One for camera buffs

Recently bought a Coolpix P900, love it.
We also have a DSLR. Looking at getting something with similar 'zoom' i've found myself a bit confused.
The P900 is a 24-2000mm equivalent (I haven't got my head around that yet) but it seems the the lens is 4.3-357mm. If I was to buy a lens for the DSLR would I be looking for 2000mm or (circa) 357mm?
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On 14/04/2017 19:09, R D S wrote:

Depends on the size of the image sensor in the DSLR. If its a true 35mm sensor, then you would need a 2000mm lens. If its the more common APS sized sensor then you get a magnification factor because the sensor crops the edges of the frame. The factor is typically about 1.4 to 1.6x, so you would need a lens in the 1200 - 1400mm range to get the same effect.
However for lenses that long, be prepared to pay an eye watering amount if you want anything of decent quality and also adequate aperture to actually let any light into it!
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On 4/14/2017 7:32 PM, John Rumm wrote:

+1, and forget about hand-holding it, you will need a substantial tripod unless you are resting it on a solid object using a bean-bag.
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We should drop this "35mm equivilant". Many digital cameras users have never used a 35mm camera. We should use "Angle of view" as a format independant reference.
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Quite. And I doubt the movie film 35mm target size has any real relevance to digital cameras.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

You'd need to standardise on which dimension you were referring to: horizontal, vertical or diagonal. Probably best to use diagonal then a) you are using the same convention as when specifying screen sizes for TVs and laptops, b) you don't have the added confusion that the long axis is vertical in a portrait picture and horizontal in a landscape picture.
I suppose you've got the added problem that the numbers would probably involve fractions of a degree so these may need to be marked on the lens barrel - unless you round to the nearest degree.
Was it only for TV work that lenses quoted in angles were used? In 16mm and 35mm movie and 35mm still, lenses are usually referred to as actual focal length. (NB: 35 mm movie and 35 mm still are different size frames: 18x24 for movie and 24x36 for still, because the film runs vertically in movie and horizontally in still, so the distance between perforations is the long axis in one and the short axis in the other)
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The reason angle of view was used in TV in the early days was there were different types of electronic camera in use. And someone planning say a drama wouldn't always know which studio he's get and therefore which type of camera. So he could work out is shots on paper using angle, and leave it to others to make sure the correct lenses were fitted to the appropriate camera - long before the days of zoom lenses being the norm.
IIRC, the standard lenses on a studio TV camera turret in those days were a 35, 24, 16 and 8 degree.
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On 15/04/17 14:07, DerbyBorn wrote:

The trouble is, it isn't format independent, is it?
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The user would know if the lens that matched his camera / sensor has a particular view angle and from that be able to imagine the field of view that would be achieved.
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Does anyone know or care what focal lenght lens is fitted to their phone? But they will be more aware of its angle of view, through using it. Same as with any camera. Which is why, to me, it is the more important thing to quote.
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On 15/04/2017 16:05, DerbyBorn wrote:

With DSLRs it still would not help since you will still get different results on a full frame model than you will with an APS one.
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On 14/04/2017 19:09, R D S wrote:

The difference is because the target size is different. Measure the view angle you get with the P900 and then choose a lens designed for the DSLR with the same view angle. If the vendors of the lenses don't quote it google lens conversion table or something.
Bill
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On 4/14/2017 8:39 PM, Bill Wright wrote:

P900 sensor is (only) 6.2 x 4.6 mm compared to 22.2 x 14.8 for Canon APS-C.
So the factor is about 3.5 and you will need a 1200 mm lens for a Canon APS-C DSLR for the same telephoto view.
You won't of course get an 83:1 zoom ratio on a DSLR. The convenience of such a thing as found on a superzoom compact (or camcorder) comes at the price of quality.
Check out professional sports photographers and you will see that they carry several cameras with different lenses (often zoom, but the zoom ratio is seldom more than about 4:1).
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From the early days of TV, lenses were always quoted as viewing angle - as different types of cameras had different target sizes. Never did understand why this wasn't done with photo lenses too. Even on the rare occasion where a lens will fit more than one type of camera.
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On 15/04/2017 00:25, Dave Plowman (News) wrote:

But the quoted viewing angle would only apply to one target size...
Bill
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On 15/04/17 02:17, Bill Wright wrote:

Sssh. It's our dave. Socialism has entirely rotted his brain.
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But how many lenses can be fitted to cameras with different target sizes?
Not saying you wouldn't give the actual focal lenght too - but stating the angle of view for each target size camera the lens would fit to wouldn't be difficult?
In other words, if the norm was to state the angle of view, you'd know what to expect with that in use. Across all platforms. Those who wanted to know the actual focal lenght could look it up.
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On 15/04/2017 11:43, Dave Plowman (News) wrote:

Most of them...
If you buy into one lens system (say canon, or nikon etc) they both have models of camera with a number of different sensor sizes - and they will all take the same lenses (mostly).

The angle of view will change with the sensor size in the same way the effective focal length will.
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"John Rumm" wrote in message wrote:

Found this page with a variety of interesting calculators: http://www.tawbaware.com/maxlyons/calc.htm
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With the same focal length lens, yes. The whole idea of stating angle of view for the combination.
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