In this case, I'm asking about two features. First, image stabilization in the lens. I can understand how software and storage in the camera body might do it. I can't understand how the lens can contribute anything.
Second, focus detection. I can understand how interpretive software in the camera body might judge focus, but how can the lens contribute anything? I have a nominally autofocusing Tamron lens which I use on a Nikon F5-II but with the FTZ converter. So there is no mechanism to make the lens focus. My non-CPU lenses are fully manual. The newer Tamron doesn't auto-focus but the viewfinder does have a display that indicates when it is in focus. Since the older lenses don't do that I assume there must be some feature in the lens. Okay, so maybe it is just that the camera is sending a signal to the lens and the lens sends it back with an acknowledgement of some sort, an electrical signal that the older lenses can't do. How else would the lens contribute anything?
As you can see in this video, the lens is moving around. That leads me to believe that linking some type of gyroscope to the lens's IS/VR/OIS system allows the lens to to point beams of light at the same place on the sensor to the greatest extent possible.
RE: Lens:
The EF mount replaces its predecessor, the FD mount. The standard autofocus lens mounting technology of the time used a motor in the camera body to drive the mechanics of the focus helicoid in the lens by using a transfer lever. The key innovation of the EF series was to use a motor inside the lens itself for focusing. This allowed for autofocusing lenses which did not require mechanical levers in the mount mechanism, only electrical contacts to supply power and instructions to the lens motor. The motors were designed for the particular lens they were installed in. Via Wikipedia Canon EF article.
So in many modern lenses, the battery from the camera powers the lens' function, including autofocus.
As you can see in this video, the lens is moving around. That leads me to believe that linking some type of gyroscope to the lens's IS/VR/OIS system allows the lens to to point beams of light at the same place on the sensor to the greatest extent possible.
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So in many modern lenses, the battery from the camera powers the lens' function, including autofocus.
Thanks. Several thoughts come to mind after seeing that video.
Of course it is obvious that the camera's battery would power all that. Also somewhat obvious is that it must be able to react as fast as the hand motion it is trying to correct. Probably there are limits to what it can do, not being fast enough for some vibration. It wouldn't necessarily need an internal gyroscope, but rather, an algorithm in the body that tracks image content and feeds a signal to the lens to drive positioning motors..
VR in a lens mean considerably more complexity. That makes it more expensive to produce and a bit heavier and larger than just that same glass would require. It would run down the battery charge faster. Over the long haul it would seem more susceptible to wearing out or to losing precision in its positioning.
The value would be that it makes IBIS easier for the camera's firmware. Since it is reactionary, maybe with some limited predictive ability in the firmware, it could help by itself but not be a perfect solution on its own.
So they actually move the lens around, huh? Whoodathunkint? (I'm shooting with vintage lenses on a new mirrorless camera body, so none of the fancy lens mechanism stuff applies. My 70's lenses work just fine, thank you. Provided my technique is good enough, of course. And as a bonus my battery should last longer.)
If you really want to dig into this, your questions are prime candidates for some googling… or even an exchange with one of the AI tools. I’d start with:
“How does autofocus work?” and “How does image stabilization work?”
gdanmitchell wrote:
If you really want to dig into this, your questions are prime candidates for some googling…
Thanks for the recommendations but I would prefer to read a reply from the erudite folks on FredMiranda than read an AI-generated response from Google. FWIW, I have already learned from a forum member's post what I was hoping to learn.
jimmuller wrote:
Thanks for the recommendations but I would prefer to read a reply from the erudite folks on FredMiranda than read an AI-generated response from Google. FWIW, I have already learned from a forum member's post what I was hoping to learn.
An answer to your question is pretty involved, and many of the links you'll get on the search pages from Google take you to excellent explanations written by very knowledgable human beings, some of them the same sources we might use to provide a full answer to your question here.
(Yes, there is an AI summary at the top of Google search pages, but below that you get links to a large set of more complete sources.)
Ion particular, a description of how AF works is somewhat complicated. There are multiple systems in use that (usually) state with contrast or phase recognition systems but when then interpret that and apply it in various ways. these days, those "various ways" can be quite diverse — subject recognition, sticky or not, single shot or continuous, etc.
IS systems either move lens elements (lens IS) or the sensor (IBIS) to counteract movement in the camera/lens system.
gdanmitchell wrote:
An answer to your question is pretty involved, and many of the links you'll get on the search pages from Google take you to excellent explanations written by very knowledgable human beings, some of them the same sources we might use to provide a full answer to your question here.
(Yes, there is an AI summary at the top of Google search pages, but below that you get links to a large set of more complete sources.)
Thank you for the reply. I have learned what I wanted to know. The details of whatever algorithms are used by various manufacturers are interesting for whoever might be working in that field but that wasn't why I was asking. Anyway, thanks again.
