Canon 50mm DOF

antonroland

antonroland

Inspector Gadget
Suspended / Banned
Messages
4,210
Name
Anton
Edit My Images
Yes
So I played around a bit recently and was rather disappointed to see that my EF 50mm/1.4 only goes down to f/22.

What to do if I wanted f/3x or f/4x?
 
Why would you want to? Diffraction would make your images very soft at those sorts of apertures.
 
StewartR said:
Why would you want to? Diffraction would make your images very soft at those sorts of apertures.
Click to expand...

I suppose there would not be a noticable improvement in DOF but for the sake of longer exposures it would have been nice.

Why would that make the image soft though? I thought it would have the opposite effect?
 
you need ND filters or lower the ISO if all you want to do is increase exposure time

at very small apertures, especially on wider lenses, the size of the actual hole comes into play

50mm f/20 (I made it up to keep the numbers simple) the aperture is only 2.5mm across
whereas a 500mm at f/20 the hole size is 25mm (1" in old money)

as the hole gets smaller, light gets bent around the edges (diffraction)
it happens at larger diameters but outside the sensor area

I guess the lens makers work out where the diffraction becomes unacceptable and limit the aperture there
 
mmcp42 said:
you need ND filters or lower the ISO if all you want to do is increase exposure time

at very small apertures, especially on wider lenses, the size of the actual hole comes into play

50mm f/20 (I made it up to keep the numbers simple) the aperture is only 2.5mm across
whereas a 500mm at f/20 the hole size is 25mm (1" in old money)

as the hole gets smaller, light gets bent around the edges (diffraction)
it happens at larger diameters but outside the sensor area

I guess the lens makers work out where the diffraction becomes unacceptable and limit the aperture there
Click to expand...

Makes sense, thanks

What is interesting to me is that the f/1.2 L only stops down to 16...:thinking:

One would expect the better (?) lens to be able to stop down further than the prosumer f/1.4 which stops down to 22...:shrug:
 
i would never shoot above f/16 normally - as said i rather use a filter to get the desired effect.
 
antonroland said:
Makes sense, thanks

What is interesting to me is that the f/1.2 L only stops down to 16...:thinking:

One would expect the better (?) lens to be able to stop down further than the prosumer f/1.4 which stops down to 22...:shrug:
Click to expand...

nope
t'other way round
the better lens has higher criteria for quality
so diffraction is less acceptable!
 
Makes sense once again if you think about it that way.

I wonder how many folks on here have the 1.2? And are they really happy with it?

With all the names it is being called, shifty fifty and according to photozone it has rather bad CA in high contrast areas when wide open.

To get back to my original question anyway, the idea of very high f/numbers is settled as a bad idea then...

Cheers all:thumbs:
 
My Dad has a Sigma 50mm Macro that can go down to f45 if that is something you are interested in it might be worth checking that out...
 
antonroland said:
Makes sense once again if you think about it that way.

I wonder how many folks on here have the 1.2? And are they really happy with it?

With all the names it is being called, shifty fifty and according to photozone it has rather bad CA in high contrast areas when wide open.

To get back to my original question anyway, the idea of very high f/numbers is settled as a bad idea then...

Cheers all:thumbs:
Click to expand...

I rented the 1.2 for my trip to Oz
absolutely stunning bit of kit
performed flawlessly in really low light conditions
I'm saving to buy one now (Dear Santa...)
 
You must log in or register to reply here.
Back
Top