# SD Cards effect quality?



## Sharpiks

Alright so some of you might have seen my thread about my Kingston issue. If so, I have two older SD cards that are one gigabyte and I think they're class two.

 I read somewhere before about SD cards and quality and someone told me that the size/class of the SD cards do not effect the quality of the photos but I beg to differ. With these cards, my photos are noisy and discolored. With my Kingston card though they were fine. 

 So do SD cards really effect photo quality, or not? What would of caused the photos to be noisy?


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## Boomn4x4

Sharpiks said:


> So do SD cards really effect photo quality, or not? What would of caused the photos to be noisy?


 
No, image quality is not effected. Digital images are recorded and stored as "digits", a series of 1's and 0's.

Simply put... When you take a picture, the camera converts the image into 1's and 0's... each 1 and each 0 making up a tiny component of the picture. Those 1's and 0's are then written to the card. When you look at the image on the disk, it restores what was originally recorded.

For data verification, the whole process uses what is called a 'check sum'. A check sum is a number. Immediatly before copying data, the computer (or camera) runs a mathematical formula on all of the one's and zero's that are in that image and comes up with a number, this is the check sum. The computer attaches this number to the file and then sends the file to the location where it is being copied. Once it gets to the SD card, the computer then reruns the formula on the 1's and 0's and checks it against the check sum. If the numbers match, the computer knows it was copied sucessfully, if they don't match, it knows that it didn't and it will retry to do the move.

As a very simplified example... if the image of a cat looks like "1011001". And you try to write it to an SD card it will run the digits through a formula... for simplicy, we'll say that 1=1 0=2... so it adds 1 + 2 + 1 + 1 + 2 + 2 + 1 and comes up with a check sum value of 10.... It adds 10 to the image and writes it to the SD card as. "10" - "101 001". Now as you can see, one of the 1's didn't get written. So after its written, it checks it against the check sum. 1+2+1+2+2+1 = 9... which doesn't match the 10. The computer knows that the image wasn't written again, so it rewrites it until it does.

Long story shot... its impossible for the image that was written to be any different that what was original recorded. It is impossible for the image to look different on different SD cards.

If that was the case, and it WAS possible for them to look different among differnt SD cards... you would also have to assume that the difference would also be noticable depending on it being stored on other media types. For example if an image looked different stored on two identical media types.... you would most certainly expect the image to look even more different if it was stored on non identical media types. If it looks different between two SD cards, image how much of a difference you would notice if you compared it between CD and SD, or SD and HD. No matter if you are using two SD cards, an SD card and USB drive, an SD card and a Hard Drive... the image will always look the same due to the media it is stored on.  For example, Take painting for example, if you were to paint a picture on a rock, and then another rock and then another rock, and make the claim that pictures look different if you paint them on different rocks.... If that claim was true, then you would expect to see even more of a difference in the picture if you painted it on a white wall, a stone wall, a piece of paper, and a beach ball.... but in the case of digital images, they always look the same no matter what you save it on.

This is not to say that the software or the hardware that was used could have screwed up those 1's and 0's some how... but if you notice a difference in image quality it is NOT because of the card.


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## cfphoto

Boomn covered it pretty perfectly. The only thing I would add would be that the speed of your card could affect how quick your camera right to the card, depending on the difference in read/write capabilities. This obviously does not have much to do physical  with image quality, but could affect your ability to capture the images you'd like if yor not able to capture what you want b/c of a slow card.


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## Sharpiks

I see.. Looks like I'll be searching for the reason of the noise then, thanks guys. :er:


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## Boomn4x4

Sharpiks said:


> I see.. Looks like I'll be searching for the reason of the noise then, thanks guys. :er:


 
When you get seemingly random defects, such as noise, software is usually to blame.  

When you get logical / linear defects, such as lines or bars accross the image, hardware is usually the problem.


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## Sharpiks

Boomn4x4 said:


> Sharpiks said:
> 
> 
> 
> I see.. Looks like I'll be searching for the reason of the noise then, thanks guys. :er:
> 
> 
> 
> 
> When you get seemingly random defects, such as noise, software is usually to blame.
> 
> When you get logical / linear defects, such as lines or bars accross the image, hardware is usually the problem.
Click to expand...

Software though isn't used, they're unprocessed and straight from the camera. There's no lines or anything.

Maybe shot in dark conditions, could a high ISO create a lot of noise?


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## Dao

> could a high ISO create a lot of noise?



Yes


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## Boomn4x4

Sharpiks said:


> Maybe shot in dark conditions, could a high ISO create a lot of noise?


 
Definatly.


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## Dao

Also high ISO + underexposed = even more noise


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## AlexL

What ISO are you shooting at? You need to adjust your expectation because the higher the ISO, the more sensitive to light it is, but at the cost of image noise. Even the best camera would have significant noise @ iso 6400.  Also, the higher MP to sensor size you have can also affect noise.


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## Sharpiks

I was shooting in low light conditions at an ISO of 800. A lot of pictures I've seen though that were shot at 800 don't have that much noise.

And besides I've shot at 800 before with a Kingston card and it wasn't as noisy.


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## Boomn4x4

Sharpiks said:


> I was shooting in low light conditions at an ISO of 800. A lot of pictures I've seen though that were shot at 800 don't have that much noise.
> 
> And besides I've shot at 800 before with a Kingston card and it wasn't as noisy.


 
Easy way to rule out the cards.... Copy the pictures from one card to the other.  If the card is the problem, the images that look good on one card will look bad on the other.  The images that look bad on the bad card will look good on the other.


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## Dao

The flash card is a *digital* storage device.  So 1000010101011001 is going to be 1000010101011001 when it store in card A or card B.

If there is a corruption on the data, you may have issue to display the image at all.  Not just degrade in image quality.


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## Judd

I don't know much about photography but I do know about PC's and am currently working on my A+.

What has been said about all those little 1's and 0's is right. All a digital file is, is a whole lot of 1's and 0's. And there are checks and balances to make sure every 1 and 0 gets placed.

I do not see how a card could make a difference. Digital is digital. Like said, whether it be a USB flash drive, a CD, DVD, or even a floppy disk, its all the same.

Digital media is not like paper where you have bond, matte, glossy, etc


Could you imagine the marketing campaigns that would be out if media determined quality?


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## Dwig

Sharpiks said:


> ...
> When you get seemingly random defects, such as noise, software is usually to blame.
> ....
> 
> 
> 
> Software though isn't used, they're unprocessed and straight from the camera. ...
Click to expand...


You're completely wrong. Software was used. The camera uses its own software to convert the sensor's RAW data into a digital file. It does sharpening, noise reduction, color enhancement, ... based on settings programed using preferences either hard coded or derived from user settings in the camera. Some cameras have better software than others.

Also, humans can't see digital files of any type. To see a digital image, software must be used to display that image on a monitor or to make a print. Such viewing or printing software is not all created equal. Some will do a better job of creating a display image than others.


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