[Eulogy]

Curious here - If I were to attain some m42 tubes, get a lens to attach to the end, and then use M42->K Mount as well as M42->EOS - Would there be any problems? Looking for a cheap solution for everyone in my family to take some easy macro shots without spending a fortune. (Basically, will there be any complications with this?)

[icywindow]

Nope, no problems.

Just a few notes:
Using extension tubes eats some light. Be prepared to use a longer shutter speed (or more light. A tripod is a good idea).
Make sure you get an EOS adapter with chip for focus confirm, as it's difficult to see what is in focus unless they have a focus screen.
The m42 lens may have an auto/manual lever. You can use that to figure out composition then flip the switch before you take the shot.

[Eulogy]

Thanks, glad to hear it will work. Cheap macro is awesome!

[jatrax]

Not sure if you mean to use on both K-mount and EOS. If only EOS then you do not need an M42>K-mount adapter, just M42>EOS. If you have both cameras then yes that is correct.

Complications? On k-mount, none that I can think of except everything will be all manual, but I assume you knew that. You will need to enable "use aperture ring" in the menu and then green button metering.

On the EOS, I think it should work depending on the adapter, but I am not familiar with EOS. Not sure how it will meter if the lens is unknown. Hopefully someone with Canon experience can help you with that.

[icywindow]

There's a Canon 7D in our family, so I've tried using two different adapters.
The unchipped adapter makes you work in manual mode, and it meters pretty much fine with the exposure meter.
The chipped adapter gains focus confirm and communicates a focal length back as well as aperture, so you can use Av mode. It will throw the EXIF data off. By default, it shows a FL of either 50 or 55mm and aperture of 1 or 1.4. There is a way to program these by a complicated set of instructions which has no confirmation except when you finish it changes the FL and aperture on the picture. I'd set it to the focal length of lens and keep the aperture at the default value.

I've tried so far a couple of fifties (Rikenon 55/1.4, Super Takumar 50/1.4 and Super Takumar 55/1.8) on extension tubes and they seem to work pretty well. My advice to myself is that when in doubt, stop down one more stop than you think it needs.

[newarts]

Both will work well. I agree that you should get a focus confirmation chip on the EOS adapter.

[RioRico]

Thanks, glad to hear it will work. Cheap macro is awesome!

EOS isn't covered, but let me recommend: https://www.pentaxforums.com/forums/pentax-lens-articles/152336-cheap-macro-b...lose-work.html