Compact Flash or SD Cards??? Which is better and why?

PhotographyJunkie · May 21, 2013

I just purchased the Canon 5D Mark iii and there are is a slot for the compact flash AND SD card. I'm accustomed to using the SD card but want to know if there is a benefit to using the compact flash card or are they the same quality, etc? Thank you for your feedback.

JohnTrav · May 21, 2013

I only use compact flash since that's all my 7D will take.

IMO it really comes down to what you are going to shoot. If you just shoot for fun then I would save the money and get some SD cards. If you are serious and have paying jobs I would buy CF cards with good write speeds and also get name brand ones for reliability purposes. I use transcend and sandisc and have yet to have a problem with them.

Check this link out from adorama for more info. Hopefully it helps.

http://www.adorama.com/alc/0012945/article/Memory-Myth-Buster

Mike_E · May 21, 2013

If you drop and then step on a CF card you are a lot more likely to be able to retrieve your photos.

Just sayin.

DanielLewis76 · May 21, 2013

You also need to consider what you will be putting the card in to to get the pictures off. My Macbook only has an SD Card slot for example.

TCampbell · May 21, 2013

Although SD cards have been getting faster, the main reason high-end cameras used CF cards was for performance. CF cards could have a transfer speed of around 100MB/sec sustained (not burst). CF cards are lower cost technology but used to only be able to sustain a max of maybe 10MB/sec. They come a long way and many cards are faster than 10MB/sec. They've even got a class called "UHS" which can transfer at speeds up to 312MB/sec HOWEVER... while the card will only get that speed if it's used in a device that has a UHS compatible SD slot (the 5D III does _not_ have a UHS slot.)

That means you'll get faster transfer speeds if you use the CF card.

BUT... a more important question is: should you even care?

Transfer rates are for people who are using the camera in "continuous" or burst shooting mode... usually sports or action. The camera has an internal memory buffer. As you shoot, the image first goes to the camera's internal memory buffer, where it can queue up to wait for saving onto the memory card. That buffer will hold quite a few shots before it's full (the number of shots depends on if you're shooting RAW vs. JPEG. It will hold considerably more JPEGs before it's full.)

Take a look at the following tables: Canon EOS 5D Mark III Review: Digital Photography Review

The 5D III, in continuous mode and writing to a CF card, is able to shoot about 17 images before the frame rate gets a severe cut because the buffer fills and then it can't shoot any faster than the transfer speed to the card.

If you switch to JPEG (still using a CF card), there is no limit... it can shoot at continuous burst until the card is full. That's because JPEGs are small enough and the camera's write speed to a CF card is fast enough that the camera can always transfer data faster than it can shoot... so there will never be a bottleneck.

Now switch to SD card and it's a different story. The RAW continuous mode can only shoot 14 frames before it slows down. That tells us that when we used a CF card, at least 3 images transferred to the card making room for more images before we hit the limit back at 17. But since SD cards aren't as fast, it can't transfer as many images, hasn't re-claimed as much internal memory buffer space so you hit the brakes after 14 frames.

Still with an SD card, switch over to JPEG (max resolution and quality mode JPEG) and you instead of unlimited shooting (like it was with the CF card) you can "only" shot 42 images before it hits the brakes.

So the real question is the following: Do you see yourself putting your camera into continuous shooting mode and shooting more than 14 RAW images in a row -OR- more than 42 JPEGs in a row?

If the answer to the above question isn't "yes", then it doesn't really matter which card you use... you would never encounter the buffer limits so there no real difference to you.

I have both cards loaded... but honestly, the MAIN reason why I might shoot with my SD card (over the SD card) is that when I travel, my laptop and iPad can both import images directly off an SD card, but I don't have a CF card reader that I travel with (that's only on my desktop computer back at home.) So there's a convenience due to the fact that more devices tend to have SD card slots built-in.

If you're a sports/action photographer, then there's a strong case for why you might prefer JPEG... especially JPEG to a CF card. You basically never encounter buffer limits when shooting.