I’m preparing to take a photo in May, using my ancient Criterion 4000 telescope. This is effectively a 1200 mm lens. Here are two photos taken from the same spot. This is using a 50mm (“normal”) lens:
I have outlined the area that the next photo encompasses.
Here is the 1200mm view:
The blurring is mostly due to vibration - it was windy, and my tripod isn’t sturdy enough. Even the slightest vibration caused the image to dance around. These sort of magnifications require very careful technique, which is why I’m practicing.
You have some nice clean cool air to work with there.
Find an old survey tripod, that is what I use to really hold steady in a breeze… Modify with a standard bolt, 1/4 in. I think on most camera bases. Check thread count.
BTW, I used Google Earth to determine that the houses are around 7.5 miles away.
a 50mm lens would be a standard lens so a 1200mm lens would be 24 times as powerful.
I think, given the OP’s focus on paparazzi-style pictures, that for practical purposes the lens we’re talking about here is probably a 600/4, or perhaps an 800/5.6. Nikon and Canon each do a 600/4 for upwards of $7,000, and Canon and Sigma do an 800/5.6 for about the same sort of money (prices taken from the B&H website, a very reputable dealer).
Now, with a 600/4, you can use a 2x teleconverter to get yourself a 1200/8 lens. Also, if you’re not using a full-frame digital SLR (like a Canon EOS1 DS MkIII or a Nikon D3), your effective focal length is even greater. Digital SLRs from Canon and Nikon with smaller sensors have a conversion factor of anywhere from 1.3 to 1.6, meaning that, with one of those cameras, your 600/4 lens could be a 780/4 through to a 960/4. And with the 2x teleconverter, you get anywhere from 1560/8 to 1920/8.
While f8 might seem like too small an aperture for useful pictures, especially with such a long lens and the need for decent shutter speeds (to avoid camera/lens shake), it’s also worth remembering that the latest generation of digital SLRs have pretty amazing low-light capabilities. The Nikon D3, for example, gives unbelievably good-quality images at ISO6400, and perfectly decent images (especially for paparazzi-style images) at 12800 and even 25600. Here’s a sample picture from a D3 at 6400.
So, let’s assume our budding paparazzo has a D3 (full-frame), and a D200 (1.5x lens factor). That means, with a 600/4 lens and a 2x teleconverter, he has the capability to shoot at 1200/8 (D3) and 1800/8 (D200). According to the table provided here, with a 1200mm lens on a full-frame SLR, we get a horizontal angle of 1.72[sup]o[/sup]. On the D200, this would reduce by one third, giving us a horizontal angle of about 1.15[sup]o[/sup].
Now, say we want to turn our camera sideways, so the horizontal axis is now vertical, and take a portrait-format picture of a person that fills 2/3 of the height of the frame. And say, for argument’s sake, that our subject is 6’ tall. That means we need the horizontal angle of the camera to cover a span of 9 feet. Now we can try to work out what sort of distance we need for 1.72[sup]o[/sup] and 1.15[sup]o[/sup] (respectively) to give 9’ of horizontal coverage.
According to the calculator on this page, a 1200mm lens on a full-frame SLR (lens factor 1) at a distance of 300 feet will give a horizontal field of view of 9 feet. And a 1200mm lens on a camera with a lens factor of 1.5 will give you 9’ of horizontal angle at a distance of 450 feet.
So, with a 600/4 lens and 2x converter on your full-frame SLR (the D3), you could stand 300 feet away from your 6-foot-tall subject, turn your camera on its side, and get a portrait-style picture in which the subject’s full length took up 2/3 of the image height. And with a 600/4 and 2x converter on your D200, you could get a similar shot from 450 feet away.
And with the resolution of these cameras, and the ability to blow up portions of the shot, you could get perfectly recognizable images from at least double those distances. With that lens on a D3, i think you could get a shot perfectly good enough for a website, and probably good enough for printing, from up to 1000 feet away. In fact, as some people in this thread have already suggested, the most important limitation on shots like this probably would not be the equipment, but rather the clarity of the atmosphere, because at those distances any haze, fog, or smog is going to have quite an impact on the quality of the shot.
Mhendo gives a good analysis, there.
Other comments: Forget about shooting from a boat with a big telephoto lens, the rocking motion would destroy the image. If you have a convenient cliff side you could theoretically go with the 1200 lenses, or…
The biggest readily available telescopes that are somewhat usable for terrestrial photography are the 200 series Meades with 16" apertures.
With the field tripod (shown) they run about $15,000, and weigh over 300 lbs. Meade lists the specs as 4064mm at f-10.
The new Olympus digital SLRs with the Four/Thirds sensors have a lens factor of 2 to 1. So, the telescope would function (I believe) as an 8000mm lens. But maybe not. I’m not experienced with using telescopes for photography.
An 8000 mm lens would make something 1600 ft away, seem about 10 feet away.
Like other catadioptric lenses you can’t control the aperture, and there wouldn’t be any autofocus.