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Official Talk Leica thread
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For clarification I was just trying to point out that it's not all manual lenses that stop down as soon as the aperture ring is adjusted as was implied (or at least how I interpreted it) by one of your posts. Obviously I didn't get my point across very well
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Maybe there is some confusion. All manual lenses for mechanical film cameras (like Olympus OM) rely on a physical linkage to enable the aperture stop down. Adaptors to use these on digital mirrorless bodies then have a matching physical stop built in to them to enable it (all the time, regardless of what the camera body is doing)
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I stand corrected (only slightly I guess
), that OM1 is in essence doing what digital does, via mechanical meansThanks
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It's not :0) An OM1 (and most other mechanical analogue cameras) doesn't stop down the aperture to the figure set on the aperture ring until you fire the shutter. At that point, a mechanical linkage moved the rotating arm on the back of the lens which then stops down the blades to the figure set on the aperture dial. Until this, the lens is wide open so you can manually focus at 1.8/2.8/3.5 etc (depending on the lens' maximum aperture).
When you mount an OM lens to an adaptor for any mirrorless body, the fixed stop pin inside the adaptor turns the rotating arm on the back of the lens and engages the stop down function. As a result, whenever you turn the aperture ring on the lens (whether it's mounted on a body or not), the aperture blades close accordingly.
No mirrorless body has any physical control of legacy lenses like OM Zuikos. The body just reacts to the amount of light reaching the sensor by either increasing the shutter speed or the ISO according to the aperture and mode you're shooting in.
When you mount an OM lens to an adaptor for any mirrorless body, the fixed stop pin inside the adaptor turns the rotating arm on the back of the lens and engages the stop down function. As a result, whenever you turn the aperture ring on the lens (whether it's mounted on a body or not), the aperture blades close accordingly.
No mirrorless body has any physical control of legacy lenses like OM Zuikos. The body just reacts to the amount of light reaching the sensor by either increasing the shutter speed or the ISO according to the aperture and mode you're shooting in.
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Which is how digital cameras with digital lenses work, but if you mount a analogue/"legacy" lens on a digital camera, then the aperture is permanently (sic) set to whatever you select it to be
Over on the Leica SL forum, four pages of dialogue and I actually found a resolution to my issue. The AF works MUCH better with increased exposure levels.
The example at the office party,
For a start the room wasn't that poorly lit - which was one of the catalysts for my frustration. I called it low light, but really it was nothing like end of the night disco lights only, "low light".
The background to the subject was better lit than the subject, metering evaluated the entire scene, therefore the average left the subject underexposed.
So AF on underexposed subjects is seemingly poor.
I just tested this on louise, spot metering with single point AF
-2 EV comp - Did not manage focus
-1 EV comp - 50/50 with hunting
0 EV comp - Good hit rate
The example at the office party,
For a start the room wasn't that poorly lit - which was one of the catalysts for my frustration. I called it low light, but really it was nothing like end of the night disco lights only, "low light".
The background to the subject was better lit than the subject, metering evaluated the entire scene, therefore the average left the subject underexposed.
So AF on underexposed subjects is seemingly poor.
I just tested this on louise, spot metering with single point AF
-2 EV comp - Did not manage focus
-1 EV comp - 50/50 with hunting
0 EV comp - Good hit rate
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Not exactly.
If you have scene wide metering, then you may need to increase compensation so that the subject is brighter, if the subject is made to be underexposed.. that is
IF you have it on spot metering, 0 might be ok
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You said it didn't focus if you increased it
I said the opposite
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You only told us -2 -1 and 0, what about +1 +2 +3? As the Fuji needs to be above to a good one in low light.
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So you're saying the when you spot meter on the subject and then overexpose it, the camera focusses more reliably? Isn't that the same as getting more light onto the subject, just using exposure instead? The only issue is that if you're hitting the wall of the aperture at F4, you need to either bump up the ISO or slow down the shutter speed. Bumping the ISO shouldn't be a major issue unless you're in pith black but slowing the shutter is then going to induce blurring instead.
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That was my point Steve more light should make it easier to focus which is what the over exposing is doing. However we call it over exposing but it might be just right.
Maybe a higher iso would be better.
That's because I was testing it with spot to rule out the background, not evaluative. 100% hit at 0 from a few tests.
If I was doing evaluative then I would have needed +1 or so because I was possibly introducing a bright background into the equation.
No when I spot meter the subject it focussed well at 0 eV comp, I didn't need to over exposure with spot.
But I may need to with evaluative metering of the whole scene.
If the exposure level on the subject is just -1 eV the af fails pretty quickly.
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There's your issue don't simulate then! It's a Leica not a Nikon. It's not made for hard work. It's made to render beautifully.
There's your issue don't simulate then! It's a Leica not a Nikon. It's not made for hard work. It's made to render beautifully.
Erm my test was the simulation.. of the original issue.
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EVF is brighter I assume and therefore can see the image to focus on. It's all electronic so should be easier. Don't shoot me I'm just guessing
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AF speed is reliant on the light entering the camera. Purely changing the exposure does not change the light entering the camera (unless as discussed before you're using legacy lenses with an adapter so the aperture stops down prior to taking the shot). Clearly there's something weird going on as Dan says AF is affected by changing the exposure compensation, but god knows why/how
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by exposing the camera manually altering the exposure compensation as its mirrorless and all electronic the screen is how the camera sees it oppose to a normal camera which doesn't have that luxury.May have something to do with the contrast level detection they use.AF speed is reliant on the light entering the camera. Purely changing the exposure does not change the light entering the camera (unless as discussed before you're using legacy lenses with an adaptor so the aperture stops down prior to taking the shot). Clearly there's something weird going on as Dan says AF is affected by changing the exposure compensation, but god knows why/how
AF speed is reliant on the light entering the camera. Purely changing the exposure does not change the light entering the camera (unless as discussed before you're using legacy lenses with an adapter so the aperture stops down prior to taking the shot). Clearly there's something weird going on as Dan says AF is affected by changing the exposure compensation, but god knows why/how
Tested with Leica Q, it fails at -3 EV in this scenario.
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Again, you're not changing the light entering the camera. All you're doing by changing the exposure is changing the gain on the EVF/LCD, the camera is not magically producing more light from somewhere
Again, you're not changing the light entering the camera. All you're doing by changing the exposure is changing the gain on the EVF/LCD, the camera is not magically producing more light from somewhere
If it's increasing the ISO, that's different from the gain
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Yeah I'm not doubting your tests, just baffled as to why as, like I said to Neil, you're not changing the light entering the camera. Neil might be right and it might be the way the electronics affect the CD AF system, although it's still baffling why it'd do this. Wonder if my Fooj does it too
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Hmmm, good point. I didn't realise that the AF sensors were affected by the sensitivity of the sensor though, I thought it was purely on the amount of light hitting it. Guess they must be influenced by the sensor sensitivity to a small degree then
Yeah I'm not doubting your tests, just baffled as to why as, like I said to Neil, you're not changing the light entering the camera. Neil might be right and it might be the way the electronics affect the CD AF system, although it's still baffling why it'd do this. Wonder if my Fooj does it too
It simulates exposure when you press the shutter button as well as starting the AF, I suppose the AF has to work with the same simulated exposure view..
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Hmmm, good point. I didn't realise that the AF sensors were affected by the sensitivity of the sensor though, I thought it was purely on the amount of light hitting it. Guess they must be influenced by the sensor sensitivity to a small degree then
Increasing the ISO increases the sensors' sensitivity to available light (at the expense of increased noise) so it 'sees' more light.
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Fooj does it as well. I've tried it, I assumed it was down to the contrast focus detection. And although you aren't changing the light entered you are altering it somewhere with it being digital we have to assume it's different to that of cameras of old so there will be a change in there .Yeah I'm not doubting your tests, just baffled as to why as, like I said to Neil, you're not changing the light entering the camera. Neil might be right and it might be the way the electronics affect the CD AF system, although it's still baffling why it'd do this. Wonder if my Fooj does it too
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Not even ye olde cameras invented light and physics ;0)
The exposure triangle is the same whatever you use from a pinhole to an SL. If there's not enough light, you use a faster film or bump up your ISO and a slower shutter speed/wider aperture to capture more light.
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Posted another reply since then, but yes it seems so at least to some degree (the actual light must still play a much larger part I'd have thought otherwise you'd be able to shoot at -5ev
) Every day's a school day
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I go that, but limitations will change. How the camera focus' changes as well. Cameras didn't use to use contrast phase detection to AF.
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Yes, it seems so
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Yeah, all AF film cameras use Phase Detect like DSLRs which uses a dedicated AF sensor to measure the distance to the subject (like a golf rangefinder) and then tells the AF system to focus accordingly.
Like you say, contrast detect relies on light much more hence mirrorless bodies struggling to focus in lower light, unless you use the metering system to make the sensor think it sees more light in the scene. That can only do so much to help though because the light level itself hasn't changed.