I've seen charts or at least static target photos used with CCTV and I know how difficult it can be to focus cameras using a general scene. I tried to refocus my mobius using the live stream and a laptop and found getting the focus exactly correct to be very difficult.
Not quite sure why you'd want to set 100 feet as the hyperfocal distance. Whilst it might be the theoretical hyperfocal distance, it will compromise the sharpness of near objects a little as everything from 1/2 the hyperfocal distance to infinity is sharp, so that's 50 feet with a 100ft hypefocal . Given that most people probably want maximium sharpness maybe 10-15 feet from the bonnet, or 20 feet overall, would it not make more sense to set it using the double the distance method ie 30-40 feet away? Yes the very far distance will lose a little detail. However, I'm sure most people would rather have razor sharp close in plates than a compromise on close in sharpness to provide a razor sharp sign 200 feet away down the road.
Well, first off, I never said anything about setting the hyperfocal distance at 100 feet, so kindly refrain from putting words in my mouth. With this new lens, so far I often focus on a tree about 100 feet from my window and bring the depth of focus backwards towards the near field until I find the apparent optimal point of focus but occasionally on other nearer objects. Unlike my other varifocal lens, this one seems happier (and easier) when focused farther away because of its greater depth of field. The other varifocal seems to like being focused on objects closer in to achieve the desired results.
You know, it's always rather tedious when you engage in one of these pointless circular arguments where you try to demonstrate how knowledgeable you are about all things optical but then end up showing us quite the opposite. Somehow, I'm not the least surprised to hear you admit to having so much difficulty focusing your Mobius and especially that you find it difficult to, “
focus cameras using a general scene”. Perhaps your eyesight is very poor or maybe you just don't know quite how to go about it?
One of the things that so often comes across with all of your commentary, lecturing and handing out advice along coupled with all the table pounding about how pricey high end, high resolution rectilinear lenses should be used on dash cams is that you appear to have no little or no actual hands-on experience with any of these things you talk about all the time. From all appearances, with the exception of the now destroyed Mobius you've had such a disastrous self inflicted experience with, you don't appear to own
any aftermarket M12 lenses of
any quality or even a suitable camera to put one so how would you know what it is like to do this, especially with a varifocal?
Had you been out here working with, testing, experimenting with and learning about the individual characteristics of various alternative aftermarket lenses the way
@TonyM,
@Harsh,
@dirkzelf ,
@kamkar1,
@jackalopephoto , me and quite a growing list of others here on DCT have been doing for some time now, you just might have a better idea of what you are talking about from a practical, experiential perspective. Where all of us have been actively discussing and posting many examples of our work, you seem to have absolutely nothing to show for yourself except opinions. It all comes across as armchair posing from a distinctly vicarious perspective. If you really want to hand out advice, why not show us first hand what you are talking about and what you can achieve rather than simply parrot things you appear to have read about or seen on the internet?
This notion of using a large static CCTV focusing chart as you have repeatedly advised here in this thread is about as impractical an idea as I can imagine, plus of course, you'd need to go out and spend the money to obtain one of those things. If you had any real world experience focusing a varifocal lens for use on a dash cam you might realize just how much of a fool's errand that would be. You'd turn a simple focusing procedure that takes a few moments into a long tedious affair of setting up the chart and moving it repeatedly to different locations when you eventually discover it wasn't quite in what you thought was the optimal spot to begin with, all the while racing back to your camera each and every time to check focus. Oh, then you'd need to put the whole set-up away until the next time. And if you somehow discovered while driving around that the point of focus you chose wasn't quite what you were expecting you'd have to go back and set everything up again.
Unlike you, I don't find it too difficult to
“focus cameras using a general scene”. I simply point the camera out the window at a nearby tree or shrub and focus on the bark, leaves or branches which serve as excellent “focusing charts”.
Kindly take another look at the various images I posted the other day in this thread. Are those sharp enough for you?? Are the nearby plate numbers distinct and is the rest of the scene clearly defined? Do you really think I require or want your tutoring about how to go about focusing one of these lenses?
What you obviously don't know is that while varifocal lenses can be quick and easy to zoom and focus, using them on a dash cam can be especially challenging and even a bit exasperating at times. These are
fixed aperture variable focal length lenses that were specifically designed for use on static surveillance cameras. They were never designed with the dynamic environment of a dash cam inside a moving vehicle in traffic in mind.
Let me state that again: These are manually operated FIXED APERTURE zoom lenses. While there are many auto iris adjusting zoom lenses on the market, including some CCTV lenses these manual lenses have only a fixed aperture. That means that every time you vary the focal length of this lens, each degree of zoom you choose will change the amount of depth of field you have available to you because the fixed aperture size becomes a relative one according to the focal length. This can make it very challenging and occasionally even exasperating to achieve the desired focus and optimal hyperfocal distance. If you change the focal length by zooming the lens, even a modest amount and then go to focus on the same object at the same distance as you did previously, you are likely to find that the depth of focus has changed to a position you didn't quite anticipate. You'll now need to find a different focus point to keep the hyperfocal distance within the desired parameters.
All in all, I'm finding this 6-22mm ƒ/1.6 varifocal lens to be vastly easier and more forgiving to focus for dash cam use than the 2.8mm-12mm ƒ/1.4 variofocal lens which can sometime be difficult to get “tuned-in”the way I like it. Generally speaking this new lens has a far greater depth of field at all focal lengths but it can also still offer unexpected results at times. The trick is always to move the depth of field in and out until you find that sweet spot where cars directly in front of you are clearly in focus but objects in the mid and farther distance are as well.
Just the other day, not long after posting those beautifully sharp screen shots I did some further macro experimentation with the 6-22mm. Then later I set the camera back to a focal length somewhere in the middle of the range and focused on the same tree out my window I used last time. After that I made a quick trip into town only to discover when I got home and looked at the footage that cars right in front of me where in very sharp focus but cars out in the mid distance where quite out of focus, much more than I might have expected. It seems that the focal length I had chosen to zoom at was different enough from the focal length I chose last time to give me entirely different depth of field results when focusing on the same tree I had previously despite what I thought I saw on my screen.
Only actual hands on experience with different lenses will teach you these things. For example, many of us who experimented with the fast ƒ/1.2 Treeye Starlight lenses reported that they can be a real bear to focus properly due to their shallow depth of field. As I gain experience with this new varifocal lens I'm learning its strengths and weaknesses and discovering how best to optimize my experience with it.
And when I discover the exact focal length I prefer when using this varifocal as a dash cam lens I think I'll probably mark the lens barrel so that I can easily return to that setting. From my experience, sometimes focusing a varifocal for dash cam use can be somewhat of an artform but eventually you figure out how to turn it into more of a science once you get a feel for its idiosyncrasies. Either way, it's certainly annoying to listen to someone who has not spent any time at all learning what to expect from these aftermarket lenses explaining to us how it should be done.