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

[–] Toldry@lemmy.world 6 points 9 months ago* (last edited 9 months ago)

y'all are delightful

[–] shneancy@lemmy.world 5 points 9 months ago (1 children)

wow I might have to try it! I love macro photgraphy :D

[–] miss_brainfarts@lemmy.blahaj.zone 2 points 9 months ago* (last edited 9 months ago) (1 children)

You could just get a reverse-ring to mount one of your existing lenses backwards, but I want to steer you into the rabbithole of vintage lenses anyway

Ebay has loads of all kinds of them, and many are in no way behind modern lenses in terms of image quality, while being super affordable.

But then there's also lenses people specifically seek out because they aren't perfect, and exhibit visual quirks that make them interesting for creative work.

The soviet Helios 44-2 for example has some strong spherical abberations going on, producing what most people call a „swirly bokeh“.
This lens has been used in some scenes of The Batman, and they even modified their expensive anamorphic cinema lenses to look more like the Helios.

[–] shneancy@lemmy.world 3 points 9 months ago (1 children)

ouuuu, I do love playing with how my photos look like before the light even reaches the sensor. I think one of my friends once got himself an old soviet lens, I'll have to ask him about how it shot

[–] miss_brainfarts@lemmy.blahaj.zone 2 points 9 months ago (1 children)

Another one I like a lot is my Pentacon auto 50mm 1.8 multi coating. If you can find one in good condition, this is a great looking lens you should be able to get below 50 bucks. At least that's the kind of price I remember last time I checked.

And it uses (like the Helios) the m42 screw mount instead of a proprietary bayonet. So that's a big plus for fans of open standards, even if it's absolutely irrelevant today, since you'll need adapters anyway.

But my favourite might be the Minolta Rokkor 50mm 1.4, that is just a nice lens. There's also a 1.2 variant, but it's harder to find and more expensive.

[–] shneancy@lemmy.world 2 points 9 months ago (1 children)

guess I'll need to start hunting for vintage lenses lol! I've only stuck to modern ones so far to expand my range but you're tempting me a lot with those comments :D

[–] miss_brainfarts@lemmy.blahaj.zone 2 points 9 months ago

Do it :D