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TopBanana

TopBanana

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Tim
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:help:
One of my main reasons for starting in SLR photography is the lack of control of depth of field on a compact, so I'm trying to work out the effects on DOF of changing aperture. My problem is that I'm really just guessing aperture settings in an attempt to get a nice DOF then having to wait until the film is finished and developed before finding out if I'm right.

So my question is does anybody have a camera with a 'DOF preview' button, and if so do you use this feature? [my camera doesn't have this feature and I'm wondering if it's worth upgrading to one that does]
Or did you find that you learnt what each setting did quickly enough to not need to whine :LOL:

Any tips on choosing the right DOF without having to shoot rolls and rolls of film whilst carefully writing down the settings for each shot would be greatly appreciated!
 
Your lens will have a dof scale on the focus ring... but to answer your question pretty much every older film camera will have the dof preview button - the buttons began to disappear as electronics took over and the mechanics of having something moving around inside independently of the shutter/mirror became too expensive and heavy to maintain. Many older lenses will have a manual/auto selector as well to allow the lens to stop down as you turn the aperture ring.
 
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DOF preview is a nice touch but pretty ineffective as a way of ascertaining sharp focus. At smaller F settings the viewfinder is so dark as to be meaningless. Better to use the scale on the lens.

If DOF is crucial as in landscape work, carry a tripod and use F16 or F22. Bear in mind very small aperture settings are for increased depth of field of focus, not absolute resolution. As high F numbers use a tiny piece of glass to focus through (which may have its own abberations) highest resolution is usually in the F8/F11 region for 35mm lenses.
 
The best way to see the effect of DOF changes at the time, is to start wide open and stop down while continuing to look through the viewfinder.

Also, if you are using a prime instead of a zoom you may benefit from using hyperfocal distance to obtain the greatest depth of field for the aperture you are using.
 
... with an eos500n?
 
Thanks for the replies.
I have an EOS 500N which doesn't have the DOF preview or anyway of stopping fown the lens whilst viewing, I don't even think that my lens (the kit lens) has a DOF scale on it! So i'm totally in the dark until I get the prints back.

I've seen a couple of websites that give formulae for calculating DOF, so maybe I should make myself a small crib sheet for different apertures at different focal lengths.

Colpepper I get your point about the viewfinder becoming too dark, but it's more the other end of the scale that I'm interested in, small f-numbers and shallow DOF, so that shouldn't be too much of an issue. I'm still not sure if it's worth changing cameras for though.
 
TBH, I find it's difficult to make an accurate judgement of the depth of field even wide open on 35mm. The viewfinder tends to flatten the differences between things in focus and those not in focus - which is why a split prism and/or fresnel is so useful to get the focus right in the first place.

From what I recall, there's some kind of inverse relationship between the brightness of the viewfinder and accuracy of the representation of focus, depending on the coarseness of the ground glass surface.

I'm frequently surprised at the results on my 5D where I can make an instantaneous comparison, which is 35mm full frame (and has DoF preview). Things turn out much more pronouncedly out of focus than they appeared in the viewfinder, even on the LCD display on the back of the camera, let alone on a computer screen.

On medium format, DoF preview is of more use IME.
 
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I've found DoF preview to be priceless for macro work but near useless for anything else. For things requiring a lot of DoF I use hyperfocal distance focusing and prayers.
 
Mr_T said:
For things requiring a lot of DoF I use hyperfocal distance focusing and prayers.
Click to expand...

Ditto. Truth is objects aren't in focus or out, it's a sliding scale of acceptability that depends on the viewer and how big the image is projected. DOF previews will only give an idea of what's in range, not an absolute guarantee of teeny circles of confusion.
 
Gremlin said:
Don't know if this might help you

http://dryreading.com/camera/index.html
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Thanks for the link, that's website's great fun to play with. I understand the principles of exposure but I'm not totally sure of the depth of field that I'll get in each specific situation.


This morning I was reading 'Understanding Exposure' by Bryan Peterson (which gets a big (y) from me) and he describes the 'poor man's DOF preview' where he said you unscrew your lens by 1/4 turn and this has the same effect as the DOF preview. I haven't had a chance to check this on my camera yet - has anybody else heard of or tried this. Not sure I see why it would work :thinking:
 
So long as you remove the lens from the stop down lever, most lenses will default to the F-stop set. Be careful you don't drop it!
Not sure about Canon, they seem default open.
 
TopBanana said:
This morning I was reading 'Understanding Exposure' by Bryan Peterson (which gets a big (y) from me) and he describes the 'poor man's DOF preview' where he said you unscrew your lens by 1/4 turn and this has the same effect as the DOF preview. I haven't had a chance to check this on my camera yet - has anybody else heard of or tried this. Not sure I see why it would work :thinking:
Click to expand...

From what I remember of old M42 cameras/lenses unscrewing the lens would release the auto-aperture pin, allowing the lens "iris" to close up to the setting on the aperture scale and having the same effect as a DOF button.

Edit: just tried it on the EOS-3 and it doesn't do jack!
 
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TopBanana said:
he describes the 'poor man's DOF preview' where he said you unscrew your lens by 1/4 turn and this has the same effect as the DOF preview. I haven't had a chance to check this on my camera yet - has anybody else heard of or tried this. Not sure I see why it would work :thinking:
Click to expand...

:thinking:

Not sure how I would do that with a Canon EF or FD bayonet mount :)
 
TheBigYin said:
From what I remember of old M42 cameras/lenses unscrewing the lens would release the auto-aperture pin, allowing the lens "iris" to close up to the setting on the aperture scale and having the same effect as a DOF button.

Edit: just tried it on the EOS-3 and it doesn't do jack!
Click to expand...

M42 lenses do it the opposite way around to every other mount (that I know of), the iris only stops down when the pin is pushed in or the iris is set to manual so that when the shutter is pressed a little 'kicker' pushes the pin in and stops it down.
Your thinking of the original mechanical Pentax K-mount, that works like you describe as they have a little spring loaded lug that is tensioned to open the iris fully when mounted on the camera and then released to stop the iris down when the shutter is pressed.
 
s162216 said:
M42 lenses do it the opposite way around to every other mount (that I know of), the iris only stops down when the pin is pushed in or the iris is set to manual so that when the shutter is pressed a little 'kicker' pushes the pin in and stops it down.
Your thinking of the original mechanical Pentax K-mount, that works like you describe as they have a little spring loaded lug that is tensioned to open the iris fully when mounted on the camera and then released to stop the iris down when the shutter is pressed.
Click to expand...
I knew there was one mount that worked that way - to be honest, it's been 25+ years since i've had to mess around with anything like that and at my age, the memory's on it's way out! :shrug:
 
Why don't you just take a photograph at different apertures and review them on screen?
 
aberal said:
Why don't you just take a photograph at different apertures and review them on screen?
Click to expand...

By the time the FILM is developed and scanned, and the images are on screen, the decisive moment for the picture has probably passed!
 
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