A Major Flaw in Long Lenses and PTZs Found

Linear density is determined by the lens aperture.
Was convinced.

A Fujinon 8-80mm varifocal lens with a 720p Samsung SNB-5004 camera

Was the Samsung actually tested at 720p?

It's native resolution is 1280x1024, and since your ppf is based on horizontal pixels, you could pick up 50% more vertical pixels by using 1024, without affecting the ppf calc at all.  

Would be interesting to see the same test with a Canon ES lens which is a DSLR lens that appears to have better glass than traditional lenses. I believe the Avigilon Pro Series cameras have the Canon ES lens for the 8, 12, 16 & 29 MP have the Canon ES lens.

Hi Ethan, thank you for your excellent article. By any chance do you have a long, fixed lens which could be used to compare the quality of image against the varifocal lens on the Samsung SNB-5004?

Can you say at what length of lens, and below, image degradation becomes a non-issue? Does this vary much depending upon the brand of lens or other factors? Thank you for your information.

Isn't the reduced quality due to anisoplanaticism across the image? The angular size of the pixels in these examples is 5 seconds of arc or thereabout. So one can expect atmospheric image warp to start to become a problem. Also in the movie (although there for illustrating depth of field issues), I think I see warping of the edge of the cones. I also think warp can be seen in the eyechart. Look at the "z" in the top line. I think warping is also present in some of the face images. If the focal lengths were doubled, or the pixels made smaller, then I think that this would become a huge problem. So I don't think there is anything wrong at all with the lenses.

As an integrator many of the discussion points regarding anisoplanaticism and isoplanaticisim made my head ache but the insight is invaluable. Especially when one comment / recommendation stands out so clearly: "the effect goes away very significantly if you get the camera off the ground." Thank you Rick!

The second critical reminder is the truism that the image is only as good as the glass in front of the camera. We routinely shot surveillance photos of investigative targets 200-400 yards away and learned even the best 35mm cameras and finest grain film can't compensate for lousy glass. Compound that with tiny (comparatively speaking) imagers and the head starts aching again!

Howdy everyone!

It's now been over a week since I asked about any other image data on this test. First off as you can see above, John didn't say there wasn't any, but instead just asked me for exactly what I was lookin for. I obliged him generally, and then a little later I screen printed exactly what I seen in the search results to make me curious. By the next mornin the search no longer returned that result. Gone just like that, without a word to Adam. I still have my screen prints though, and this here is what I can reconstruct of what looks to be a different version of this here 'Major Flaw' report, (but this one talks about an extra fuji lens, to prove where the fault lie):

Long Focal Length PPF Test

We tested two megapixel rated lenses from Fujifilm [[part numbers]] As well as two HD PTZ cameras to see how image quality holds up under these long focal lengths. 

Using the 8-80mm at its longest focal length, visible quality was equivalent to images of 50% or lower PPF. [[100' 190 vs 80, 94 vs 45 etc. Additionally depth of field was limited. Focused on our subject at ~500, images were blurry around 250-300'. [[FOV example]]

To see if this was a function of long focal length or the lens itself we tested another lens, a Fujinon ___ 4-12mm megapixel rated lens, set to ~8mm, the same field of view as its 8-80mm counterpart. At this focal length, the 4-12mm lens is demonstrably better, providing approximately the PPF levels it should (X at Y distance)

So was this written before the test or after?

If after, where are those 'demonstrably better images' which prove the lens is at fault? I'm having a hard time thinking of any answers that don't involve either:

Writing the report before even doing the test and / or

Ignoring important but not helpful results to reach a foregone conclusion

Though the reason I can't think of an explanation might just be my own lack of imagination, so make-up your own mind! But based on the reception given to my earlier question and the removal of the search data, I'm not expecting an answer. 

Now that I've done said my peace, I will saddle-up and get out of y'alls hair.

The poor MTF at longer lens lengths is most likely source of the image quality issues.

Yes, it may very well be.

The 3MP fuji lens is listed at f/1.4 at 8mm, and although I can't find a published spec for it at 80mm, a conservative guess puts it at around at least f/3, possibly a good deal more.

Where the snb-5004's 1/3" image sensor looks to have a pixel width of ~3.5 microns

• A lens at f/2.8 corresponds to an airy disk of ~3.7 microns.
• A lens at f/4.0 corresponds to an airy disk of ~5.3 microns.
• A lens at f/5.6 corresponds to an airy disk of ~7.5 microns.
• A lens at f/8.0 corresponds to an airy disk of ~10.7 microns.

Note that severe diffractive effects aren't seen until typically the airy disk width is 2x the pixel width, although some distortion is noticeable at greater than 1x. So depending on what the effective f-number of the lens actually is, the sensor/lens combination may be indeed diffraction limited.

On the other hand it's hard to be sure because, at lower f-numbers the difference is small. One idea would be to retest the lens with a sensor with a higher resolution and smaller pixel width. Maybe try the SNB-6004 or even the 3 MegaByteMegaPixel 7004, as they may be easier set similarly, being in the same Wisenet III family.

If the image is merely resolution-limited then going to the higher resolution sensor should yield a substantial improvement. If the image is severely diffraction limited though the improvement should be minimal.

Thoughts/corrections?