Are long exposure RAW files larger?

[nickzou]

Okay this might be a really stupid question but I was thinking about uses of RAW files. Since the shutter is open longer, sometimes by several factors, does that mean the sensor is collecting more information over a longer period of time? Doesn't that mean the files should be larger? If not, what am I misunderstanding about RAW?

 

[KmH]

No doubt, content affects file size.
Take a photo of a blank section of wall, then turn and take another photo of the room. The photo of the room will be a larger file than the file that is the photo of the blank section of wall.

 

[480sparky]

Okay this might be a really stupid question but I was thinking about uses of RAW files. Since the shutter is open longer, sometimes by several factors, does that mean the sensor is collecting more information over a longer period of time? Doesn't that mean the files should be larger? If not, what am I misunderstanding about RAW?

Shooting raw does not affect your exposure time. Why do you think the shutter is open longer?

I can't see any reason why an exposure taken at 1/60 would differ in size from the same scene shot at 15 sec with a 10-stop ND in front of the lens.

 

[jedirunner]

So I know nothing about photography, but am enjoying starting to come up to speed. But one thing I know is technical junk (20+ years of computer programming here) ... So, raw files capture all the detail of the sensor, but then that data, as it's stored in a file, is compressed. Otherwise the file would be even larger. You don't lose any of the information (unlike some compression schemes which lose some data). But it is compressed. So depending on the types of data in the image (mostly, the variety in the image), the file may be slightly larger or smaller. Shouldn't be a big difference, but a difference nonetheless.

As an example, (this is not how raw files actually work, but a very simplistic example of how compression could work), instead of the camera storing 15 pixels worth of "black" data, repeating much of the information for each pixel, the camera could store it like this "15 pixels of this specific color code", which potentially could be much smaller. Now the formula it uses is far more complex than that, but I think that gives an example of how something *can* be compressed and not lose any data, and how the actual image data can affect the raw file size.

Now, how that all relates to exposure settings ... (which as a total noob to photography I don't understand yet) ... well, if that causes the image to have more variation in the individual pixels of data, then depending on the formula to store the data, the file could potentially be larger.

As a caveat, some cameras don't compress the raw (to my understanding), and others do.

Here are some links with more info on raw files:

• Understanding RAW Files Explained
  
• http://www.luminous-landscape.com/tutorials/understanding-series/u-raw-files.shtmlTutorials – The RAW File Format
  
• http://www.cambridgeincolour.com/tutorials/RAW-file-format.htmRaw image format - Wikipedia, the free encyclopedia

Kevin

 

[480sparky]

So what does shutter speed have to do with it?

The certain amount of light will strike a given pixel if the shutter is open for 1/60 sec. Put a 10-stop ND filter in front of the lens, and you've cut the amount of light by a factor of 1/1024 ( 2 ^ 10). So you increase the exposure by the same factor, open the shutter for 15 seconds, and the same amount of light will reach that pixel.

How much compression the camera does after that is not affected by shutter speed either.

 

[Crollo]

Shooting raw does not affect your exposure time.

Try reading a little more carefully.

Since the shutter is open longer, does that mean the sensor is collecting more information over a longer period of time?

Raw contains more information therefore it would make sense that raw would make better use out of the extra information that the sensor provides. RAW would\should be larger then JPG no matter what exposure length your using, because it has more information regardless of what you're taking a picture of.

 

[jedirunner]

If there's truly no difference (in the actual per-pixel values of light data) in using a filter with that shutter speed compared to the exposure settings mentioned, then the file should have no difference. The same data run through the same compression formula should give the same result every time. But if there's anything different in any of the pixels in the per-pixel data, then the data coming out the compression formula will be different.

I don't know (yet -- maybe in a year -- man that seems like forever right now) how x-stop filters with different shutter speeds compare to exposure can effect the light entering the camera ... or if any individual pixels will be different. For that type of conversion information, I humbly bow to all of you. I can only comment on the tech side of things.

Kevin

 

[480sparky]

Try reading a little more carefully.

Try it yourself.

Okay this might be a really stupid question but I was thinking about uses of RAW files. Since the shutter is open longer, sometimes by several factors, does that mean the sensor is collecting more information over a longer period of time? Doesn't that mean the files should be larger? If not, what am I misunderstanding about RAW?

Again....... shooting in raw has - n o t h i n g - to do with the shutter speed.

 

[Crollo]

My bad, fell on my sword.

To answer his question, no. As KmH said, if you take two pictures of a wall that are the same, the filesize isn't going to change because it's the same content, regardless of however much information was gathered to make that image.

If you however take two images in RAW and JPG that are the same the raw will be larger always, because it contains far more dynamic range and information.

 

[MrSleepin]

i switched from shooting in jpeg format to RAW... and i am NEVER going back! RAW is a life err....image saver!

and to answer your question... no.

my raw files range from 7-10mb per pic (at 10mp) and the jpeg's are usually 3-5mb each. totally worth it to shoot in raw!



lemme just give you a quick few reasons why it's a life saver....

if you shoot with the wrong white balance settings....you can fix it, and no one will ever know that it was shot wrong.
if it is under/over exposed, it can fix that too! (not so much if you have some white hot spots, those are tricky)
if your colors look a little dull... you can fix the color's vibrance!

best way to compare jpeg to raw, take 2 of the same pic, and try editing them both.

this was a good thread describing what i mean....
http://www.thephotoforum.com/forum/...ges/255924-raw-v-jpeg-shootout-challenge.html

 

[nickzou]

I guess the way I thought about it was, the sensor collects data at a rate of Xmb/s if you leave the shutter open for say 4 seconds compared to 1/60 of a second because of the rate at which the sensor gathers the data.

 

[MrSleepin]

the sensor collects light, not bytes of information... the size of the image file depends on what all is there, in the image...

 

[enzodm]

I guess the way I thought about it was, the sensor collects data at a rate of Xmb/s if you leave the shutter open for say 4 seconds compared to 1/60 of a second because of the rate at which the sensor gathers the data.

It collects photons, with an upper limit. You are doing long exposure only if photons are rare (i.e., dark).

 

[PDP]

It collects photons, with an upper limit. You are doing long exposure only if photons are rare (i.e., dark).

Exactly - A well exposed image contains roughly the same amount of information (from the photons which strike the sensor). In low light it just takes longer to collect all that information due to a lack of photons.

 

[adversus]

I just checked a few RAW images I had on my desktop (Nikon NEF). They range in size from 16-18mb in size (these images in question are a dark room with a single off camera light source), so yes, the exposure of a photograph (i.e. slow shutter vs. fast shutter) will change it's file size.