Largobob

Thanks BebuLamar. Makes perfect sense. Now you have peaked my curiosity....to look more closely at the camera body/lens interface.

amfoto1 Loc: San Jose, Calif. USA

I just checked the manual for Canon M5 and it states that the aperture is maintained fully open until the moment of exposure. (Same as SLRs & DSLRs have done for the last 30 or 40 years... FWIW, when this feature was first introduced in the mid-1960s, parallel with the earliest versions of Through The Lens metering, it was often referred to as "auto aperture". But just to be clear, it was not "auto exposure". Older cameras controlled the aperture mechanically, via a lever or pin. In the late 1980s manufacturers started converting to electronic aperture control... which made sense since they were already having to implement electronic communication between camera and lens to accommodate then-new autofocus).

Presumably, the same is true of all the Canon mirrorless models.

And, of course, it would be limited to native lenses designed to work with the camera. Adapted vintage lenses with a fully manual/mechanically controlled aperture would need to actually stop down.

With other brands of mirrorless, simply look to see if the camera has a "depth of field preview" feature. If it does, then it must maintain it's native lenses wide open until the instant of exposure. If it doesn't have a DoF preview feature, it might allow the lenses to stop down (and the electronic viewfinder compensates for the reduction in light). But I still doubt it....

As a previous response points out, reducing the light by allowing the aperture to actually stop down would also seriously effect autofocus performance. At some point, probably around f/8, AF would be slow and struggle a lot even in "good light"... in poor light or at even smaller apertures it would fail completely. For this reason, I suspect most (all?) mirrorless maintain a fully open aperture until the instant of exposure... to provide as much light as possible for the camera to be able to autofocus in as wide a range of ambient light conditions as possible.

IDguy Loc: Idaho

It seems to me that if the mirrorless is to give you WYSIWUG in the viewfinder it has to stop down the lens...probably when you half press the shutter release to focus.

Nikon is promising an adapter for their new mirrorless to use DSLR lenses. They already have one for their discontinued V1 mirrrorless. It will be interesting to see what the new one does and would be interesting to know what their existing one does.

amfoto1 Loc: San Jose, Calif. USA

Well, it doesn't.

At least I can say for certain that the Canon mirrorless don't. Same as SLRs and DSLRs, what you see in the viewfinder represents the shallowest possible depth of field... unless you use a depth of field preview feature (assuming the camera has one).

And I think it's pretty safe to assume other mirrorless don't stop down until the very instant of exposure, either, because it would cause serious problems with autofocus to do so.

HarryBinNC Loc: Blue Ridge Mtns, No.Carolina, USA

My mirrorless cameras - Fuji & Panasonic - keep the aperture wide open until shutter release just like an SLR - the cameras adjust finder brightness according to aperture and shutter adjustments to make the WYSIWYG work. The Fuji’s also have a depth of field scale across the bottom of the finder image that responds to aperture changes.

f8lee Loc: New Mexico

While my FUji lenses do keep the aperture opened, I also see my non-Fuji manual lenses (like the 7 Artisans 7.5MM f2.8 fisheye) does close down the diaphragm as I turn the aperture ring. But it's no surprise, the EVF can take into account the 8+ stops of ND filter that I use on other lenses; looking through the viewfinder you cannot tell the ND is there at all.

IDguy Loc: Idaho

Interesting. I can see that they could adjust EVF electronically for exposure. Thanks.

User ID

`

You will encounter various protocols for aperture action
on live view cameras and live modes of SLRs. One reply
above says the Canon M5 uses the normal SLR protocol.
However true that may be, never assume it's the model
for all live view cameras. Use of a "smart" adapter can
result in a different protocol than would be used with a
native lens. Worse yet, some live view cameras will use
different protocols with different native lenses.

Example of a really odd protocol with certain Sonys and
particular Sony lenses:

If you set a wide aperture, the lens views at that same
aperture. If you set very small one, it views half open.
Depending upon the available light, AF activation might
open the aperture to improve signal, but it also might
initially AF at mid-aperture and then pop to fully open
for a final check ... and acoarst stop down to working
aperture for exposure.

Given sufficient available light, there is good rationale
behind initiating AF at a mid-aperture: The DoF at such
stops makes the subject detail more evident to the AF
system, thus avoiding AF Hunting. But that same DoF
could mask a minor AF error, so the final check occurs
at fully wide open.

Basically, iris protocols for live view form a "crazy quilt".
Those who try to figger it all out by very knowledgeably
observing their own camera and lens can well be misled
becuz there are so many variables and it's very unlikely
that all variables will be involved in their observation of
the particular gear-at-hand and in the particular context
of their limited observations.

The answer to the OP is that there is no one answer,
even for any one brand of gear.

`

twowindsbear

Why don't you just look into the lens, look at the diaphragm, as you adjust the f-stop and see for yourself - then set the f-stop to f16 and watch the diaphragm as you trip the shutter? Then report back what actually happens and end this endless speculation.

BebuLamar

Good idea but I don’t have one and I don’t think they all work the same way.

camerapapi Loc: Miami, Fl.

"Generally speaking, for almost all modern cameras,the aperture stays open until the moment the picture is taken. Things like auto focus for instance would really struggle to operate with a lens stopped down. Not to mention the operator's struggle to frame the shot."

wmurnahan Loc: Bloomington IN

Sony is at the set aperture so you see the depth of field, the image you view in the view finder is what the picture will look like.

wmurnahan Loc: Bloomington IN

Nope, Sony is always at working aperture. You are viewing the picture you will end up with. Can't speak for the others.

wmurnahan Loc: Bloomington IN

On the Canon FD lenses I use on my Sony, I move the stop down lever to the locked stopped down position, set my Sony to aperture auto or manual and as has been pointed out, I don't see any darkening when I go from 1.8 to 22 because the electronics give me the correct, end product, picture.

Bill_de Loc: US

Now that seems to make sense.

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