Keep in mind though that 50mm macros of that era focused only to 1/2 lifesize without extension tubes. Additionally, the 50's varied in image quality, whereas the 90-105 macros were very consistent across the board and you'd be hard pressed to find an old macro lens in that focal range that wasn't exceptional. Additionally, the 90-105mm macros went all the way to lifesize magnification without extension tubes.
That's good to know. Always glad to be corrected and learn something when I am wrong.
But the OP and I myself are using 2X crop sensors. Wouldn't that compensate for the lesser magnification when 50mm macro's were used for film?
Yes and no. Lifesize is lifesize regardless of the sensor size. So, whereas lifesize in 35mm equivalent would mean taking a shot of a 36mm object, which would fill the frame, in 4/3, the magnification would be the same, but you would only see 18mm of the object. So, it seems as though you're getting a lot greater magnification because you're cropping, but all you're doing is cropping.
True.
If the pixels are smaller on the smaller sensor, you may be able to record finer details on the subject, at the same on-sensor magnification. (I say "may" because diffraction often limits the resolution of detail.)
I beleive it plays out like this:
Suppose I want to take a picure of a 36mm object. When I'm done I want the object to cover the entire image, and I shall display it at the full size of my computer screen.
With a 35mm Full Frame 16MP camera, I want a 1:1 magnification so the image covers the long edge of the sensor, 36mm with 4899 pixels. So, 4899/36 = 136 pixels per mm of the the object.
With an M43 16MP camera, I choose just under a 1/2x magnification (48%) so that the image covers the long edge of the sensor, 17.3mm with 4619 pixels. So 4619/36 = 128 pixels per mm of the object
Considering
only the number of pixels and object detail, the resolution of object detail is slightly less for M43 due to the aspect ratio. If the example had been for a smaller 16MP sensor with a 3:2 aspect ratio (as for APSC sensors), the number of pixels on the long edge would be the same, and resolution of object detail would be the same.
However dynamic range and noise are also affect detail resolution. These factors are dependent on sensor technology, selected ISO, and the crop factor of the sensor. Different conclusions can be shown depending on what factors you decide to hold constant.
Assume the same sensor technology, pixel count, object lighting, object distance and field of view. To hold the same field of view, the focal length must be in proportion to the crop factor.
If you hold the F stop of the lens constant,the shorter lens will have a smaller entrance pupil. Light collected is determined by the area of the entrance pupil. The smaller sensor will have less light (and less light per pixel) due to the smaller entrance pupil of the shorter lens. The smaller sensor will produce a noisier image with less dynamic range. At higher ISOs, this will degrade the resolution of detail.
If you hold the depth of field constant (often an important consideration for macrophotography), the smaller sensor will have the same size entrance pupil as the larger sensor. The smaller sensor will thus get the same amount of light, (per pixel and over the whole sensor) as the larger sensor. Here the dynamic range and noise should be similar for the two cameras.
