Magnification on lens

phinix

phinix

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To clarify - if lens has 0.25 max magnification, what does it mean?
My kit lens Sony 18-70 has 0.25 max mag and for example Tamron 17-50 has 1:4.5. Which one gives better macros then?
Please explain:)
 
The max magnification of a lens defines the size of the object projected onto the film or sensor.

A magnification of 0.25x means that your kit lens will project an image 1/4 life size when the lens is focussed as close as possible. Assuming you haven't quoted the aperture for the Tamron lens then 1/4.5 = 0.22x...ie, a little less than the kit lens.

HTH

Bob
 
1:4.5 means that the maximum magnification ration is 1/4.5, which calculates to 0.222. So your kit lens has a slightly greater maximum magnification, but there's very little in it.

Right - now what do the numbers mean? Basically, it's how big the image of a given object is on the sensor, when the lens is at maximum zoom and minimum focus distance. Under these conditions, an object that is 1 cm across in real life will be 0.25 cm or 0.22 cm across on the sensor. Now, the sensor on your Sony A300 measures 23.6 x 15.8 mm. So at 0.25x you can fill the frame with an object which is 94 x 63 mm, and at 0.222x you can fill the frame with an object which measures 106mm x 71 mm.
 
I think you can't explain it any better than that - really thank you guys! Now I got it!:)
..and really need that Sigma 50mm 1:1 macro... ;)
 
Last question - about extension tubes - if it says its 25mm, what does it mean? what will that add to max mag. from lens?
 
The amount of increase in magnification depends on the focal length of the lens. You'll get more increase per mm of extension as the focal length shortens....ie, the wide ends of your zooms will benefit more than the long end.

Bob
 
phinix said:
I think you can't explain it any better than that - really thank you guys! Now I got it!:)
..and really need that Sigma 50mm 1:1 macro... ;)
Click to expand...

We've the Sigma 50mm Macro lens and it's a cracker - occasionally it would be nice to have the 100mm or larger so you can be further away from the object - will make no difference to your shot / magnifcation etc just you can be further away from the object , but for me, it's not often a problem and wasn't worth the additional money :thumbs:
 
This is how it looks if you take a picture of a tape measure - this was a nikon D300 so its a 1.5x crop sensor


1 - 1:1 often called true macro or life size

1-1.jpg


2 - 1:2 or Half life size ie you can see twice as much of the tape measure.


1-2.jpg
 
Thank you all for explaining it to me.
 
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