Viofo Telephoto Dash Camera Add On

[Dashmellow]

I would send you mine if you have an A229pro or plus to test with it?

Thanks for the nice offer Ben! I've been up in the air about what's going to happen with my apparently defective A119 Mini 2 so I've been reevaluating what to do and Prime Day is coming up so, let's see how it all goes. Again. thanks!

 

[SafeDriveSolutions]

Thanks for the nice offer Ben! I've been up in the air about what's going to happen with my apparently defective A119 Mini 2 so I've been reevaluating what to do and Prime Day is coming up so, let's see how it all goes. Again. thanks!

I want to know how it does to the mobius…

 

[Dashmellow]

I want to know how it does to the mobius…

Do you mean how it compares?

The image in THIS POST is from a 1080p Mobius if that helps at all.

 

[SafeDriveSolutions]

Do you mean how it compares?

The image in THIS POST is from a 1080p Mobius if that helps at all.

where do i get one of those Mobius to test against the telephoto Viofo. I would love to prove that the 1080p telephoto would have been good enough

 

[Karagandinez]

Would you mind elaborating on the differences you're seeing? I can swap rear/telephotos on the Plus and Pro while I test them together if you've been noticing differences between connected models.

At the moment I can’t say anything, I have to check everything myself, but unfortunately it won’t work out quickly...
At first glance, the camera with a telephoto lens has slightly worse video quality when working with the A229 Plus.

 

[Karagandinez]

Here are my reasons why a good rear cam is important:

• In general - there could be cases when collision with oncoming vehicle happens in tight turn, when the plate of the car would not be visible for telephoto, or tight oncoming traffic when the car at fault could be blocked by another car in front of it, at the range where telephoto is best focused.

- In this case, a good rear camera may be able to capture the plate from behind (last hope).

Did I write somewhere that I am against the rear camera?
I always use a normal rear window dash cam. I like it better when the front and back are independent of each other.

 

[TonyM]

I'm looking through some sample footage from this morning and I'm seeing a surprising amount of blockiness / compression in the telephoto video, even at the max bitrate. It seems to be more evident when there's a lot of motion across the frame like when I'm driving through tree-filled backroads vs. driving on a more open highway. Looking at some oncoming plates, yeah even the telephoto is struggling.

What is the max bitrate on the RTC300?

I'm not sure if the telephoto would behave differently on the Plus vs the Pro.

Different processor / firmware? Different bitrate?

 

[Augustus]

I struggled deciding how I was going to mount my (2) telephoto cameras, (front & rear).
I finally decided to mount them exactly in the middle at the top of the front & rear windows to split the difference.
I'm glad I did because I can still get oncoming cars, and cars to the right when I'm on the highway in the "center" lane.

As far as horizon line adjustment.
I first tried 50/50 and that did not work very well.
I took Viofo's (Alex's) Instructions and adjusted 60 road / 40 sky and it provided much better results.

I've been meaning to to adjust the telephoto on the front window to look out the back window to see how it would perform in applications like Miata, Porsche, Corvette, or other cars that do not have a rear window to mount a traditional "rear" camera.
One thing I'm not pleased with about my telephotos is they seem to be only "in focus" at 20 Meters.
Everything beyond 20 Meters is blurry.
I reported this to Viofo, and I was told it's just the way the lenses are optimized & adjusted.
I don't know anything about lenses in the first place, but my Sony Action Cam is in focus from 20cm to infinity.

Also getting the angle just right is why I use those standard 1/4 camera ball mounts to get all those wacky angles for interior, and left & right side cameras.
I just have to drill a 1/4 hole in the removable bottom plate under the 3M sticky pad.
It's more labor to drill the hole, but easier later on swapping cameras in / out instead of using a new adhesive each time.

I just got a new 43" 4K Samsung Monitor, and I'm chomping at the bit to gather some new test footage with the new updated firmwares.
I'm ashamed to admit but before I got this new 4K monitor I was using a 32" 720p monitor from 2010 to review all my dash cam footage. lol
I also reconfigured my camera set up slightly.

Thanks for these tips Chuck. I just got my telephoto today and wondering where the heck to mount it because the A229 Pro interior camera is at the top middle of my windshield :/. Also was curious about 50/50 alignment or whatever other way to do it, because it is zoomed in being a telephoto and all ...

 

[Nigel]

One thing I'm not pleased with about my telephotos is they seem to be only "in focus" at 20 Meters.
Everything beyond 20 Meters is blurry.
I reported this to Viofo, and I was told it's just the way the lenses are optimized & adjusted.
I don't know anything about lenses in the first place, but my Sony Action Cam is in focus from 20cm to infinity.

Wide angle action camera lenses have a much bigger depth of field than you can get with a telephoto, restricted by physics, but normally even an action camera won't focus properly closer than about 80cm. Possibly your Sony had autofocus?

There is no need for a telephoto dashcam to focus perfectly beyond license plate reading range, so given that the depth of field is restricted, I would expect them to look a little soft closer than 5m and beyond about 40m, if the focusing is perfect, which is unlikely. it will probably be either a little closer or a little further than those figures. The distance should be soft rather than blurry, and at less than 5m it is reasonable for a telephoto to go blurry.

Having looked at some of your images, the focus seems pretty sharp between 5m and 40m, but I noticed that the images (frame grabs) that you post are not so sharp, I suspect that maybe you are zooming in too far and the zoom is making them blurry, or maybe you are viewing the 2K images on your 4K monitor and comparing them to 4K images, which should have twice the detail due to extra resolution and extra bitrate. Also, remember that when you post high resolution images to this website, they get converted to lower resolution.

If you have a blurry example, that is not caused by motion blur, post it up and we will have a look...

 

[Dashmellow]

The distance should be soft rather than blurry, and at less than 5m it is reasonable for a telephoto to go blurry.

As always Nigel, you speak with authority explaining to us what people should and shouldn't expect from telephoto lenses on dash cams even though you have no personal experience with them. The fact is the depth of field can vary due to a number of factors, such as lens design, hyper-focal distance and aperture.

I don't have a lot of time right now because of work so I merely grabbed a convenient (but not the best) example from an archive, but here is an example of a telephoto image where I am parked nose to nose with another vehicle in a parking lot with a telephoto lens - far closer than the 5 meters you claim should be blurry, yet it is tack sharp. Note too that even the Tesla charging stations in the distance on the left side of the image are relatively sharp and in focus.

I may elaborate on other points made in Nigel's post later in the day if I have some time.

Don't listen to Nigel, folks. He knows not of which he speaks.

1080P

 

[Karagandinez]

What is the max bitrate on the RTC300?

On my cameras with a telephoto lens on firmware V1.3_240605 the Bitrate is 24.0 Mb/s

 

[Karagandinez]

1080P

Your image is so clear.
Perhaps there is something wrong with my lens...

Although if you look at the wall everything seems fine.

 

[Nigel]

here is an example of a telephoto image where I am parked nose to nose with another vehicle in a parking lot with a telephoto lens - far closer than the 5 meters you claim should be blurry, yet it is tack sharp. Note too that even the Tesla charging stations in the distance on the left side of the image are relatively sharp and in focus.

The trees in the top left far distance are quite blurry in that image, having them blurry allows for a closer focus than if they were sharper.

I would hope that the Viofo RTC300 would be focused so that the far distance is only soft rather than blurry. There is no need to focus sharply at 1 meter, the standard front camera can read any non-motion blurred plate at less than 5 meters.

The fact is the depth of field can vary due to a number of factors, such as lens design, hyper-focal distance and aperture.

Lens design does not affect depth of field, unless you count choosing the focal length and aperture as lens design,
Hyper-focal distance does not affect depth of field.

The only things which affect depth of field in the design of a dashcam are:

1. Focal length,
2. Aperture,
3. Distance at which the lens is focused,
4. Image sensor pixel size.

Some of these values, quite likely all of them, will be different on the Viofo RTC300 than on your telephoto, so the depth of field will be different.

 

[Chuck McCoy]

What is the max bitrate on the RTC300?

Different processor / firmware? Different bitrate?

Yo Tony,
Based on my testing the A229 Pro & A229 Plus Rear cameras are "identical" with the RTC300.
Except the RTC has a zoom lens of course.
-Chuck

 

[Dashmellow]

Hyper-focal distance does not affect depth of field.

Once again Nigel, you don't know what you are talking about.

From Wikipedia: "Hyperfocal distance is a distance from a lens beyond which all objects can be brought into an "acceptable" focus. As the hyperfocal distance is the focus distance giving the maximum depth of field, it is the most desirable distance to set the focus of a fixed-focus camera."

 

[Chuck McCoy]

There is no need for a telephoto dashcam to focus perfectly beyond license plate reading range

Incorrect.
Everything in frame should be in focus just like my eyeballs. lol

normally even an action camera won't focus properly closer than about 80cm. Possibly your Sony had autofocus?

I was wrong, the specs say; "Minimum Focus Distance" is 30cm.
It does not say 20cm to infinity.
However, everything in frame is in focus, even things far away in the background;

https://www.sony.com/electronics/support/action-cam-hdr-as-series/hdr-as200v/specifications

 

[Nigel]

However, everything in frame is in focus, even things far away in the background;

Using an F2.8 aperture lens helps quite a lot with focus, although not with low light, and then only being FHD helps some more. These are not equivalent cameras.

 

[Nigel]

Once again Nigel, you don't know what you are talking about.

From Wikipedia: "Hyperfocal distance is a distance from a lens beyond which all objects can be brought into an "acceptable" focus. As the hyperfocal distance is the focus distance giving the maximum depth of field, it is the most desirable distance to set the focus of a fixed-focus camera."

Shouldn't a dash camera be designed to provide maximum plate readability rather than maximum depth of field? In which case the hyperfocal distance would be irrelevant! With a non-telephoto dashcam, it is normal to focus it at the hyperfocal distance, but this is not always desirable, many fixed focus cameras are focused much closer.

For a telephoto dashcam, the best distance to focus it at is probably at the maximum plate reading distance, since that is the distance at which you need the sharpest image, and thus will give the maximum plate readability. So it would be reasonable to argue that license plate size should affect the focus distance and thus depth of field.

Hyperfocal distance does not affect depth of field, it is just the focus distance at which you get the maximum depth of field, but it is not something you can change on its own, to change it you have to change aperture, focal length, and/or pixel size, which can affect the Depth of field and thus change the Hyperfocal distance, so it is depth of field that affects hyperfocal distance, not hyperfocal distance that affects depth of field!

 

[Dashmellow]

Your image is so clear.
Perhaps there is something wrong with my lens...

View attachment 73146


Although if you look at the wall everything seems fine.

View attachment 73147

You're right, that doesn't look so great. Even the brick wall could be a bit sharper in my opinion.

In the image with the flowers the exposure looks off and it's almost as if the sharpening and other parameters set in the firmware need adjusting. On the other hand is it possible that the flowers and leaves are just quivering in the breeze but the brick wall is solid and fixed? I suggest continuing with your testing for now.

My sample image was done with a 1080p Mobius with a 5 Megepixel ƒ/1.6 varifocal lens, from which I generally get excellent results. The thing with the Mobius platforn and the reason I love it so much is that you configure the camera via a Windows based PC GUI that provides the user with a broad range of advanced photographic controls, options and adjustments unavailable on any other dash cam. When you install an aftermarket lens, especially a telephoto you can tweak the image any way you like and often dramatically improve the IQ beyond the default settings. It is a fantasy, I know, but I would love to see a (pehaps hidden) sub-menu on traditional dash cams that would provide advanced photographic controls to those who know what they are doing and want to tune their camera to their exact imaging preferences.

This example is old and from a different telephoto project but you can see some of the adjustments I've made, especially in increasing the sharpening, contrast and saturation.
The system is based on a traditional 8 bit indexed palette that provides 256 levels of exposure, contrast, color depth, grayscale, etc., so you'll see that you have 128 levels above and 128 levels below normal. (128 x 2 = 256)
8 bit is an older system but it works well here because it offers a lot of precision adjustment without being overly complex.

 

[Dashmellow]

Shouldn't a dash camera be designed to provide maximum plate readability rather than maximum depth of field? In which case the hyperfocal distance would be irrelevant! With a non-telephoto dashcam, it is normal to focus it at the hyperfocal distance, but this is not always desirable, many fixed focus cameras are focused much closer.

For a telephoto dashcam, the best distance to focus it at is probably at the maximum plate reading distance, since that is the distance at which you need the sharpest image, and thus will give the maximum plate readability. So it would be reasonable to argue that license plate size should affect the focus distance and thus depth of field.

Hyperfocal distance does not affect depth of field, it is just the focus distance at which you get the maximum depth of field, but it is not something you can change on its own, to change it you have to change aperture, focal length, and/or pixel size, which can affect the Depth of field and thus change the Hyperfocal distance, so it is depth of field that affects hyperfocal distance, not hyperfocal distance that affects depth of field!

Again, you demonstrate your lack of hands on experience here. As I keep saying, telephoto lenses are NOT just about capturing license plates (even though they do). They are about better capturing and telling the story of your journey in concert with your traditional dash camera.

Your technical notions about things like hyper focal distance seem to all be inside your head but disconnected from how things actually work in the real world. Hyperfocal distance is not just about maximum depth of field but also about where the user (or factory) who focuses the lens wishes to position the hyperfocal distance for the optimal and desired range of acceptable focus.