Stop down metering - OVF and EVF

[goinggreynow]

Hopefully there are some fellow members who can put me straight here. I've read numerous articels, but am still confused!
I am trying to help someone (not a member of TP) using legacy glass on a Canon EOS body. Although I am also a Canon shooter, my use of old legacy glass is currently on my Panasonic G80. So i have some experience of using adapted lenses through an EVF ,but zero when it comes to an OVF.
I apologise for what will be some very basic questions here.
a) Am I correct in assuming that there is little (no) reason to consider stop down metering when using a (modern) EVF? I have been happily using my Zuiko and Minolta lenses on my G80 in full manual mode by setting the required aperture on the lens, dialling in the shutter speed and then balancing things out with auto ISO. A quick look at the meter tells me if I am under or over exposed.
b) Presumably the main issue with an OVF is that if you meter at anything other than the widest aperture then the view through the OVF becomes progressively darker to the point that you cannot reliably focus manually? Is this the only reason for stopping down or am I completely missing the point?
c) If you have an OM-EOS lens adapter with a focus confirmation chip, does this lessen/negate the neeed to stop down meter or is it simply not relevant?
d) Do some adapters "play" nicer with Canon bodies than others?
I suspect I may have to purchase my own adapter for my Canon body and give things a go myself, but I thought it wise to ask for any pointers here first.
many thanks

 

[sk66]

I can only speak to the first two questions... Yes and Yes.

 

[stevelmx5]

a) An adaptor to mount the lens to the body will generally have a part built in to press a small pin on a lens (such as OM Zuiko) which stops the aperture down permanently. Therefore, when you set the aperture on the lens, the actual aperture blades stop down to that aperture immediately. In a sense, you are always using stop-down metering as otherwise the camera's light meter can't determine the correct shutter speed/ISO for the aperture as the lens would always be wide open. Film SLR's used to only press that pin at the time of exposure so the aperture 'stops down' to the metered setting but you can always focus with the aperture wide open to keep the OVF bright.

b) Yes - When you stop down the aperture on the lens, less light gets through to the OVF so it get's darker. An EVF gives you the option to 'gain up' the view so even though the aperture is narrower, the brightness of the EVF doesn't change (like bumping up the ISO for your exposure, but within the EVF)

c) Focus confirmation has nothing to do with metering. The chip just gives a visible/audible response when a set focus point is judged as being sharp.

d) Some adaptors will be made with tighter tolerances than others so you don't get any play on the lens/body. Realistically, the adaptors are generally just a tube with a male EF mount at one end and a female OM mount (for example) on the other with the right length to account for the difference in flange depth between Canon/Olympus.

 

[Mr Perceptive]

The first thing to consider is the fact that any adapter added to a Canon DSLR will very likely act as an extension tube and you will not obtain infinity focus, on the Panasonic the adapter placed the lens at the correct point as if it was on an SLR.

This may be a show stopper and mean that the project doesn't move forward at all!!!!

 

[woof woof]

The first thing to consider is the fact that any adapter added to a Canon DSLR will very likely act as an extension tube and you will not obtain infinity focus, on the Panasonic the adapter placed the lens at the correct point as if it was on an SLR.

This may be a show stopper and mean that the project doesn't move forward at all!!!!

That's not quite right as it's no different to using mirrorless in that the adapter acts as a mount adapter and a spacer to set the correct registration distance. Manual film era Oly om lenses and others will work fine on a Canon dslr and you'll get infinity focus. The only time there's a problem is if the registration distance can't be achieved by the adapter such as with Canon FD or Minolta SA and in cases like these you do lose infinity unless there's a corrective lens in the adapter.

 

[Mr Perceptive]

That's not quite right as it's no different to using mirrorless in that the adapter acts as a mount adapter and a spacer to set the correct registration distance. Manual film era Oly om lenses and others will work fine on a Canon dslr and you'll get infinity focus. The only time there's a problem is if the registration distance can't be achieved by the adapter such as with Canon FD or Minolta SA and in cases like these you do lose infinity unless there's a corrective lens in the adapter.

Ok I hadn't clocked that the Canon EOS focal plane distance is shorter than most of older film based DSLRs, though obviously you would have to check that any purchased adapter is no too 'thick' so as to act as an extension tube

 

[stevelmx5]

Ok I hadn't clocked that the Canon EOS focal plane distance is shorter than most of older film based DSLRs, though obviously you would have to check that any purchased adapter is no too 'thick' so as to act as an extension tube

The adaptors are machined specifically for each mount so if you buy an OM-EF mount (for example), it will be the correct flange depth.

 

[john.margetts]

The first thing to consider is the fact that any adapter added to a Canon DSLR will very likely act as an extension tube and you will not obtain infinity focus, on the Panasonic the adapter placed the lens at the correct point as if it was on an SLR.

This may be a show stopper and mean that the project doesn't move forward at all!!!!

I successfully use both M42 screw mount and Olympus OM bayonet mount lenses on my Canon EOS cameras. Focusing is easy before setting the aperture (ie, set the lens aperture to its widest to focus) and then close the aperture to the required value to let the camera meter. Old lenses always have to be used Av or Manual.[/I]

 

[goinggreynow]

many thanks for all the replies. Most helpful.

a) An adaptor to mount the lens to the body will generally have a part built in to press a small pin on a lens (such as OM Zuiko) which stops the aperture down permanently. Therefore, when you set the aperture on the lens, the actual aperture blades stop down to that aperture immediately. In a sense, you are always using stop-down metering as otherwise the camera's light meter can't determine the correct shutter speed/ISO for the aperture as the lens would always be wide open. Film SLR's used to only press that pin at the time of exposure so the aperture 'stops down' to the metered setting but you can always focus with the aperture wide open to keep the OVF bright.

b) Yes - When you stop down the aperture on the lens, less light gets through to the OVF so it get's darker. An EVF gives you the option to 'gain up' the view so even though the aperture is narrower, the brightness of the EVF doesn't change (like bumping up the ISO for your exposure, but within the EVF)

c) Focus confirmation has nothing to do with metering. The chip just gives a visible/audible response when a set focus point is judged as being sharp.

d) Some adaptors will be made with tighter tolerances than others so you don't get any play on the lens/body. Realistically, the adaptors are generally just a tube with a male EF mount at one end and a female OM mount (for example) on the other with the right length to account for the difference in flange depth between Canon/Olympus.

re point A/B above, so the only way to get round the "dimmer" OVF - if needed - would be to focus using say F2.8 and then manually stop down to say F11 and then take the photo - very much a 2 part process?
re C. Thanks, i appreciate that focus confirmation has nothing to do with metering - I was just wondering if the focus confirmation assist would mean that there was less of a need to open up the aperture to Say F2.8, to focus before stopping down again. I'm not too sure how the focus confirmation chips work on these adapters.
Thanks again.

 

[stevelmx5]

many thanks for all the replies. Most helpful.



re point A/B above, so the only way to get round the "dimmer" OVF - if needed - would be to focus using say F2.8 and then manually stop down to say F11 and then take the photo - very much a 2 part process?
re C. Thanks, i appreciate that focus confirmation has nothing to do with metering - I was just wondering if the focus confirmation assist would mean that there was less of a need to open up the aperture to Say F2.8, to focus before stopping down again. I'm not too sure how the focus confirmation chips work on these adapters.
Thanks again.

With regards to OVF brightness, yes the only way to get around it is to focus at 2.8 then stop down the lens to the aperture you want to shoot at.

Sorry, didn't mean to teach you to suck eggs with the focus confirm. You could rely on the AF confirm chip but it's probably easier to just focus at 2.8 and stop down afterwards if the OVF is too dark.

 

[goinggreynow]

With regards to OVF brightness, yes the only way to get around it is to focus at 2.8 then stop down the lens to the aperture you want to shoot at.

Sorry, didn't mean to teach you to suck eggs with the focus confirm. You could rely on the AF confirm chip but it's probably easier to just focus at 2.8 and stop down afterwards if the OVF is too dark.

Hi Steve,
Many thanks. Much appreciated. Probably the best thing for me to do here is to get hold of an adapter myself so that I can use my Zuikos, Helios and Pentacons on my Canon (I'm starting to build up quite a little collectiona and it needs to stop!).. At the moment, I'm using the lenses only on my Panasonic with its EVF. Quite apart from trying to help a fellow user, it would be a good learning experience for me too.
Regards
Stuart