Hi All,
My lens has a magnification of 0.24x at maximum zoom (200mm). I added in a +2 close up filter. What is my magnification now?
Sorry if it sounded noob. I am really new to this end of the photography. Many thanks in advance.
I have done the measurement and calculation last night.
I am using a 200 mm lens on a Canon APS-C size sensor. The crop factor is 1.6, so this is equivalent to a 320 mm lens on a 35 mm film size.
APS-C sensor size = 14.9 x 22.3 mm
No close-up filter = 49 x 74 mm to fill up the image at min focusing distance
With +2 close-up filter = 38 x 58 mm to fill up the image at min focusing distance
Dividing the sensor size by the captured image:
Max magnification with no close-up filter = 0.31x (same as what is measured by dpreview)
Max magnification with +2 close-up filter = 0.38x
Dividing the image (with +2 filter) by the image (no close-up filter) = 1.3x
The common formula to measure magnification:
For a +2 close-up filter on the 320 mm lens = 320/(1000/2) = 0.64x
For a +2 close-up filter on the 200 mm lens (ignoring in the 1.6 crop factor)
= 200/(1000/2) = 0.4x (similar to what I measured at 0.38x)
So, my questions are:
1. Why is the magnification given by the formula (0.64x) different from what I measured (0.38x)?
2. Should I ignore the 1.6 crop factor when applying the formula (0.4x is close to what I measured)? Dont think I should ignore the crop factor because the final effect on the sensor is equivalent to the 35 mm size.
3. Maybe my +2 close-up filter is not really +2, but only +1.25?
does it matter?
to me only the resulting image matters
nice or not nice
so what if i have a 5:1 micro lens if i cannot take nice pictures with it
I agree that it does not matter what the magnification is. However, I do not want to be short changed as well. I just want to make sure I have a +2 and not something less.
The common formula to measure magnification:
For a +2 close-up filter on the 320 mm lens = 320/(1000/2) = 0.64x
For a +2 close-up filter on the 200 mm lens (ignoring in the 1.6 crop factor)
= 200/(1000/2) = 0.4x (similar to what I measured at 0.38x)
The article by megaweb in is link give you abroad idea of macro and close-up photography. And also about magnification in relation to lens focal length and minimal focal distance.
http://www.clubsnap.com/forums/showthread.php?t=261356
yes, I applied the 1.6x crop factor in the calculation for the close-up filter. Just that in this case, the calculated results is closer to the real measurement if I don't include the 1.6 crop factor. Which I doubt is correct.
Aiyo~ kid nows a day ah..
Just put on and shoot la. :sweat:
Y so many calculation. Theory is nice but practical is much useful in real life.