Red and Blue

by Gordon

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When you took the photo with a 300mm length, it got cropped on a crop sensor. You didn't actually get a 450mm photo, but still a 300mm cropped photo. With full frame, it will still take the same photo but without any cropping. If you crop it in photoshop then you will get the exact same photo as your crop camera... you are basically not missing out on any ...


To get the same reach as the long end of your 70-300mm lens on an APS-C body, you need a lens with a focal length of 450mm on the D750. To get any Nikon lens with that kind of focal length at f/5.6 or wider requires a substantial expenditure compared to what you paid for the 70-300. The Nikon 500mm f/4 sells for about $7,900 new. The 400mm f/2.8 runs a ...


To get the equivalent FoV ("reach") on full frame that a 70-300 has on 1.5 crop would require a (70-300)*1.5 = 105-450mm lens. This will probably be at least twice as expensive as a 70-300, and will definitely be larger and more difficult to handle. Make sure you're ok with the possibility of relearning technique or adding stabilization--and possibly ...


The driven part of the AF coupling in the lens should be easy to turn for the entire travel. Most of the mechanical parts that make the AF happen are toward the front of the lens, so removing the lens mount and poking around isn't likely to net you anything. In your situation, I'd send it in if you can't get a refund. $200 for the lens plus $375 for Nikon ...


Are you sure you don't have the focus limiter switched on? It signals the lens that you want to focus either close, or at a distance, and prevents the lens from "hunting". If you turn off the focus limiter, the lens should focus from it's nearest point out to infinity. If you switch to manual focus, does it get sticky as you get to the 10m mark?


Part of the reason is doubtless that professional photographers earn more money than professional astronomers, and so can be milked a bit more for their cash. Score: +5 Funny


Astronomers use reflectors mostly but are indeed interested in accuracy. The lens in question is much faster than a telescope.


Michael Clark missed one important point in his otherwise correct answer: Physical vs. Optical length Think about what the 1200mm really mean. This is the focal length. This normally means that the distance from the center of the lenses to the place where the image forms is 1200mm. (Yes 1.2 meters!) On your telescope I guess that you pretty much see these ...


Different tools for different jobs. A telescope is for looking at objects with the naked eye, a camera lens is for recording high resolution images. It is acceptable for a telescope to have large distortions around the edges and nobody much cares about colour correctness. This makes it simple (cheap) to make the lenses which are good enough to do the job. ...


Rarity. There were only approximately 20 of these now out of production lenses ever made. When they were in production they sold for about $90,000 (US). Due to the time needed to grow the large fluorite crystal used in the 3rd element of the lens, once ordered they took about 18 months to produce. Autofocus Capability. These lenses include auto focus ...

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