iMac won't read SD cards

No, you're not the only one, there are several of the same type threads going on. Fortunately (for me) I don't have this problem. I found this

I put the card in the slot, but it did not mount. What should I do?

Remove the card and insert it again. Sometimes, if you put the SD card into the slot too slowly, it may not mount properly.

On this page, give it a look.

http://support.apple.com/kb/HT3553#2

And I found this

http://support.apple.com/kb/PH4460

Is it even possible to insertthe card in the wrong orientation? I'd have to go to my office where my iMac is to try and right now having morning coffee I'm too lazy to do that.

In another thread about this not seldom problem, I read someone stating that he sprayed a little bit contact spray into the sd slot, and after that the sd card was read OK everytime. ?!😮

Run software update to see if anything needs to be brought up to date. Have you tried insertingthe card and starting Disk Utility to see if DU recognizes it?

Never meant to imply that you didn't know your way around.....you camera choice and the fact that you use aperature led me to believe otherwise :-)

Have you tried resetting the SMC? I'm out of ideas after that.

I've had the same issue for a while. Stumbled accross something that worked for me by accident.

Leave the SD card in the slot and restart your computer. When it boots up again, it should automatically be mounted.

have just experienced the same problem, my imac is only 4 months old!! after sitting on the phone to Apple support for half an hour then running through a whole lot of techy rubbish that didn't help the situation, I was put onto a "senior support officer" (almost an hour and a half later) only for him to tell me I need to MOVE closer to a city to get a technician to come and help me. I was quite relaxed and obliging until this comment lol perhaps their resellers need to have a bit of technical/service training provided. anyways enough of my rant, I decided to investigate further myself, tried a few things others had suggested, then tried your way...tadaaaaa there it is THANKYOU Mt.Osc!!!!!!!! wish I had've read this 2 hrs ago!!!!!!!!!

http://cvil.ly/2011/10/30/imac-sd-card-reader-fix/

I think Apple's fix for this is shown in the new iMac design:

Put the SD card slot on the rear of the computer where nobody will want to use it. Reported problems with the computer not reading SD cards will drop dramatically. Problem solved.

(LOL....sorry....couldn't resist).

I have the same problem. I tried EVERYTHING, Verifying the disk, resetting the PRAM, rebooting with the SD card in the slot, rebooting without the SD card in the slot, full power down with unplugging the power for minutes, and the best I get is one SD card will mount with a reboot, but the images all are locked (there is a lock icon next to each image) and once you eject them correctly, you still can't mount a second SD card until you reboot with the new card in the SD slot.

This is definately an widespread and longstanding problem with the SD slots on multiple Apple computers (desktop, laptop), which has not been addressed. This is especially frustrating becuase I purchased a Mac specifically for the editing, managing, and publishing of my photography. I'm now hampered by not having a functioning SD card slot. 😠

I'm having the same problem with a new (late 2012) iMac. One SD card reads fine, another only reads when I re-boot??? The one that doesn't work is a SDHC UHS-I. Very strange and irritating.