Theoretically, long lenses should let you capture faces and license plates very far away.
For example, over 900 feet away from a 1080p camera one should get over 40ppf from a 100mm lens.
But how well does this work in practice?
In this test, we took 3 long lens cameras, including:
We ran tests from 100 to 500 feet away from the cameras, comparing the theoretical PPF to the actual achieved.
Can one really deliver such distances or are there quality issues for long lenses?
IPVMU Certified | 08/27/14 04:53am
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.
"For the stadium, we used a 5-megapixel camera at 75-feet wide and 34 pixels per foot (ppf). Then we opened up to a higher resolution: 10-megapixels at 110-feet wide at 33ppf. We tried a 25-135mm lens that performed great with the camera and became one of the lenses they ultimately used in the installation. After seeing several different...
Isn't some of the quality degradation explained by motion blur, which is intensified as you zoom? Could be due to unseen vibrations, e.g. due to nearby machinery/natural harmonics of the pole, etc. I would try putting your finger on the camera enclosure and check if it has any impact on the directionality or intensity of the blur.
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....
Does the test hold true for PTZ at standard definition at these high focal lengths? I recall reading several years ago that the glass in the lens of most high pixel cameras don't support anywhere near the pixel densities of these compact cameras. There has to be good reason a digital SLR camera has a lens that is 10x the length and width of a lens used in a typical HD security camera.
The important point is not the size of the sensor and the focal length of the lens, you have to think about the angular size of the pixel as it maps onto your targets. So it's the ratio of these two quantities that is important. Lenses are all about bending light and angles. The lense has no idea what sort of sensor you're going to put behind it. But really, I think the problem here is not...
IPVMU Certified | 09/04/14 01:39pm
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...
Howdy Ethan! Do y'all have a link for any additional images/detail that go with this test?
Maybe I jumped the gun there, I thought this search result was referring to the same test as in the Flaw Found one? Maybe supplemental info? Or an outline? But it says 'try back later once its posted', so I reckon I'm wondering when that will be...
(In case my...
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...
IPVMU Certified | 06/07/15 03:46am
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...