# Canon Mark IV Not Reading Memory Card



## kitkatdubs (Oct 28, 2018)

I have been shooting with my Mark IV for about 2 years now and just recently been having a weird problem.

I will shoot with the card and fill it up.  Once I have no images left available, I take it out and put a new one in.  However, when I put the new one in, the camera does not turn on right away and let me begin shooting.  I usually have to take the battery out, put the battery back in and try that until it will read the card and I can start shooting again.  Does anyone know why it would be doing this and if they have also had this problem?  I don't remember it ever doing this when I first bought so just wondering if I may have something wrong with my camera.


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## bratkinson (Nov 4, 2018)

I don't know about the 5D4, as I have the 5D3.  I try to remember (at 71, my memory is slipping too fast) to turn off the camera before removing a memory card.  Part of that habit is due to a known issue on computers when removing a USB memory stick without properly 'ejecting' it to finish writing whatever may be getting written.  The other part is the possibility of electrical surges/spikes/sparking causing damage at the moment the circuit(s) is/are broken.  

Computers, and your camera as well, have an internal 'buffer' that can quickly store image data and then write it out to the memory card(s) as fast as they can accept the data.  I don't use my camera for videos or even 5-7 frames/sec 'stop action' videos, both of which tax the limits of the camera and the memory card to transfer data.  Considering the image sizes (mega pixels/mega bytes) produced by a 5D4, you'll want the fastest memory cards you can find.  These days, most software (including Windows, etc), and camera firmware, will empty the buffer and write out the data as soon as it can to eliminate any loss of data.  While it may be reasonable to think it can get it all done in 0.5 - 2.0 seconds, give or take, there may be situations where the memory card has a problem that requires multiple attempts to successfully write the data.  The camera will 'retry' it a preset number of times and may or may not 'give up' on that storage address and store the data at the next available address.  How many times it retries and/or marks that address 'bad' and writes to another, I have no idea.

So, perhaps the issue is your camera is still actively writing data to the memory card(s) and you open the door and pop it out.  If it isn't done writing, I'd expect the last image or images on the memory card will be only partially recorded and may not be readable on your computer or even back in the camera.  Assuming (I know what 'assume' means) the camera was actively writing to the memory card and you popped it out, the firmware is 'waiting' for a response from the memory card that the data has been written successfully.  ALL read and write operations in computers and cameras are two-way conversations so when the write (or read) is physically completed, a 'finished' message is sent to the computer by the device.  Without that 'finished' message, the computer or camera will simply wait and wait until the cows come home.  Modern computers can have 100s of tasks processing, so 'doing nothing' until the 'finished' message arrives is actually the computer working on other tasks and when 'finished' arrives, it will resume whatever task was doing the reading/writing. 

Choice "B" - Part of me also thinks that it might not be the last frame(s) you took and ejected the card.  Instead, it could be a card that you did that on previously, and as a result, the 'directory' of what is where is incomplete or damaged.  So...try reformatting all your cards *in the camera.*  That may solve your problems.  For what it's worth, before going out on a shoot, I reformat all the cards I'm taking with me.  That way, I know the card is empty and should function as expected.

Of course, choice "C" is it could be you have a bad memory card that needs replacement, too.


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## jcdeboever (Nov 5, 2018)

I know Fujifilm doesn't like cheap cards. I use SanDisk Extreme Pro cards and buy them from reputable dealers. I only format them in the camera. With the Fuji cameras, they will do weird stuff like your experiencing. Make sure the block is fully in the unlock position.


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## john.margetts (Nov 5, 2018)

As Bratkinson says, I would always turn off the camera before removing the card. These toys are expensive and it is not worth ruining them for the sake of one second's effort.

My EOS 80D's manual says to turn power off before opening the card cover - and wait for the access lamp to be off as well.


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