At 1:1 a bee that is 2.0 cm long in life will 2.0 cm long on 36x24 and 2.0 cm long on 6x6 and still 2.0 cm long on 4x5. 1:1 means exactly the same thing on all formats.
Dave Hartman
Point missed, but I think I am at fault for my prior wording.
1) I realize it's not the bee that changes, my point was it's
the framing.
2) I also wasn't speaking of 6x6 or 4x5 ... no one uses these for bee or macro photography.
I understand that 1:1 magnification = 1:1 magnification; that's a tautology.
So, yes, the reproduction ratio remains the same.
The point that is continuously being missed is 1:1 on a 36mm sensor might be too small ... and on another sensor it might be too large.
I can see how I worded it wrong previously, so let me re-phrase:
Let's say I am trying frame a 16mm subject with a 2:1 lens.
At its closest distance, a 2:1 lens reproduces 18mm of subject across a 36mm sensor, doubling the reproduction ratio.
So a 2:1 lens would be perfect for trying to capture a tight shot of 16mm subject (
if I shoot FF).
The 16mm subject has its reproduction ratio doubled, to 32mm, which fits nicely on my 36mm FF sensor.
However, if I tried to use that same 2:1 lens on a crop 1.5x DX sensor, this means I will be trying to place 32mm of augmented subject on my 24mm sensor ... so some part of the subject will be clipped off.
When shooting macro, I can't just think 1:1 or 2:1 magnification; I have to think of 1) the size of my subject, 2) the magnification, and 3) the size of my sensor.
Saying 1:1 (by itself) is meaningless for macro composition.
These 3 questions have to be asked:
- What size subject is being considered for the macro shot? (4mm? 12mm? 30mm?)
- What is the reproduction ratio of the lens?
- What size sensor am I using?
If I know a 20mm AI-S lens offers 3.4x magnification, reversed, this means a 10 mm subject will be magnified to 34mm, which will fit on a 36mm FX sensor.
That same 10mm subject will magnify to the same 34mm using the 20mm AI-S
on a DX ... but
34mm won't fit on a 24mm DX sensor.
If I know the 20mm AI-S offers 3.4x magnification, reversed, this means (if I am shooting a DX) that sensor can only handle ~7mm (with that 3.4x multiplier) before the reproduction ratio exceeds a 24mm sensor.