Sony lens aperture function

SQLGuy said:

This should be posted as a sticky at the top of the forum.

Default behavior for E-mount is to set the lens to selected aperture immediately in M or A mode, and keep it there. In P or S mode, it will tend to stay open.

When focusing, if previously stopped down, the lens may open back up a bit to acquire focus, then it will stop back down again to meter, and maybe to fine-tune focus.

If Setting Effect is off, the lens will behave the same in A and M modes as it does in P and S modes - that is, it will stay wide open and open stop back down after focus is acquired.

All of the above is for AF-S, and with most E-mount lenses.

In AF-C, the lens will stay stopped down while the shutter button is held or half-pressed... so shot-to-shot focusing in continuous shooting is done stopped down. However, if the shutter button is released, focus acquisition the next time it is pressed is the same as in AF-S.

For a few lenses, like the 24-70GM, the lens stops down immediately even if setting effect is on. Sony has supposedly done this to mitigate focus shift issues seen with these lenses.

And, yes, for the most part, this is something that EVF/mirrorless cameras do differently than OVF cameras... light gain through the EVF makes composition and focusing wide open mostly unneccesary. Metering stopped down is more accurate, and composing stopped down allows continuous display of actual depth of field with no worries about focus shift when you take the shot.

The main complaint about this behavior that I have seen here is from people that shoot at small apertures in the studio, using lenses with the focus shift issues, and have a workflow where they keep the shutter button half-pressed (or BBF button pressed) and use AF-C to follow their subjects. It doesn't take as much light to track as it does to initially acquire focus, but, if your subject is moving around a lot, and the ambient light is low, it can be hard to keep a lot with the lens stopped down.

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SQLGuy said:

If a lens has focus shift, then focusing wide open may be faster, but it won't be more accurate.

The A7 series, at least on most native lenses, as I mentioned, does open the aperture back up for initial focus acquisition anyway. How much it opens back up seems to be ambient lighting dependent.

A big part of why SLTs and SLRs focus faster in low light is because their dedicated PDAF sensels are cross type and are much bigger than the ones embedded in mirrorless sensors.

Metering stopped down is more accurate, regardless.

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Mike Fewster said:

SQLGuy said:

If a lens has focus shift, then focusing wide open may be faster, but it won't be more accurate.

The A7 series, at least on most native lenses, as I mentioned, does open the aperture back up for initial focus acquisition anyway. How much it opens back up seems to be ambient lighting dependent.

A big part of why SLTs and SLRs focus faster in low light is because their dedicated PDAF sensels are cross type and are much bigger than the ones embedded in mirrorless sensors.

Metering stopped down is more accurate, regardless.

Click to expand...

Metering stopped down is theoretically more accurate but not in practice. It is only true if there is enough light to work with and that's the problem. If this wasn't the case, there would be no need for the hybrid sometimes closing down and sometimes not behaviour of the emount lenses that you have already described.

The pdaf system, works better on mirror cameras not because of the size of the sensors but because the mirror can be used to make a wider reflection to the external sensors that measure the differences that are used to calculate focus. Think of it like on a rangefinder camera where the wider apart the two lenses are that are making the readings, the faster and more accurate will be the parallax difference readings that are used to do the focus. On a mirrorless camera, those points are embedded into the sensor and this makes the measurements considerably more difficult. But the on sensor technology is certainly improving.

Click to expand...

SQLGuy said:

Mike Fewster said:

SQLGuy said:

If a lens has focus shift, then focusing wide open may be faster, but it won't be more accurate.

The A7 series, at least on most native lenses, as I mentioned, does open the aperture back up for initial focus acquisition anyway. How much it opens back up seems to be ambient lighting dependent.

A big part of why SLTs and SLRs focus faster in low light is because their dedicated PDAF sensels are cross type and are much bigger than the ones embedded in mirrorless sensors.

Metering stopped down is more accurate, regardless.

Click to expand...

Metering stopped down is theoretically more accurate but not in practice. It is only true if there is enough light to work with and that's the problem. If this wasn't the case, there would be no need for the hybrid sometimes closing down and sometimes not behaviour of the emount lenses that you have already described.

The pdaf system, works better on mirror cameras not because of the size of the sensors but because the mirror can be used to make a wider reflection to the external sensors that measure the differences that are used to calculate focus. Think of it like on a rangefinder camera where the wider apart the two lenses are that are making the readings, the faster and more accurate will be the parallax difference readings that are used to do the focus. On a mirrorless camera, those points are embedded into the sensor and this makes the measurements considerably more difficult. But the on sensor technology is certainly improving.

Click to expand...

Click to expand...

theglassman said:

Interesting to note that adapted lenses on my A7rii ie my canon 85 1.2 on the MC-11 remain wide open stop down on shutter release.

I have noticed that aperture function is not always achieved after the first shot in a continuous sequence as i dont think the aperture function is relayed quick enough to open/close!

Also interesting to note that I've only just realised this after shooting the A7 series since it was released. When shooting Canon glass on the A7rii stopped down I certainly dont look for the actual dof achieved of my selected aperture.

Right now, I'm not sure how i feel about it.

Canon anyone point me to where Setting Effect is on the Menu??

Thanks

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Mike Fewster said:

The pdaf system, works better on mirror cameras not because of the size of the sensors but because the mirror can be used to make a wider reflection to the external sensors that measure the differences that are used to calculate focus.

Click to expand...

Mike Fewster said:

Here's a more technical explanation with diagram.

http://www.mattgrum.com/photo_se/af_diagram.png

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Mike Fewster said:

The size and separation between the pair of AF sensors determines the accuracy of the AF measurement.

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Mike Fewster said:

However there is a trade off - the further apart they are, the wider the aperture must be in order to direct light to reach both sensors.

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SQLGuy said:

Mike Fewster said:

SQLGuy said:

If a lens has focus shift, then focusing wide open may be faster, but it won't be more accurate.

The A7 series, at least on most native lenses, as I mentioned, does open the aperture back up for initial focus acquisition anyway. How much it opens back up seems to be ambient lighting dependent.

A big part of why SLTs and SLRs focus faster in low light is because their dedicated PDAF sensels are cross type and are much bigger than the ones embedded in mirrorless sensors.

Metering stopped down is more accurate, regardless.

Click to expand...

Metering stopped down is theoretically more accurate but not in practice. It is only true if there is enough light to work with and that's the problem. If this wasn't the case, there would be no need for the hybrid sometimes closing down and sometimes not behaviour of the emount lenses that you have already described.

The pdaf system, works better on mirror cameras not because of the size of the sensors but because the mirror can be used to make a wider reflection to the external sensors that measure the differences that are used to calculate focus. Think of it like on a rangefinder camera where the wider apart the two lenses are that are making the readings, the faster and more accurate will be the parallax difference readings that are used to do the focus. On a mirrorless camera, those points are embedded into the sensor and this makes the measurements considerably more difficult. But the on sensor technology is certainly improving.

Click to expand...

Click to expand...