
SD card is a type of memory card, which is used to store large amount of photos, videos, audios and other files. Standard SD cards are classified into three different types, i.e. SD cards, mini SD cards and micro SD cards. SD cards are available in different storage capacities like SDHC (Secure Digital High Capacity) and SDXC (Secure Digital Extended Capacity). SDHC cards can store 32GB of data whereas SDXC cards can store up to 2TB of data. SD cards use flash memory, which is non-volatile memory that stores data even when the power is turned off. Kingston, SanDisk, Transcend, Lexar and Patriot are popular brands of SD cards. SD cards are commonly used in many portable devices like digital cameras, camcorders, mobile phones etc. You can access the contents of SD card by inserting it in a SD card slot. Different models of Mac like iMac, Mac Book Pro have SD and SDXC card slot whereas recent versions of Mac mini have SD card slot. When you insert a SD card into SD card slot, your computer recognizes it as a USB storage device thereby you can easily access the files from the SD card. Generally, you can use only 32mm, 24mm, and 2.1 mm thickness SD cards in SD card slot but you cannot use SD cards whose thickness exceeds 2.1mm. SD card slot can also work well with SD card that exceeds 32GB and it also supports ExFAT file system.
SD cards are more commonly used in digital cameras to store photos and therefore there are more chances of photo loss from SD card. Photo loss may occur due to various reasons like accidental deletion using Command+Delete keys, improperly removing SD card from SD card slot etc. Generally, when you delete a file from Mac, it will directly go to Trash in which case you can undelete Mac Trash to recover the files.However, this is not applicable to external storage devices like SD cards i.e. you cannot find files deleted from SD cards in Trash. In few cases, you may accidentally delete a photo from SD card when it is connected to Mac OS through SD card slot resulting in photo loss. Therefore, before deleting any media files such as photos from SD card, make sure that the photo that you are deleting is not important to you.
If you have accidentally, deleted files from SD card on Mac OS then do not worry because there are chances of recovering deleted photos from SD card using Mac Undelete Software which is a Mac Undelete software to recover deleted files. But, to avoid permanent photo loss, don’t save or copy new files on SD card. SD memory cards have its own Trash, when you delete a photo from SD card it will be stored in .trashes folder from where you cannot restore them back until you use relevant recovery software. Mac Undelete Software is able to recover deleted photos from SD card, mini SD cards and micro SD cards. This software supports HFS+, HFSX, FAT16 and FAT32 file systems and can undelete files on Mac volume. The software also support recovery of various types of hard drives and hence helps to undelete Mac files from FireWire drives. Other than these devices, it makes iPod Shuffle music recovery on Mac possible.
To undelete camera pictures on Mac, you need to insert camera SD card in SD card slot then follow the below mentioned steps:
Step 1: Download and install the demo version Mac Undelete Software. When you run the software, the main window is displayed as shown in figure a.

Figure a : Main window
Step 2: Select "Recover files" option from the main window then from next window, select "Recover Deleted Files" to recover files that have been deleted or select "Recover Lost Files" to recover files that have been lost as shown in figure b.

Figure b: Select recover options
Step 3: Select the memory card and then click "Next". Select file types from next window; you can also skip this step by clicking "Skip" option as shown in figure c.

Figure c: Select file types
Step 4: The software starts scanning the SD card for deleted files. After scanning is complete the recovered files are displayed as shown in figure d. You can preview recovered files using "Preview" option to evaluate recovery results.

Figure d: View recovered files
Step 5: Select "Save Recovery Session" option to save scanned information. If you are satisfied with the obtained results then you can purchase the software. After purchasing the software, select "Open Recovery Session" option to reload scanned information and continue with the saving process.