scales - especially zooms.

Search on here for "hyperfocal distance" and see what you can find....

 

[mrtoad]

Unfortunately most lenses these days don't have depth of field scales - especially zooms.
Search on here for "hyperfocal distance" and see what you can find....

what a shame

i think some rule of thumb ideas may be needed or a table of dof/focal length/aperture variants

this may do the trick

stop down methods are another way but i suppose modern dslr dont have stop down or mirror lift on the bodies :thumbsdown:..i assume they have mirrors still

 

[parkmoy]

Thanks for the info folks. Much more complicated than I thought. Are there any rules of thumb?

 

[mrtoad]

Thanks for the info folks. Much more complicated than I thought. Are there any rules of thumb?

if you are using autofocus you can spot focus on an item around 30m away and shoot your landscape
then do the same thing for something around 5m away and shoot
unless you want really close things in focus...in which case use aperture priority and focus around 1m behind the closest item at your smallest aperture
and compare again
if your review window has an enlarging facility you can blow up the parts you want sharp and then by comparison choose the one you want ..delete the others

easier is wait till you get home and then review on the pc or laptop

depth of field is only covers acceptable focus which is nearly as sharp as the focal point and not detectably out of focus
outside of this is still acceptable but not by so much and for far objects not even worth bothering about..unless you are shooting the top of a mountain in snow or trees and want sharpness there



see circles of confusion...my middle name..

circles of confusion

 

[parkmoy]

So, you are saying that unless you specifically want the extreme distance in sharp focus, concentrate more on the fore and middle ground?

Great pic by the way

 

[HoppyUK]

The sometimes confusing Mr Peterson is talking about hyperfocal distance.

It's not complicated or difficult, just a way of setting the focusing distance for maximum depth of field from infinity to close distance. It is affected by a few things, but mainly f/number and focal length.

Have a look at this on line calculator and input different lenses and f/numbers to see how hyperfocal distance changes, and how much depth of field you get with different combinations: http://www.dofmaster.com/dofjs.html

 

[parkmoy]

Thanks Hoppy, a very useful calculator to play with and see how the DoF alters.
Just to clarify then, is Peterson recommending setting the camera focus on the distance scale at the hyperfocal distance?

 

[simonkit]

It's a great book & well worth a read, it's more about photography with film though so some of the "technicalities" need a slight tweak for digital..

F22 gives great DOF but unfortunately on crop sensor digital cameras it also creates diffraction problems, resulting in less sharp details.

Using Hyperfocal Distance is also now difficult as DOF scales are rare on new lenses, the principal is well worth knowing though

Simon

 

[HoppyUK]

Thanks Hoppy, a very useful calculator to play with and see how the DoF alters.
Just to clarify then, is Peterson recommending setting the camera focus on the distance scale at the hyperfocal distance?

You're welcome That DoF Master site is excellent for all sorts of depth of field questions and I think a lot of people refer to it.

Yes, it's the hyperfocal distance for maximum depth of field - at any given f/number and focal length. Set that, and everything will be within the zone of acceptable sharp focus, from far distance (infinity) to close up. But the hyperfocal distance moves and the DoF changes with focal length and f/number.

Another handy feature on that site is a PDF rotary DoF calculator you can customise to your specific lenses and print out. Sticking it to your lens caps is a nifty idea When you've done that, you will have a very comprehensive depth of field scale similar to the one printed on some prime lenses (you don't get them on zooms because they would be far too complicated). The calculator is also a very good way of understanding how depth of field works and when it's presented on an analogue scale in that way it's easy to see the factors affecting it and how they relate. You don't even have to print it out for a bit of learning - just rotate the scales on screen to see what's going on. It's here http://www.dofmaster.com/custom.html

Edit: see post #13 below re diffraction

 

[parkmoy]

F22 gives great DOF but unfortunately on crop sensor digital cameras it also creates diffraction problems, resulting in less sharp details.

I vaguely remember seeing a reference to this somewhere in a magazine but I would welcome more detail.

So how do you choose an aperture for landscapes which will give you maximum DoF without diffraction problems? And what exactly are diffraction problems and how do they manifest themselves? Do they vary from lens to lens? Why are they peculiar to crop sensor digital?

 

[HoppyUK]

I vaguely remember seeing a reference to this somewhere in a magazine but I would welcome more detail.

So how do you choose an aperture for landscapes which will give you maximum DoF without diffraction problems? And what exactly are diffraction problems and how do they manifest themselves? Do they vary from lens to lens? Why are they peculiar to crop sensor digital?

It's a good point raised by Simon about diffraction.

It's an aberration that is happening all the time, but only becomes apparent at small f/numbers when the circumference of the aperture relative to its area, becomes significant. Basically, it kills critical sharpness and contrast over the whole picture.

It's an optical effect unrelated to lens design or brand or quality, although it is reduced by the thickness of the aperture blades and the thinner the better, but most lenses are similar in this respect.

It is also subject to format and compacts suffer quite badly, which is why most of them don't go higher than f/8. On crop cameras, if absolute sharpness is a priority over depth of field I think about diffraction at f/11, and think twice at f/16. I don't use f/22 as after doing some tests prompted by a thread on here, it's really rubbish but TBH I can't remember when I ever wanted to use f/22 anyway.

 

[parkmoy]

I've found a site which has mostly clarified diffraction for me and may help others :
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

I'm still wondering what the best aperture for landscapes is on my camera is though. If I've understood it right it would appear to be f/8 - f/11 which seems a very low number.

The more I learn about this game, the more I think that ignorance is bliss and a P&S:bonk:

 

[mrtoad]

So, you are saying that unless you specifically want the extreme distance in sharp focus, concentrate more on the fore and middle ground?
Great pic by the way

hi again
what i have learned and perhaps read is that there is a point at which your lens will resolve far detail satisfactorily enough for general viewing comparable with the properties of the human eye...eagles have better vision of long distances..
so focussing on infinity at one end of your dof for your lens and aperture is a waste of good fore to middle ground capture sharpness
my personal focussing point will vary but i wouldnt put it beyond 50-80 metres
so i can concentrate on the nearer elements in view as more profitable to be in sharp focus and so make the further appear further away by association and relative sharpness perspective...sort of a tunnel of sharp to 'unsharp' if there is such a thing
for landscapes i search out the foreground and middle ground elements which can leap out at the viewer if sharp enough
the closer ones determine my nearest focussing point and 50-80 my furthest

its all a bit theoretical because now i dont have lenses with markings and merely choose an item an focus on that using the aperture priority function and set that at a guess for my 38mm (35mm equivalent) lens setting for what i consider would be the dof for that aperture
my camera only does up to f8 and i consider f5.6 being ok for 5-80 metres general shooting
if i want to do some wowowowo shots of little flowers against mountain peaks i set the thing at f8 and then focus around 0.5m beyond the bonny wee plant...
i am sorry i cant really be more exact but once you get to know your camera from many results you get to just 'feel' what is right...and remember you can take a couple or two at varying settings and edit out there and then
that mountain shot was focussed on the tree line and the lower slopes of the mountain
with autofocus it has to have something to differentiate in contrast to focus so infinity is out!!
hope that helps...what a lot of guff eh?

just focussed on the closer rocks 1/200 f8

 

[parkmoy]

what a lot of guff eh?

But very helpful 'guff '

 

[HoppyUK]

hi again
what i have learned and perhaps read is that there is a point at which your lens will resolve far detail satisfactorily enough for general viewing comparable with the properties of the human eye...eagles have better vision of long distances..
so focussing on infinity at one end of your dof for your lens and aperture is a waste of good fore to middle ground capture sharpness
my personal focussing point will vary but i wouldnt put it beyond 50-80 metres
so i can concentrate on the nearer elements in view as more profitable to be in sharp focus and so make the further appear further away by association and relative sharpness perspective...sort of a tunnel of sharp to 'unsharp' if there is such a thing
for landscapes i search out the foreground and middle ground elements which can leap out at the viewer if sharp enough
the closer ones determine my nearest focussing point and 50-80 my furthest

its all a bit theoretical because now i dont have lenses with markings and merely choose an item an focus on that using the aperture priority function and set that at a guess for my 38mm (35mm equivalent) lens setting for what i consider would be the dof for that aperture
my camera only does up to f8 and i consider f5.6 being ok for 5-80 metres general shooting
if i want to do some wowowowo shots of little flowers against mountain peaks i set the thing at f8 and then focus around 0.5m beyond the bonny wee plant...
i am sorry i cant really be more exact but once you get to know your camera from many results you get to just 'feel' what is right...and remember you can take a couple or two at varying settings and edit out there and then
that mountain shot was focussed on the tree line and the lower slopes of the mountain
with autofocus it has to have something to differentiate in contrast to focus so infinity is out!!
hope that helps...what a lot of guff eh?

just focussed on the closer rocks 1/200 f8

What camera is it you are using that only goes to f/8? It sounds like a compact, and they naturally have massive depth of field as a function of their tiny format sensors.

If this is the case, with a 38mm equivalent focal length lens on an average compact, set at f/5.6, you have depth of field available from under 1m to infinity. It is very hard to not get everything in focus with a compact

Edit: pic isn't showing for me?