ZOOM Magnification

jackdaw

Hi
what is roughly the magnification on 50mm ? 100mm ? 300mm?

if you are using a Canon 400D ?

mathias

Im not quite sure what your asking here , so I'll take a guess that you are looking for figures to compare with a compact and the way they are described , for example 3 X or 6 x or whatever.

On any zoom lens , the factor is the high (zoom or telephoto end) devided by the low ( wide) and this goes for lenses too , so for instance if you have a 10 - 200 mm lens then the zoom factor is 20 x , on a 70-300mm the factor would be 4.3 and so on.

If on the other hand you are talkin about how close it brings your subject when using a prime then thats another story.

On a 35 mm camera or a full frame camera , one that has a 35 mm sensor , a 50mm lens is generally considered to be closest to what the human eye sees.

So if you take that figure and divide your lens focal length by it then you have a rough magnification factor for 35mm

On a 400D , which has a smaller sensor , you would use 30 as a 30mm lens would give you the same as a 50mm on a full frame camera.

Is any of the above what you meant ?

Hugh_C

jackdaw wrote: »

Hi
what is roughly the magnification on 50mm ? 100mm ? 300mm?

if you are using a Canon 400D ?

If you're talking about crop factor I think it's 1.6

jackdaw

so at 300mm , is the magnification approx 300/35 ?
8.5X ?

mathias

From a human eye view to 300m , yes , approx X 8.5 , although I would have used 30 because on a 400D a 30mm lens would be equivalent to a 50mm on a full frame.

30 x 1.6 = 48mm ( close enough ). and that would give you a " zoom" factor of 10 or so.

Thirdfox

Well don't human eyes have a focal length of around 45/50mm (in 35mm terms)? Hence the most common primes being 50 for photojournalistic purposes?

mathias

Yup , as posted above , but you have to take into account the crop factor on the 400D so were using 30mm

PopeBuckfastXVI

I was looking at my mates bridge before, which had a "10x" zoom at the high end, I put it up to 10x and put my lens out to 200mm on a Nikon d80 (dx sized sensor) and the crop was the same.

I'm not sure where the 3x zoom etc. you see on compact and bridge cameras comes from, I think it's just a gimmick to be honest.

mathias

I'm not sure where the 3x zoom etc. you see on compact and bridge cameras comes from

Its a simple enough calculation , if you look at the specs for any compact and look at its actual focal length range and focal length range in 35mm equivalents ,

take the high number , devide by the low number , and thats your zoom.

www.dpreview.com lists specs for all compacts etc. Check and see !

For example here is the lens specs for a Canon powershot A720 IS

• 5.8-34.8mm (35-210mm equiv)
• F2.8-4.8
• 6x optical zoom

So , 34.8 / 5.8 = 6 and 210 /35 also = 6 hence the 6 X zoom

If the view from your mates camera was the same as your 200mm , then that must have been his maximum focal length and it must have started at 20 or so to get 10x zoom . ( although to be honest the lowest Ive seen on a compact was about 24 ).

Edit , forgot about the crop factor on Nikon , silly me , so your 200 would be equal to 300 and his must have had a range of around 30 to 300! That would have been more like it.