Why isn't saving photos as TIFF files a popular choice by DSLR manufacturers?

Question

Why do many DSLRs have the option to save in RAW or JPEG but not in TIFF? It would be useful to save it as a TIFF file using lossless compression. It would be a midway between RAW and JPEG. Is it because the size of TIFF files is huge?

Answer 1

Noting other answers, and having had a bridge camera that did TIFFs, I'd suggest that for DSLRs TIFF is pointless except as an add on if it can be managed.

TIFF is a lossless way of saving an image, once an image is generated, BUT the image that it saves is an interpretation of what the sensor records.

RAW gives you the maximum possible flexibility in dealing with the available data. Software to convert to TIFF or JPG is provided by the camera maker plus the various commercial RAW converters are a small fraction of a good DSLR price.

JPG gives you user usable images at a compression level that suits the user.

RAW + JPG gives you all the advantages of RAW plus some of the advantages of JPG (as it usually does not allow selection of JPG compression level and the JPG provided may be not be the highest quality JPG the camera provides in pure JPG mode.
eg in a Sony A700, straight JPG comes in Extra Fine, Fine, Standard.
But with RAW + JPG, the provided JPG is "fine" and not "Extra Fine".

TIFF loses data relative to RAW and is far larger than any sensible JPG and has no great quality improvement over the best JPG. Once it is "not RAW" then it is subject to manufacturers decisions.

Useful where available is Compressed-RAW and Compressed RAW + JPG.
Available eg on Sony A700 but not on the newer A77 where it would be useful due to largr file sizes.
Compressed-RAW provides a lossless compression of the RAW file at the expense of processing time and a somewhat non-stanard format.

Answer 2

They do actually but not all of them. Even some bridge cameras can save as TIFF.

Unfortunately, TIFF was given a bad name because its files were huge. Early on, compression was not used for TIFF files by digital cameras and so that gave rise to the files being huge which also slowed down the camera considerably. One of my first cameras used to take 24s to save a single TIFF file.

You are right that it would be highly desirable to have a complete image out of the camera (rather than RAW data) but without compression loss and--equally important in my opinion--higher color-depth and dynamic-range than JPEG can store.

In reality any high-bit-depth file-format could do but camera makers do not see it as important yet. This will probably come as displays start showing more than 8-bits per channel and operating system support becomes more common (this exists already but in very limited numbers at this time).

Answer 3

1. Difference of file size between a lossless TIFF and RAW is not huge.
2. More time is needed to save a tiff than a raw, so to avoid delay in shots.

Jpg will also take more time due to the processing, but will have a significant file size reduction, hence jpg was used.

Answer 4

I own an Olympus Camera that has the three options you mention. Tiff files generated by the camera where somehow more than twice as big as the raw files.

My speculation here is that the RAW file, as it holds almost exclusively the information from the sensor has by nature less information to compress. That is, if the sensor where, say 10 bits per photosite, the RAW file would contain only this, arranged in a way that the conversion software will later decode knowing to which color channel each photosite corresponds.

To compose the TIFF file, the camera needs to calculate a pixel from several photosites, taking to account that some algorithms use a photosite several times to compute adjacent pixels. A pixel must be completed with its three channel values, if a 16 bit color depth image need to be encoded, you need tree values held by 16 bits each, thus you need 48 bits per pixel in the final image. Compare that to the 10 bits per photosite in the hypothetical sensor mentioned before.

Answer 5

RAW files are better than TIFFs in almost every respect:

• RAW files are smaller (as only one colour component per pixel is stored)
• RAW files capture more data
• RAW can be totally lossless (TIFFs don't lose data in compression but do in demosaicing)

The only disadvantage is the need to demosaic and process the images before they can be viewed. Which is where JPEG comes in. JPEGs are better than TIFFs in a number of respects:

• JPEG files are smaller
• There are lots of very cheap chips that do hardware JPEG compression. TIFF compression is marred with patent claims and doesn't to the best of my knowledge have the same hardware support.
• JPEG files offer almost the same level of quality, unless you push the files around in post, in which case you really really should be shooting RAW.

So this is why camera manufacturers mostly offer RAW + JPEG. It used to be the case that older bridge and compact cameras offered TIFF files, but this was before RAW conversion software was popular and most people lacked the ability to do the conversion, hence TIFF was offered if you really needed to avoid image compression artefacts.