Formatting SD card as FAT16 under Mac OS X

I recently purchased a Columbus V990 GPS logger so that I could geo tag my photos. The V990 supports 4GB SD cards. Interestingly, it can read SDHC cards, which would seems to imply that it should be able to support up to 32GB. After digging a bit deeper into the specifications, the limiting factor is due to the V990 supporting only FAT16 file system formats.

The Disk Utility GUI in Mac OS X cannot format SD cards with FAT16. Only FAT32 appears to be supported. In order to format a card as FAT16, you will need to use the command line version of Disk Utility, diskutil, and the BSD command line tool newfs_msdos.

The first step is to get the SD card mounted, which usually involves inserting it in your card reader. Once this is done, you will need to find out the device name that is assigned to card. So run the following on the command line:

bash-3.2$ diskutil list

/dev/disk0

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                        *1.0 TB     disk0

   1:                        EFI EFI                     209.7 MB   disk0s1

   2:                  Apple_HFS Macintosh HD            999.3 GB   disk0s2

   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

/dev/disk3

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:     FDisk_partition_scheme                        *8.0 GB     disk3

   1:                 DOS_FAT_32 GPS_LOGS                8.0 GB     disk3s1

In my case, the SD card is at /dev/disk3. Now we just need unmount the device:

bash-3.2$ diskutil unmountDisk /dev/disk3

Unmount of all volumes on disk3 was successful

The next step is to run newfs_msdos and indicate that we want to create a FAT16 filesystem:

bash-3.2$ sudo newfs_msdos -F 16 /dev/disk3

newfs_msdos: warning: /dev/disk3 is not a character device

512 bytes per physical sector

newfs_msdos: warning: sectors/FAT limits sectors to 4194721, clusters to 65534

newfs_msdos: warning: FAT type limits file system to 4194144 sectors

/dev/disk3: 4193536 sectors in 65524 FAT16 clusters (32768 bytes/cluster)

bps=512 spc=64 res=1 nft=2 rde=512 mid=0xf0 spf=256 spt=32 hds=255 hid=0 drv=0x00 bsec=4194144

After remounting the SD card, you will notice that the capacity is only 2GB, a bit short of what the V990 is supposed to support. In order to increase the capacity to 4GB, we need to increase the number sectors per cluster to 128: 

bash-3.2$ sudo newfs_msdos -F 16 -c 128 -e 1024 /dev/disk3

newfs_msdos: warning: /dev/disk3 is not a character device

512 bytes per physical sector

newfs_msdos: warning: sectors/FAT limits sectors to 8388929, clusters to 65534

newfs_msdos: warning: FAT type limits file system to 8387776 sectors

/dev/disk3: 8387072 sectors in 65524 FAT16 clusters (65536 bytes/cluster)

bps=512 spc=128 res=1 nft=2 rde=1024 mid=0xf0 spf=256 spt=32 hds=255 hid=0 drv=0x00 bsec=8387776

This gives us a 4.29GB FAT16 filesystem, with 1024 files per directory, which is useable by the V990.

VR Light Leaks with Nikon 24-85mm AF-S

There are two main advantages to taking star trail photographs during the winter: 

1. The air is colder, which can result in clearer skies. 
2. The sun sets much earlier. Often as early as 4:00pm for me. Taking photographs is a far easier endeavour in comparison to the summer when the sun sets at 9:00pm and good exposures are only possible after 12:00am.

There are two main disadvantages to taking star trail photos during the winter:

1. The air is colder and it can get down right freezing!
2. Winter often brings more precipitation, which results in more clouds, which results in less stars.

During a recent trip to Harrison Hot Springs, I was lucky enough have clear skies. So I took the opportunity to photograph the stars. My setup was a Nikon D600 with the Nikkor 24-85mm AF-S lens. After taking some initial test shots, I noticed a light leak at the bottom and lefthand side of the frame: 

Harrison Lake, facing North (24mm, f/3.5, 30sec)

With my DK-5 finder on, I initially thought that the leaks might be the artificial lights that were to my left and right.  I placed my lens hood on, but still observed the same amount of light leaking into the 24-85mm. I decided to recomposed, just to see if something would change:

Harrison Lake, facing NNW (24mm, f/3.5, 15sec)

Same amount of light leak, and in the same location in the frame. I tried various things, including using my toque to cover up various parts of the camera and lens.  After about an hour, clouds were beginning to approach, so I decided to use my 35mm 1.8 AF-S (DX, not the new FX version) to salvage what I could of the evening. 

When I moved to a warmer location, I spent some time experimenting with the Nikkor 25-85mm to see what was going on. I had used this lens for star trail photography before, so these light leaks were a bit of a surprise. I tried various experiments, including placing the lens cap on the lens and taking the exposure in a light-tight box, but I would continually get something like the following:

Light leak with lens cap on (f/3.5, 30sec)

This was very odd, considering that the surrounding light was changing during my tests, but the light leak remained the same. I suspected that the focus window on the lens was leaking light, and I even used a flashlight to help track down the leak on the camera/lens, but again, the exposure remained the same. The only thing that caused the light leak to change was zooming the focal length to 85mm:

Light leak at 85mm (f/4.5, 30sec)

Since the light leak always remained the same, all I could think of was that the camera itself was generating some kind of light internally (the view screen? the status LED? the LCD screen?). After doing some in-depth searching on the web, I came across a post on Luminous Landscape where someone theorized that the VR in lenses might be using lasers. I turned off the VR and voila, the light leak was gone:

Light leak gone! (24mm, f/3.5, 30sec)

I felt silly that my VR turned on the entire time, considering that I shouldn't have had VR turned on when my camera in mounted on a tripod! Time to create a preparatory "checklist" for my star trail photography. For those that are interested, here's a photograph taken with the 35mm 1.8 AF-S on the D600:

Nikon D600 with the 35mm f/1.8 AF-S (f/8, 30min)

Cheers!