Mobius Telephoto Dashcam

[Dashmellow]

Yeah, it's what I guess you'd call, "Up close and personal!"

Using a telephoto lens this way is very interesting actually, but the problem I think is that if anything should ever happen that you have to report to the authorities, you might find yourself having to explain to someone who doesn't quite understand telephoto video capture in dash cams that, "Officer , (or Your Honor ), I know it looks like it, but I really wasn't THAT close to the victim, you just gotta' believe me!"

 

[SawMaster]

That's why you need a regular cam too. Though it might be to our advantage to have only a telephoto cam in the rear to exxagerate any tailgaters Now I need 8 cams in my van to achieve good coverage. Will you people stop coming up with these ideas so I can eat instead of buying more dashcams?

Phil

 

[Dashmellow]

I came to a stop to let this lady back out of a parking space. I was probably a good 20-25 feet away from her but from the looks of the telephoto dash cam capture I appear to be right on top of her vehicle. As much as I enjoy having a telephoto dash cam I definitely would never have it as my only camera, front or rear.

 

[Rocketvapor]

Telephoto makes it look like you almost hit the car, wide angle makes it look like you had plenty of room to avoid the wreck.
Dang, just can't win

 

[Dashmellow]

Telephoto makes it look like you almost hit the car, wide angle makes it look like you had plenty of room to avoid the wreck.
Dang, just can't win

Having both wide and tele together works pretty well though.

 

[Harsh]

What focal length on these 1/2.5 - 1/3 sensors/lenses would be would be equivalent to what we see?

Edit - Not including peripheral vision.

 

[Dashmellow]

There's no way to know exactly. Maybe somewhere around 12mm although the difference between the default circle of coverage of the lens vs the actual size of the sensor plus the fact that there are no calibrations on the zoom make it all guess work. Anyway, as I mentioned a while back there seem to be visual similarities to your fixed focal length 12mm examples and the magification I have set on the varifocal.

As for what we actually see, somewhere I read that a 50mm lens on a 35mm camera is supposed to be close to human vision.

 

[Harsh]

As for what we actually see, somewhere I read that a 50mm lens on a 35mm camera is supposed to be close to human vision.

How many mm would it equate to on the M1. Sorry, I get confused with these crop factor calculations.

 

[Dashmellow]

How many mm would it equate to on the M1. Sorry, I get confused with these crop factor calculations.

I dunno, I need to think about that. Maybe the "A" lens comes closest at 2.5mm......or a little wider than that?

 

[Harsh]

If the crop factor is 7.21, so 50/7.21 is 6.9.

 

[Rocketvapor]

How many horizontal degrees do you get with ONE EYE?

 

[SawMaster]

How many horizontal degrees do you get with ONE EYE?

.

Less than what you need?

The numbers and specs still confuse me some, but I am learning something here which is good. And with the links and great explanations, anyone who wishes to try this can now do so very easily. I'll be along when my finances allow which I hope is soon, but I may need a new Möbius or at least the PCB first, plus another cam for the front of the minivan when I get it going again. And maybe some cards as half of mine have reached or passed their expected life but are still working 100% at last testing.

A hearty round of applause to you guys who are leading the way here
Phil

 

[c4rc4m]

The numbers probably still confuse the pro's. As Dashmallow said, the commonly accepted figure is 50mm lens equivalent @ 35mm film size (full frame) ie. with a 36mm x 24mm sensor. That's a 39 degree fov according to Canon's website. Personally, I've never been convinced because the human eye is very much the sum of the central vision and the periphery and the brain controls how much you see. My opinion is the human eye is much wider than 39 degrees. If I sit at my desk and take the focus off my central vision, I reckon I can see more like 90-120 degrees with a single eye, with the brain then narrowing down the field when you're doing something specific eg typing on your keyboard, according to what you're doing / concentrating on.

For our purposes, what the eye sees doesn't matter so much as what the camera sees. To that end, the best way to find the best compromise is experimentation plus the prior experience of others, or a wide zoom lens and finding the perfect setting and then back calculating the prime equivalent. For any application there's almost certainly going to be a range of fov's that different people like, and also a range dependant on whether there's a 2nd telephoto in play.

 

[Dashmellow]

The numbers probably still confuse the pro's. As Dashmallow said, the commonly accepted figure is 50mm lens equivalent @ 35mm film size (full frame) ie. with a 36mm x 24mm sensor. That's a 39 degree fov according to Canon's website. Personally, I've never been convinced because the human eye is very much the sum of the central vision and the periphery and the brain controls how much you see. My opinion is the human eye is much wider than 39 degrees. If I sit at my desk and take the focus off my central vision, I reckon I can see more like 90-120 degrees with a single eye, with the brain then narrowing down the field when you're doing something specific eg typing on your keyboard, according to what you're doing / concentrating on.

For our purposes, what the eye sees doesn't matter so much as what the camera sees. To that end, the best way to find the best compromise is experimentation plus the prior experience of others, or a wide zoom lens and finding the perfect setting and then back calculating the prime equivalent. For any application there's almost certainly going to be a range of fov's that different people like, and also a range dependant on whether there's a 2nd telephoto in play.

Keep in mind that the 50mm lens/35mm full frame camera human vision analogy is only an approximate correlation. Our eyes are not camera systems and the retina in the eyeball is a curved surface unlike the flat surface of a film plane. The basic reason that a 50mm lens is often referred to as a "normal" lens is not just due to its approximated FOV but also the general impression of magnification of a scene in the real world. There is also a difference between the FOV our eyes can observe and the perception of vision along with each person's unique facial anatomy such as the size and shape of the nose, shape and angle of the brow, etc.

Apparently, the focal length of the human eyeball is about 22-24mm with an aperture of ƒ/3.5 if you calculate using the physical refraction of the eyeball and a pupil diameter of 8mm or 17mm focal length with an aperture of ƒ/2.1 using the optometric diopter value. See THIS article, "The Camera Versus the Human Eye" at PetaPixel for a fascinating discussion on the subject.

 

[Harsh]

Borrowing from Tony's CPL DIY for the Varifocal, made a CPL for my front facing 12mm.

24mm CPL (Mini series), lens cap that came with one of the telphoto lenses (don't remember which one). Number 3 printed on the inside of the lens cap, searched online but the number doesn't seem to be of any significance. It's an 11mm cap made of hard plastic.



Removed the front plastic using a detail knife and glued the plastic ring in the centre of the glass with UV glue. Filled the entire circular space between the CPL's inner rim and the lens cap with glue, don't see it falling off.





Made one for the Maxi as well but there's major vignetting. May work with the A lens.







Aligned the CPL and applied two cutouts of masking tape, one on the lens's rim and one on the cap. Lack of a screen makes it necessary.



Mounted



Screenshots from the Android app (1280x720)

Before



After

 

[kamkar]

I feel the 8 mm i used are more true to what i see with my own eyes, but i like the extra range of the 12 mm, and after all its for what go on out ahead and not really for anything related to me in my car, that i leave for the conventional lens camera.

I think for the rear i will be going for a 6 mm lens maybe 4 mm.

 

[Harsh]

I feel the 8 mm i used are more true to what i see with my own eyes, but i like the extra range of the 12 mm, and after all its for what go on out ahead and not really for anything related to me in my car, that i leave for the conventional lens camera.

I think for the rear i will be going for a 6 mm lens maybe 4 mm.

My order for a 6mm 5MP from Fulekan should be here soon, I'll be trying that for the rear.

 

[TonyM]

My order for a 6mm 5MP from Fulekan should be here soon, I'll be trying that for the rear.

How many telephoto lenses have you got now?
Since changing to a varifocal lens both front (6-22mm) and back (2.8-12mm) I admit I'm less excited by the fixed focal length telephoto lenses. However I do realise that typically there are benefits such as a wider aperture and smaller physical size with a fixed lens.

 

[Harsh]

How many telephoto lenses have you got now?
Since changing to a varifocal lens both front (6-22mm) and back (2.8-12mm) I admit I'm less excited by the fixed focal length telephoto lenses. However I do realise that typically there are benefits such as a wider aperture and smaller physical size with a fixed lens.

A few. Have two 8mm and two 12mm 3MP lenses that aren't in use anymore. Then the 5MP 8 and 12mm that are currently in use. Have another set of the 5MP 8 and 12 coming with the 6mm, didn't want to pull the ones attached to the M1 for the pre-production A129.

I prefer these to the Varifocals, mainly because of the size.

 

[Harsh]

Extension rings arrived a couple of days back, waiting for the new set of lenses.