Per this story apparently Trump is not very careful with where he chooses to discuss military and and national security issues. Hypothetically if some top secret papers were on the table with standard 10 or 12 point fonts on an 8" x 11" page what is the maximum distance from the table a high quality professional news camera and lens setup could take a pic and be able to clearly read the page information?
I can’t give you a precise answer, but conciser that you can do this with a cheap consumer-grade camera using cheap consumer-grade lenses and a tiny (and therefore noisy) cheap consumer sensor. Put expensive professional glass in front of a large CCD, and I wouldn’t be surprised by a figure in the “miles” range.
Really, it’s going to depend on where you draw the line between “telephoto lens” and “telescope with camera mount”.
Eventually you will run into atmospheric distortion. Even that can be mitigated, with some success. Otherwise one would simply be talking the usual resolution limits on the optics involved.
What might be the range of said limits for optics of the type postulated in the OP?
You can read a car’s license plate from orbit. And that was just the abilities they were willing to go public about in 2014, so who knows how much it’s improved, or what they aren’t telling us.
For the OP’s actual scenario - which is basically a pro news photographer with top end gear (something of a dying breed now) the limits will really be from the sensor. If you assume that the reporter has come to cover a press conference or other media event they will have a passably long focal length lens - whereby they can get full frame head and shoulder shots from the opposite end of the room (where they are often restricted to be located - giving the reporters the closer in positions.) So they will have some reasonably serious glass. Not quite sports photographer, but probably of the order of 3-500mm equivalent. Someone with a full frame SLR (Canon D1X say) is going to have little trouble from the end of a large room. Of course the OP doesn’t take into account that the documents will probably be laid flat, making them impossible to view. If we want to read them at a very shallow angle it is going to be a lot harder. The needed resolution is vastly higher. Depth of field will be difficult to manage as well.
I was really alluding to the fundamental limits on optical resolution - the Rayliegh criterion or Abbe Limit. For the OP, with a conventional camera, you will hit the resolution limits of the sensor before the lens. So it is likely just just determined by spatial resolution of the sensor (which is related to, but not just about how many pixels it has.)
Not really. The article says:
The smallest thing it can resolve is something 31cm across. So it can see if a car has a licence plate or not. A fuzzy white blob. To actually read the plate you would need resolution a good 30 times better. This is heroic technology. From 300 miles up, through the atmosphere. There is little to no chance they can read number plates.
Zoom and enhance!
I’ve never been a photographer, but I found your links so amazing I want to ask for a Nikon P900 for my birthday! What’s the catch? (I assume those shots needed a tripod!)
The P900 has built-in “VR” (Vibration Reduction), which helps stabilize the image, but a tripod always helps. Lots of light helps, too. You are not going to be able to take sharp super-zoom photos indoors, in most cases, unless you crank the ISO up.
The problem is balancing telephoto ability with portability.
This picture was taken from 1/2 mile away using a Canon 1200mm EF lens but it is barely man-portable and you absolutely need a tripod.
You can see in that picture “1875” on the bridge. I am guessing those numbers are about 8" tall.
The more you zoom in the more fuzzy the picture will get without stabilization.
This lens, the [Leica APO-Telyt-R 1:5.6/1600mm](Leica APO-Telyt-R 1:5.6/1600mm), is a one off and cost $2 million. For stabilization the sheikh who bought it supposedly had a custom Mercedes built to act as a mount. No photos of what this can do have been released.
Here’s a comparison I made a few years ago.
50mm focal length.
1200mm focal length.
There is some image blur due to windy conditions and a not-heavy-enough tripod, but you get the idea. The houses in the photo are around 8 miles away.
The “56th Street” sign is just over 1/4 mile away.
Back in the mid-70’s, Popular Photography(? I think) had an article by some guy who covered a summit in Helsinki. For fun, he took a big zoom into the press gallery. He says it did not seem to occur to security what the implications were. He took some photos over Kissinger’s shoulder of classified documents which the magazine published, including the “TOP SECRET” stamp - they were basically a reprint of newswire stories (he obviously declined to print anything more secret, assuming he saw anything).
About 20 or 25 years ago, the finance minister in Canada was doing a photo op of the next day’s budget, wearing the traditional “new shoes”. He riffled through a copy of the budget from about thirty feet away. The TV news people realized that freeze frame allowed them to read portions of the budget, which were supposed to be top secret in parliamentary venues, since it affects markets. The finance department was up all night re-working the budget to change the leaked details.
When I’m on vacation, I also include in holiday photos pictures of those big, boring signs with detailed explanations of what I’m looking at. Even 15 years ago with a 2.4Mp camera, these signs were very easy to read.
The other important issue is lighting. Low light and big zoom don’t always mix. The total amount of light the lens gathers is determined by the diameter of the lens. The relative amount is f-stop, diameter divided by focal length. Good photos usually are around f2 to f22. Above f22 or so you get into diffraction issues IIRC. Plus, to get enough light you would need long exposure, meaning the target has to stay still for a while - not something you can count on when sheets of paper are being shuffled and waved about in low light. With insufficient light you might get something recognizable but too grainy to be readable.
I was intrigued, so I did some math. Thisshows pictures of Desert View Watchtower taken from Lipan Point, distance of about 2700 meters.
At maximum magnification, the resolution is about 2 dpi. After some trials exporting jpgs from pdfs, 50 dpi seems to be the bare minimum for reading 11 point Times New Roman.
So provided somebody was holding a nice printout in bright light, the above mentioned camera could read it from up to 100 meters.
There is math that can solve this. Math that is at the limits of my math abilities so I will leave it to some other mathematically inclined Doper to figure it out.
So, I guess you have to work backwards determining the size of a standard font on the page and then graphing a slope that tracks distance vs lens size (or focal length?).
It’s beyond my abilities but seems it could be figured out on paper.
Yep.
I think that, in the realms of the realistic, a pretty solid combination would be something like the latest Nikon 500/f4E FL lens, mated with a 1.4x teleconverter, and mounted on a good-quality APS-C sensor DSLR like the D7200 or D500. The smaller sensor gives the lens a focal length equivalent of 750mm, and adding the teleconverter would leave you with an effective 1050mm/f5.6.
Reviews suggest that the 500/f4E FL lens, which, at 6.8lbs, is almost two pounds lighter than its 500/f4G predecessor, can produce very good shots handheld, and outstanding shots on a monopod. The vibration reduction helps.
If you wanted similar reach with in a more discrete and portable package, you could try Nikon’s 200-500/f5.6E which, with a 1.4x TC at the long end of the zoom, would give you the same 1050mm reach, but with a maximum aperture of f8, which is about the limit that the autofocus system can deal with. This lens is only 4.6lbs, so much easier to carry and shoot handheld.
You’d probably have to crank up the ISO quite a bit, but the new D500 has incredibly good high-ISO performance, and if all you’re after is readability rather than fine image quality, it would probably work pretty damnwell.
I’ll see your 1600/f5.6 and raise you a 1700/f4 !!! Lord knows what that cost, but considering it was apparently produced for some guy in Qatar, i’m betting money wasn’t really an obstacle.
Interesting that these mega-lenses are described as meant for wildlife photography.
Is there something we have been missing with more normal telephoto lenses that such monsters are needed? What wildlife shots have been missed?
I mean, the technology and lenses are cool and all but c’mon.
I suspect these lenses have other uses than taking pictures of lions.
Spelling mistake. It’s for taking pictures of loins.