vinod joshi
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How to calculate optical zoom in nikon 300mm telephoto lense in terms of 5x,10x... Etc?
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Nikon 300mm tele lens
- Thread starter vinod joshi
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Labe
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It's a 1* . It is a prime lens , not a zoom. It is 300mm
marketing uses this 10times, 83times etc to draw you in to their products but it doesn't actually tell you how much magnification/focal length you actually have . So if you are now using an inter changeable lens camera instead of a super zoom you need to look at the actual focal length figure. The larger that number the greater the reach .
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marketing uses this 10times, 83times etc to draw you in to their products but it doesn't actually tell you how much magnification/focal length you actually have . So if you are now using an inter changeable lens camera instead of a super zoom you need to look at the actual focal length figure. The larger that number the greater the reach .
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If you mean the magnification factor, then for a full-frame camera it's x6 (i.e. 300mm/50mm) and for a DX camera it's x9 (i.e. effective 450mm/50mm).
mdmarqphoto
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Not true. There is no "zoom" in a prime lens, and you don't compare a lens to a 50mm lens. On a superzoom/bridge camera, the multiplier refers to how much greater the long end of the zoom lens is to the short end. On ILC cameras this multiplier isn't used, but you can figure it out. But again, the OP asked about a specific focal length lens, not a zoom.
Astrotripper
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You take focal length at the long end and divide by the focal length at the short end.
Since it's a prime lens, that makes the equation look like that: 300 / 300 = 1. Which means zoom factor of x1, which is no zoom at all, which makes sense since it's not a zoom lens.
For example, popular telephoto zooms like 100-400mm would be x4, so are the 150-600mm zooms (600 / 150 = 4).
I'm not talking about a zoom, I'm talking about a prime lens. I'm also not talking about bridge cameras, which are irrelevant to the discussion.
When working out magnification factors, you relate it to a 'standard' lens, which for FF is 50mm. Lenses on DX cameras have a 1.5x uplift, to match the cropped sensor.
Quite... It's a meaningless question in that context - so, what question is the OP actually asking?
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Astrotripper
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Who knows. Maybe he will come back and clarify. Or maybe now, knowing the above equation, he will be able to calculate the thing he wants to calculate.
john isaacs
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That is not how image magnification is computed. It is a measure of how large the projected image is (on the sensor) with the actual size of the image. It is a function of focal length, close focusing distance, and sensor size. It is not simply a ratio of focal length. Macro lenses, for example, typically have an image magnification of at least 0.5 (1:2 ratio) or at least 0.1 (1:1 ratio).
The Nikon 300mm f/4 lens has image magnification of 0.24 (and close focus distance of 1.4m. Which makes it pretty handy for shooting close-ups.
I strongly doubt that this is what the OP was talking about, though... Their post said " in terms of 5x,10x", so I doubt that the answer that they were after is 0.24...
If they return, we may find out what they actually meant.
john isaacs
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The obvious answer is 1x, since the lens is not a zoom. I wonder if that is the answer they were looking for.
There are two questions/answers that make a bit of sense to me.
A first question could be "what is the zoom magnification that gives, at the long end, the same reach as a 300mm prime? ". It doesn't make the most sense but I can understand where the question comes from. The answer of course is that it depends on which focal length the zoom starts out with at the wide end.
A second question I've seen is something like "if I wanted to see the same scene visually, e.g. with binoculars, what magnification would they need to be to match a 300mm lens?". Here again the answer is 'it depends' but in first approximation it's the lens focal length divided by the diagonal size of the sensor it is used on. In the case off a FF camera 300 mm / 43 mm = 7x.
vinod joshi
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Thanks a lot
mdmarqphoto
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You didn't mention zoom, but he OP did, and a prime 300mm telephoto lens has no "zoom". The numbers the OP mentions (5x, 10x) sound more like how lenses on non-ILC's are described. You seem to be talking about "crop factor", which might be the right subject, but still, you don't use a 50mm (or "standard") lens to compare crop factors. You compare the amount of the image circle hitting the sensor by the same focal length lens.
Agreed.... Albeit Nikon have always promoted/used 50mm as a 'standard' lens on 35mm.
john isaacs
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Not always. The 55mm was "standard" until they designed the 50mm.
OK - change the 'always' to 'since January 1962', then...
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