So basically, a lens captures a large area of light and projects it onto a small sensor.
When you turn the lens around, it captures a very small area the size of the sensor it’s supposed to be used with, and projects an image into the camera that is way too large, resulting in what you see being a severe crop.
Which means, the shorter the focal lenght (and the further away the lens is from the camera, for example using bellows), the more „magnification“ you get out of this crop.
Now, this means three things:
You lose a fuck-ton of light, and since you’re required to close the aperture by a lot to get any kind of usable depth of field in such a configuration, you will sometimes not be able to see what the hell you’re even doing, because it’s so dark.
This is manageable with a 50mm lens, but obviously gets worse the more you crop.
Since you’re using old manual lenses, have fun with capturing a busy insect with all the right settings before it buggers off. Using continuous shooting and a flash that can keep up with it is invaluable.
And lastly, you can’t even use the focus ring anymore if you mount a lens backwards. Your focus distance is now fixed, and equivalent to the flange focal lenght the lens was built for.
This means your only way of getting the subject in focus is to move the whole camera back and forth, which gets increasingly difficult the higher your magnification, since the depth of field is so incredibly thin, even more so if you keep the lens wide open to see what you’re even doing.
But it’s fun, and so much cheaper than dedicated macro lenses :D
So basically, a lens captures a large area of light and projects it onto a small sensor.
When you turn the lens around, it captures a very small area the size of the sensor it’s supposed to be used with, and projects an image into the camera that is way too large, resulting in what you see being a severe crop.
Which means, the shorter the focal lenght (and the further away the lens is from the camera, for example using bellows), the more „magnification“ you get out of this crop.
Now, this means three things:
You lose a fuck-ton of light, and since you’re required to close the aperture by a lot to get any kind of usable depth of field in such a configuration, you will sometimes not be able to see what the hell you’re even doing, because it’s so dark.
This is manageable with a 50mm lens, but obviously gets worse the more you crop.
Since you’re using old manual lenses, have fun with capturing a busy insect with all the right settings before it buggers off. Using continuous shooting and a flash that can keep up with it is invaluable.
And lastly, you can’t even use the focus ring anymore if you mount a lens backwards. Your focus distance is now fixed, and equivalent to the flange focal lenght the lens was built for.
This means your only way of getting the subject in focus is to move the whole camera back and forth, which gets increasingly difficult the higher your magnification, since the depth of field is so incredibly thin, even more so if you keep the lens wide open to see what you’re even doing.
But it’s fun, and so much cheaper than dedicated macro lenses :D