Have always been confused about this....
1. What exactly does true macro photography with 1:1 magnification means? Am i right to say that....
It means with for example that a 90mm 1:1 lens and a 36mm wide sensor, should show an insect that measures 36mm from head to tail (left to right) at a distance of 90mm from the insect to the optic centre, covering the entire width of the resultant image?
... which means that if the insect is 180mm from the optic centre, the frame will cover 72mm width, and the 36mm long insect will cover half the width of the frame?
... and if the minimum focusing distance is 270mm, the frame will cover 108mm width, and the 36mm long insect will cover a third of the width of the frame?
and if my sensor width is 18mm with a conversion factor of 2, at 1:1 magnification factor of the 90mm lens,
if the insect is 90mm away from the optic centre, the resultant image only capture 18mm centre portion of the 36mm long insect
if the insect is 180mm away, then only will a life-size 36mm long insect fills up the width of the image on the 18mm sensor.
if the insect is 270mm (3x90) away, the frame will cover 54mm (3x18) with the 36mm long insect covers 2/3 of the picture instead of 1/3 of the picture.
essentially the change of sensor size with a conversion factor of 2, doubles the apparent magnification by 2 (subject fills up half the frame at 180mm distance at 36mm sensor size but fills up the whole frame at 180mm same distance with a 18mm sensor size), even though the actual magnification of the sensor size v.s the subject size is still 1:1.
And with a reduction of sensor size by half, it will have a reduced angle of view and field of view, with a change of perspective from what a 36mm wide sensor will see at 90mm focal length, but this 18mm wide sensor using a 90mm lens instead will have the same perspective of what a 36mm wide sensor will see at 180mm focal length, with the same angle of view, requiring the same 36mm long subject to be at 180mm away instead of 90mm away to fill up the width of the image.
If the angle of view is changed by the reduction of sensor size, the perspective of near and far objects also changes, so is it true that people say a 90mm focal length lens will retain the perspective relationship of a 90mm focal length even with a change of sensor size?
2. does magnification factor always change with a zoom range macro lens? is it true that as long as a macro lens is zoom and not prime, it can't possibly have a constant magnification factor of 1:1. and hence true constant 1:1 magnification factor can only be achieved by a prime lens?
3. how exactly does the framing differs between a 90mm normal lens and a 90mm macro 1:1 lens?
if arbitrarily a 90mm macro 1:1 lens appears to cover the width of the same subject as a 90-270mm lens will do at 270mm focal length, would the perspective, angle of view and field of view be that of a 90mm or 270mm?
1. What exactly does true macro photography with 1:1 magnification means? Am i right to say that....
It means with for example that a 90mm 1:1 lens and a 36mm wide sensor, should show an insect that measures 36mm from head to tail (left to right) at a distance of 90mm from the insect to the optic centre, covering the entire width of the resultant image?
... which means that if the insect is 180mm from the optic centre, the frame will cover 72mm width, and the 36mm long insect will cover half the width of the frame?
... and if the minimum focusing distance is 270mm, the frame will cover 108mm width, and the 36mm long insect will cover a third of the width of the frame?
and if my sensor width is 18mm with a conversion factor of 2, at 1:1 magnification factor of the 90mm lens,
if the insect is 90mm away from the optic centre, the resultant image only capture 18mm centre portion of the 36mm long insect
if the insect is 180mm away, then only will a life-size 36mm long insect fills up the width of the image on the 18mm sensor.
if the insect is 270mm (3x90) away, the frame will cover 54mm (3x18) with the 36mm long insect covers 2/3 of the picture instead of 1/3 of the picture.
essentially the change of sensor size with a conversion factor of 2, doubles the apparent magnification by 2 (subject fills up half the frame at 180mm distance at 36mm sensor size but fills up the whole frame at 180mm same distance with a 18mm sensor size), even though the actual magnification of the sensor size v.s the subject size is still 1:1.
And with a reduction of sensor size by half, it will have a reduced angle of view and field of view, with a change of perspective from what a 36mm wide sensor will see at 90mm focal length, but this 18mm wide sensor using a 90mm lens instead will have the same perspective of what a 36mm wide sensor will see at 180mm focal length, with the same angle of view, requiring the same 36mm long subject to be at 180mm away instead of 90mm away to fill up the width of the image.
If the angle of view is changed by the reduction of sensor size, the perspective of near and far objects also changes, so is it true that people say a 90mm focal length lens will retain the perspective relationship of a 90mm focal length even with a change of sensor size?
2. does magnification factor always change with a zoom range macro lens? is it true that as long as a macro lens is zoom and not prime, it can't possibly have a constant magnification factor of 1:1. and hence true constant 1:1 magnification factor can only be achieved by a prime lens?
3. how exactly does the framing differs between a 90mm normal lens and a 90mm macro 1:1 lens?
if arbitrarily a 90mm macro 1:1 lens appears to cover the width of the same subject as a 90-270mm lens will do at 270mm focal length, would the perspective, angle of view and field of view be that of a 90mm or 270mm?