A139 (Pro) Telephoto Remote Camera

pinoyplaya4life said:
for the A139 remote camera doesn’t need it to be a specific distance so you can achieve focus since the threads on the mount is limited to how far you can adjust it? Otherwise I wouldn’t be able to mount the lens correctly or it wouldn’t mount at all
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That's not what MBF means. You are talking about BFL which is a different concept.
 
Dashmellow said:
That's not what MBF means. You are talking about BFL which is a different concept.
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Hmm. Lens manufacturer seems to use them interchangeably. In either case, the back focus distance is limited to 6mm or shorter and still be able to engage on the threads.

I see cad drawings referring to this distance as MBF on one and then BFL on another; different manufacturer.
 
At the gym rn. I’ll check Tony’s post and see if he has the measurement between the sensor to the end of the mount. If the focal point of the lens is inside the lens, then I can probably get away with it if I can still engage on the threads if BFL is too high. Will have to do some calculations.

I was looking at MBF because most of the lens I see have the glass just sitting at the bottom of the barrel.
 
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pinoyplaya4life said:
Perhaps the mechanical is the limit on how far it can go in. So if BFL is 10mm and MBF is 6mm, then you have a back focus distance of 4mm when you screw it all the way in and can’t go any lower.

Depends on where the optics is placed on the lens I guess
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No. That's not really how this works.

BFL is fixed. That's the thing you need to be concerned with here. MBF is variable actually.

I'll have to follow up with this later or tomorrow though.
 
Okay. Here’s what I gathered from Tony’s post.

The distance from the sensor to the edge of the M12 lens mount is measured at 8.79mm. Let’s assume this is correct even though the sensor has a small thickness.

Tony noted that he was able to achieve focus with the 8mm lens just at the edge of the mount. Barely engaged.

This means the distance from the sensor to the focal point on the lens is as follows:

8.79mm + distance from the focal point of the lens to the back of the lens (the space between the glass to the back of the lens)

The second part can be calculated as BFL minus MBF = 10.02mm - 6.80mm = 3.22mm

Therefore, for that specific lens, the distance from the sensor to the focal point of lens is 8.79mm + 3.22mm = 12.01mm. This number minus the BFL is how far he can engage the lens which would be 12.01 - 10.02 = 1.99mm

Since Tony was not able to achieve focus without modification to the mount, the 1.99mm he had available was probably reduced from the thickness of the sensor plus any little distance the lens was inside the mount but didn’t engage the thread. with all that accounted for, he was able to get “somewhat focus” but didn’t get the lens secured in the mount.

In short, both BFL and MBF plays a factor to figuring out which lens will work given the set parameters you have to work with (without having to modify anything else). You need both, not one or the other. But wait there’s more! see simplified equation below.

On the case of the 6mm lens he initially used, using the same calculation:

BFL: 5.66mm
MBF: 5.01mm

Total Length: 8.79mm + (5.66mm - 5.01mm) = 9.44mm

maximum thread engagement to achieve focus = 9.44mm - BFL = 9.44mm - 5.66mm = 3.78mm. This one is much higher than the 8mm lens which guarantees focus since it allows you enough thread engagement to position the lens properly.


Simplified Equation:

Variables:
MTE = Maximum Thread Engagement
BFL = Back Focal Length
MBF = Mechanical Back Focal Lenth
8.79mm is the measured distance from the edge of the mount to the sensor.

MTE = 8.79mm + BFL - MBF - BFL
MTE = 8.79mm - MBF (eliminated BFL from equation).

This means BFL is no longer relevant!

So why was I looking for a lens with MBF less than 6mm? Because I want it to engage at least 2.79mm to achieve focus. Doesn’t matter what the BFL is.

This problem can be solved in similar fashion as this whereas in that particular case, the height of cat and turtle didn’t matter.

2BCE7863-8B2D-44E2-8E60-437FFCDE3466.jpeg


Does this mean a lens with a BFL of 100m or even 1000mm will work? Yes, as long as the MBF is less than 6mm so you can engage the threads. Then the lens will be positioned to the appropriate BFL.
 
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@pinoyplaya4life, I hardly know what to make of your last two posts. This is some of the most absurd pretzel logic magical thinking I have ever seen on this forum and that's saying something. Virtually none of what you've posted here is accurate or even how any of this works!

You are literally making up terms, concepts and calculations out of thin air!

There is no such thing as "MTE". Each lens has a different length barrel based on its optical formula. Each lens module's threaded barrel has a different depth. Each module is mounted differently in each housing or may have a different flange distance.
Apparently, for you the invention of the technical sounding term "MTE" simply means, "how far can I screw this thing in?"

"MBF" does not mean "Mechanical Back Focal Length", even if you imagine that's what it means. There is no such thing as "Mechanical Back Focal Length", (you can't just arbitrarily stick an "L" on the end of "MBF" and come up with a new meaning.) MBF means "Mechanical Back Focus" and this is different than BFL - " Back Focal length". You don't add the two numbers and subtract the difference. The terms have a relationship but one is fixed while the other can be variable. One is a term having to do with the optical focal point within the lens and is determined by the optical design of the lens elements and the other is the physical position of the surface of the rear glass lens element. Certain lenses such as zoom lenses, cinematography lenses and astrophotography lenses have the ability to change the back focus on the fly but dash cam lenses are very simple and do not. For dash cams and action cams, the only number you need to concern yourself with is BFL - back focal length.

From what I can gather here you seem to have no personal experience modifying cameras with aftermarket lenses or knowledge of optics and yet you offer up what you believe to be definitive explanations about how this all works. It's pretty absurd. I don't really know what else to say.
 
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TonyM said:
All dashcam and action camera lenses I have seen have the IR cut filter attached to the back of the lens.
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A few of the dash cams I've owned have had an IR-cut filter mounted directly over the sensor with a non-IR lens installed. I've had a couple of CCTV cameras like that too. That was quite a while ago so perhaps that is not done anymore?
 
Dashmellow said:
@pinoyplaya4life, I hardly know what to make of your last two posts. This is some of the most absurd pretzel logic magical thinking I have ever seen on this forum and that's saying something. Virtually none of what you've posted here is accurate or even how any of this works!

You are literally making up terms, concepts and calculations out of thin air!

There is no such thing as "MTE". Each lens has a different length barrel based on its optical formula. Each lens module's threaded barrel has a different depth. Each module is mounted differently in each housing or may have a different flange distance.
Apparently, for you the invention of the technical sounding term "MTE" simply means, "how far can I screw this thing in?"

"MBF" does not mean "Mechanical Back Focal Length", even if you imagine that's what it means. There is no such thing as "Mechanical Back Focal Length", (you can't just arbitrarily stick an "L" on the end of "MBF" and come up with a new meaning.) MBF means "Minimum Back Focus" and this is an entirely different optical term that has nothing to do with BFL - " Back Focal length". You can't add the two numbers and subtract the difference to come up with a solution to how far the rer element nees to be from the sensor. MBF has nothing to do with getting the lens to focus in the mount. Back focus works in relationship with the front focus according to how the lens is used. It has little or no concern for dash cam users.

From what I can gather here you seem to have no personal experience modifying cameras with aftermarket lenses or knowledge of optics and yet you offer up what you believe to be definitive explanations about how this all works. It's pretty absurd. I don't really know what else to say.
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I’m pretty sure you’re the one who doesn’t understand it.

Why do you think Tony had to modify the lens holder to achieve focus on the 8mm lens? Because he couldn’t properly place the lens to the right distance to achieve focus and still secure it in place.

He needed to place the lens in a specific distance from the sensor to get proper focus. But because the housing had limited length, he couldn’t thread it in.

A solution to this is to get a lens extender. But using an extender has extra material where you can’t thread the lens to the proper distance. So if he used an extender, there exist a distance where he can’t get to and if that distance is the BFL distance, he wouldn’t be able to get to it and the image he gets would not be properly focused.

Reason why he had to make modifications to the mount.

MTE is a term I used so I didn’t have to type out the Maximum Thread Engagement length for calculating how much threads can engage to position the lens to the correct focal distance. You can’t just put the lens anywhere you like.

It’s clear to me that you’re the one who doesn’t know what he’s talking about.
 
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TonyM said:
The MBF of 6.8mm is only 1.7mm more than the 6mm F1.2 lens I have been using so far, but it was just enough difference that the new lens did not engage the threads of the M12 holder. I had measured the depth of the lens holder at 8.8mm before buying the lens which I thought would be enough, however the sensor has a certain thickness which I did not measure and this turned out to be an oversight on my part.
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Here’s some insight for you and why MBF is critical.
 
Since the sensor has some thickness to it, it reduces the distance from the front of the mount to the sensor.

In my calculation I used 8.79mm. Let’s say the sensor thickness is 1mm (just an example), then the calculated MTE for this specific lens is reduced from 1.99mm to 0.99mm. Now, the threads do not always start at the beginning. So there’s probably some distance from the entrance of the mount to where the thread actually starts and that’s why he was not able to engage the threads.

If you use any lens that has an MBF greater than 8.79mm, it is 100% not going to work.

Note this is specific to this A139 interior lens. Other cameras are designed different so the depth of mount would be different.

6mm MBF and under would be a safe bet. Could be tight but should get you some thread engagement and achieve proper focus.
 
pinoyplaya4life said:
I’m pretty sure you’re the one who doesn’t understand it.

Why do you think Tony had to modify the lens holder to achieve focus on the 8mm lens? Because he didn’t get proper thread engagement.

MTE is a term I used for calculating how much threads he can engage to position the lens to the correct focal distance. You can’t just put the lens anywhere you like.

It’s clear to me that you’re the one who doesn’t know what he’s talking about.
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This is funny! :ROFLMAO:

You literally make sh*t up to prove your point and invent imaginary definitions about terms you don't understand like MBF and somehow I'm the one who doesn't know what I'm talking about? HAH!

As for @TonyM, he had to modify his lens holder because he couldn't otherwise achieve the proper back focal length to sensor distance to achieve focus and this has nothing to do with any of the other fanciful reasons you put forth. Tony is highly skilled and experienced in performing camera modifications and he and I and a number of other long time forum members have been sharing our experiences and knowledge about aftermarket lenses and mods publicly and privately for years. Unfortunately, Tony appears to also be misinformed about the proper definition of MBF and this apparently is the reason you've gone down this unfortunate rabbit hole. MBF is an entirely different optical concept from BFL and has nothing with the measurements you are talking about.

I've been modifying dash cameras on this forum with aftermarket lenses and otherwise for at least eight years now and I was actually the first member on the forum to feature a telephoto lens on a dash cam more than five years ago.

How about showing us some examples what you have accomplished, Mr Expert. ;)
 
Good for you. You do you and I do me then. You achieved something through trial and error. Doesn’t mean you understand how it works.

Anyone can buy a lens and try to see if it works or not, and if it doesn’t, make adjustments.

It takes knowledge to get things right the first time.

I’m still searching for a lens to get mine right the first time. But should post some results here soon.

I’m looking for one either 8mm or 12mm (reasonably priced) but can’t find something that would work without modifying the lens holder
 
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Dashmellow said:
A few of the dash cams I've owned have had an IR-cut filter mounted directly over the sensor with a non-IR lens installed. I've had a couple of CCTV cameras like that too. That was quite a while ago so perhaps that is not done anymore?
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Interesting. I was only speaking from my experience having opened a handful of cameras (Mobius, SG, Viofo). Perhaps other manufacturers do it differently.
 
Dashmellow said:
Unfortunately, Tony appears to also be misinformed about the proper definition of MBF
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I was following the diagrams and terms printed on the Aliexpress listings for the 6mm and 8mm lenses that I bought. They may not be the correct terminology - tbh I did not check :unsure:

Irrespective of the name, I was interested in the distance between the sensor and the back end of the M12 thread, when the lens is in correct focus.
 
pinoyplaya4life said:
Good for you. You do you and I do me then. You achieved something through trial and error. Doesn’t mean you understand how it works.

Anyone can buy a lens and try to see if it works or not, and if it doesn’t, make adjustments.

It takes knowledge to get things right the first time.

I’m still searching for a lens to get mine right the first time. But should post some results here soon.

I’m looking for one either 8mm or 12mm (reasonably priced) but can’t find something that would work without modifying the lens holder
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How would you know whether any of the lens conversion mods I've done were trial and error?

Why did you think Tony and me and most of the other members who've been doing lens mods even know these terms?

At least you've answered my question about whether you've ever done a lens mod on a camera before. Apparently not. And you should get some hands-on experience under your belt before spouting misinformation as fact. From what you've had to say so far there is much you don't know as there are important considerations you've left out.
 
lol mister experience. Where has your experience gotten you? For someone with your so called “experience” you would think one would have already started their own company and put their experience to work. Yet you’re still here doing trial and error.
 
If you’ve been working on telephoto mods for 7 years, then you’re doing something wrong. Should have been a one time thing and never looked back. Clearly you’ve got unresolved problems that you’ve spent so much time experimenting.
 
pinoyplaya4life said:
If you’ve been working on telephoto mods for 7 years, then you’re doing something wrong. Should have been a one time thing and never looked back. Clearly you’ve got unresolved problems that you’ve spent so much time experimenting.
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What? You've got to be kidding!

I've modified numerous cameras with various lens (and other) mods over the years, not all of them with telephotos. Cameras made seven or eight years ago are now obsolete, except for perhaps the Mobius.

These attempts at petty insults are really pretty laughable and only serve to further reveal your ignorance.
 
Dashmellow said:
What? You've got to be kidding!

I've modified numerous cameras with various lens (and other) mods over the years, not all of them with telephotos. Cameras made seven or eight years ago are now obsolete, except for perhaps the Mobius.

These attempts at petty insults are really pretty laughable and only serve to further reveal your ignorance.
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keep telling yourself that.
 
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