Starlight: Varifocal vs Fixed

[Fastb]

The varifocal Starlight can be adjusted from 2.7mm to 12mm
The non-varifocal Starlight is available in 2.8mm, 3.6mm or 6mm, depending on model (if my checking is correct)
The Varifocal's motorized lens increases the price, naturally.
The adjustability is "worth it", some would argue.

But what if someone uses a Varifocal, and dials in the optimal FOV, only to be using the equivalent of 2.8, 3.6 or 6mm lens?

Here's the idea for someone who is considering multiple cameras:
- Buy a single varifocal
- Temporarily mount it where all the multiple cameras would be mounted later.
- Dial in the FOV for each cam location.
- Determine (somehow) what the lens setting actually is, per cam location.
---- Some locations might be happy with 3.6mm
- With this info, don't buy Varifocal for some locations. Instead, buy a cheaper 3.6mm fixed focus. Or 2.8mm, or 6mm.

Q: In other words, can a Varifocal be used as a "lens selector"?

Granted, the varifocal is infinitely adjustable between 2.7mm and 12mm. But in some camera locations, a standard fixed lens might be close enough to the "sweet spot". And it saves money.
Imagine if you spent the money on a Varifocal, only to find they dialed it in to a standard sized lens?

One rebuttal to the above may be:
Newbies often mistakenly go for for wide FOV, thinking "more is better". Then after an incident occurs, they realize they didn't capture a detailed image. With a Varifocal, they could simply adjust the FOV instead of replacing the cam.
- ie: A Varifocal can "future proof" a situation, because when the newbie gets up the learning curve in the future, the lens can be adjusted.
Q: Is that future flexibility worth the higher price of Varifocal?

Curious minds want to know!

Fastb

 

[nayr]

I put a fixed lens against a varifocal, put all the settings the exactly the same.. turned off IR and this was the result:

Fixed 3.6mm @ F2.0:

Varifocal 3.6mm @ F1.4:

The varifocal offers an aperture over 2x as large as the fixed, which results in many more photons making it to the sensor; pay the extra +$35 and buy the Varifocal even if you dont think you need it.

Better Optics all around results in better performance.. This has to be the 50th+ time Ive pointed this out.

 

[Fastb]

Better Optics all around results in better performance.. This has to be the 50th+ time Ive pointed this out.

Fair enough. I didn't spell out one assumption of mine.

I assumed the Starlight architecture (sensor, aperture, electronics, etc) would be rolled out to non-varifocal camera versions.
The Starlight architecture started on higher end models. The "Ultra". Varifocal Turret. Followed later with Varifocal Bullet.

My unspoken assumption is this technology will filter down to more basic models. We see that with autos all the time (ABS, traction control, and soon - auto-pilot)

Maybe the answer to my previous post is;
- 1.4 aperture will never be used with a fixed lens
- Sure, my Starlight Varifocal Bullet (Andy shipped it Friday) is $180. Sure, that's more expensive than a lot of cams. But the so-called "premium" for Varifocal's motorized lens is only $35 or so. Not really a "premium" at all....
- Or the answer might be: "Hey Fastb, enough with the 'Analysis Paralysis' already!"

Fastb

 

[nayr]

All dahua's fixed lens cameras are F2.0 and have been for years.. the reason these Starlights are affordable is because they went with a traditional sensor size that was a drop in replacement for what was out there.. the big sensor cameras are expensive because the optics are not mass produced on the cheap.

Fixed lenses and Varifocal Lenses use different board mounting solutions, go search AliExpress for F2.0 M12, then search for F1.4 M12 and you'll notice basically all the fixed lenses disappear from the search results and everything is a varifocal... Now search for M12 1/1.9 (Big Sensor), hot shit the only lens is ~$100, what happened to the $6 ones..

the big sensor cameras are expensive, and will remain that way unless there is a fundamental shift from 1/3" size sensors to 1/2" size sensors for everything.. I cant really see that happening soon, mebe gradually but it'd take time.. its gonna keep anything 4K w/decent results pricy for a while.

Analysis Paralysis is apt.. You can drain your bank account fast getting into high end optics, just look at what big sensor lenses for DLSR's cost.

 

[nayr]

Also, The F2.0 is ideal for fixed lens cameras.. there is a mathematical reason why fixed cameras use it

You can focus a F2.0 to infinity for 12mm just as easy as 2.8mm.. but when you go to a F1.4 the hyper-focal point shrinks, objects in distance or too close can appear out of focus.. achieving infinite focus gets harder as you get longer lenses and larger apertures, eventually you just cant do it.

So one reason your not going to see F1.4 Fixed Lenses because then people would have to take the camera apart and tweak with focus to be happy.. thats why they are all varifocal so they can be adjusted to whats required.

Read: Hyperfocal distance - Wikipedia and Depth of field - Wikipedia

 

[Fastb]

nayr,

Thanks for the explanation. And links to technical articles. As always, your replies are helpful! Much appreciated.

My light bulb clicked on when you brought Depth Of Field into the explanation. Reminded me of using DOF in photography. Blurred near or far scenery could be used, deliberately, for helping compose a picture. Beneficial to photography, but not so beneficial for security. Likewise, a small aperture (which required a slower shutter speed) could blur moving objects.

Now with my "light bulb" lit, I realize my original post was hare-brained. It's as silly as a photo camera with adjustable aperture, but with no way to focus on the near, medium or far object. Unless it's acceptable to use tools to remove your photo camera's cover for focusing on the subject. LOL. More like ROTFLMAO

nayr, keep telling it as you see it.

Fastb
Dealing with my Analysis Paralysis gene, which infects many Engineers...