Are long exposure RAW files larger?

[brush]

There seems to be a lot of confusion here because the OP combined 2 completely unrelated factors into a single question. If you split it out the questions are a lot easier to answer.

1) Does a long exposure create a larger file size?
NOT for the sake of long exposure, but if it happens to catch more detail than you would've caught at a short exposure, then yes it will. A properly exposed image will be a larger file size than an under or over exposed image because blown out areas are all going to be a solid color and therefore take less memory to recreate. Your image sensor doesn't capture time, it captures light. The shutter speed just gives the light time to be captured. If you expose too long, you'll have a completely white image and that's going to be a significantly smaller file size than a properly exposed shot.

2) Does a RAW image create a larger file size?
YES. When you shoot in JPG all the in-camera processing that happens to your white balance, contrast, saturation, yadda yadda yadda get applied to the image and compressed down to JPG format. As a jpg the only thing the image file is telling you is "this pxel is 003399 and this pixel is 188f24". That takes a whole lot less memory than "This pixel is 003399 and has been modified by the camera settings to have its contrast decreased to -40, saturation set to +10, white balance at 5700, and is now being displayed as 002983. However an artistic filter applied in-camera has created vignetting that darkens it to 002525." When you do it for 18 million pixels, all of a sudden that detailed calculation a RAW file puts into each pixel makes for a significantly larger file than a JPG. Think of RAW as a photoshop file with tons of layers on top of the original image, each layer modifying how it looks...and you can go back & change each of those layers as you see fit. With a JPG you just have 1 flat image, and to change its appearance you have to modify pixels. All that "layer" data is why a RAW file is larger, has nothing at all to do with shutter speed.

Combining the questions together like the OP did just confuses issues because the 2 parts are unrelated. If a RAW file is properly exposed (whether a slow shutter is used or not) it'll be a larger file than an under-exposed RAW file because it contains more data to recreate the details of the scene that would otherwise be lost in shadows. Same holds true for JPG vs under exposed JPG. The only reason a properly exposed RAW file is larger than a properly exposed JPG file is because of the extra detail it provides beyond just "this pixel is blue."

And in case all my rambling lost the other key point...shutter speed has no direct effect on file size, image sensors don't capture time. All they capture is the voltage reading of the light that hits it. If it's open long enough to make that pixels light reading say blue, it records blue, if its open long enough for it to say white, it says white. It never says "being exposed for 25 seconds caused me to believe this blue thing was white."

 

[Buckster]

I don't think 2) was even in question at all, even for the OP.

In any case, I think question and all relevant answers have been well beaten to a pulp and thoroughly explained already.

 

[KmH]

A JPEG is a smaller file size because it is an 8-bit depth file, while the Raw after initial conversion is a 16-bit file.

JPEG is called lossy because of that 16-bit to 8-bit reduction in the bit-depth. The vast majority of that reduction is accomplished by discarding about 80% of the color information extrapolated during the Raw file demosaicing process. The rest of the file reduction comes from converting the pixels into 8x8, 8x16, or 16x16 pixel units known a Muinimum Coded Units (MCU's).

 

[Helen B]

There is a lot of confusion here.

The Raw image data inside a Raw file contains data for only one channel per pixel: luminance. There is no RGB data for each pixel. That is worked out later during demosaicing.

Take the D3 as an example. There are 12,052,992 pixels. If you shoot in uncompressed 14-bit Raw you need two bytes per pixel (ie 16 bits, because storage usually works in bytes, not bits). That means about 24 MB* (M for mega, B for bytes - m is milli, b is bits) file size. That is the approximate file size you get in uncompressed Raw, whether it is the most detailed image imaginable or pure black. Two bytes per pixel**.

Along with the pixel luminance data, the Raw file also contains a low res preview JPEG (even if you do not specify Raw + JPEG in the menu) along with the metadata. The different sizes of preview JPEG mean that the uncompressed Raw files can have slightly different sizes. For example: 24,125 kB for a detail-less black image with only noise vs 25,209 kB for a highly detailed image - the size of the embedded preview JPEG is the only difference, the metadata is identical (both shots taken with identical all-manual settings).

Once you compress the Raw files, even losslessly, the file size can change in the same way zipping doesn't achieve the same compression on different files. In the above example, the losslessly compressed file size varies between 11,419 kB for the detail-less image and 14,242 kB for the detailed image. In this case the changes are because the possible degree of lossless compression is greater for the detail-less image than for the detailed image, as well as the (same as above) small difference in the size of the embedded preview JPEG.

Neither the Raw file nor its associated sidecar file (if it has one) needs to hold information about changes to individual pixels. Most of it, like contrast, saturation, white balance, camera profile etc are applied globally, so only those global decisions are stored. This takes a tiny amount of space in comparison to the pixel-by-pixel luminance data.

*Remember that when discussing file sizes the difference between mega and mebi, kilo and kibi are often ignored, but they can account for apparent anomalies.

**This is not a hard-and-fast rule. Cameras can use fewer than two full bytes to store 12- or 14-bit information.

 

[unpopular]

not to mention that all of those are really bad reasons to shoot raw...

That's a bit subjective.

I suppose they're good reasons if you don't know how to use a camera :er:

 

[nickzou]

Also kinda related. Again, probably due to my lack of understanding of RAW files. If RAW continuously collects data, if you overexpose and image, like.... REALLY overexpose, is it possible to recover it to the point of proper exposure? I mean, all that data is still there right? Say it takes 1/40 of a second to properly exposure the shot, but leave the shutter open for 2 seconds, can you... theoretically ditch the excess data and find the image at it's proper exposure somewhere in the RAW data?

 

[480sparky]

Also kinda related. Again, probably due to my lack of understanding of RAW files. If RAW continuously collects data, if you overexpose and image, like.... REALLY overexpose, is it possible to recover it to the point of proper exposure? I mean, all that data is still there right? Say it takes 1/40 of a second to properly exposure the shot, but leave the shutter open for 2 seconds, can you... theoretically ditch the excess data and find the image at it's proper exposure somewhere in the RAW data?

Not really. Blown out is blown out. Once the pixel reaches a certain point, the data is recorded as pure white (255:255:255). If the portion of the image was purple, or pink, or yellow..... it will still be recorded as white. "Ditching excess data" will only render that pixel gray, depending on how much you want to get rid of.

 

[analog.universe]

Also kinda related. Again, probably due to my lack of understanding of RAW files. If RAW continuously collects data, if you overexpose and image, like.... REALLY overexpose, is it possible to recover it to the point of proper exposure? I mean, all that data is still there right? Say it takes 1/40 of a second to properly exposure the shot, but leave the shutter open for 2 seconds, can you... theoretically ditch the excess data and find the image at it's proper exposure somewhere in the RAW data?

I think the confusion here results from a misunderstanding of how the data is actually collected. The entire time the shutter is open, nothing digital is happening... The sensor is zeroed, the shutter opens, light begins falling on the sensor. Photons are converted to electrons and begin to accumulate in each of the individual pixels. They may accumulate for 1/500 of a second or for many minutes. When the shutter closes, only then is that pile of electrons (voltage), converted from analog to digital, and it happens nearly instantaneously, from the photographers perspective. So no matter how long the shutter is open for, the data that makes it into the raw file is all collected in the instant the shutter closes, and only represents the voltage at each pixel. It contains no information about how the voltage at that pixel changed over time. (Because reading the value at a pixel requires destroying it). Hope that clarifies....

 

[manaheim]

RAW is a dump of all information on the sensor, so time wouldn't affect it unless there was somehow more information on that sensor as a result. (think in terms of taking a picture of a skyline in the dark. The longer you keep the shutter open, the more is exposed, the more data you get)

Variation in size typically comes from a lossless compression on the RAW data, though some cameras are capable of lossy compression (though I can't imagine why you'd do that to a RAW file)

Without that compression RAW images should, in theory, be all the same size.

 

[EchoingWhisper]

The higher the ISO, the larger the file.

 

[enzodm]

The higher the ISO, the larger the file.

No. You may observe some variation due to more noise (that when compressing is like having random information, which is hard to compress), but is due to noise, not to ISO.

 

[manaheim]

The higher the ISO, the larger the file.

Can I report people for posting misinformation? God that would rock.

 

[rokvi]

OK, I understand that it doesnt matter the length of exposure if the "detail" is still the same in pixels then it will roughly be the same size, however what DOES happin in post processing if you raise the exposure value does that make that file size bigger?

 

[EchoingWhisper]

The higher the ISO, the larger the file.

Can I report people for posting misinformation? God that would rock.

If you can, report as you wish. It is just my observation that pictures with higher ISO are larger.

 

[enzodm]

If you can, report as you wish. It is just my observation that pictures with higher ISO are larger.

You are observing the wrong variable. Try to take a 3200ISO picture with lens cap on .