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JPEG Image File Format

This is to follow up a comment in another thread here -

(Jan 26, 2015, 10:03)EdMak Wrote:  I only shoot .jpg. Ed.

So do I.

There are many erroneous myths being perpetuated about JPEGs, particularly with regard to their editing, so that many newcomers are led to believe that they cannot be real photographers unless they shoot in a raw format.

Those myths are likely left-overs from the days when the computing power in the early digital cameras was minimal, and the speed and storage capacity of their expensive memory cards was very low, so that JPEG images contained little data compared with what modern cameras record. They were therefore quite low in image quality when transferred to a computer for displaying full-screen or for printing, and were prone to deterioration during any further editing and saving.

A typical example is my DSLR from a decade ago - its "high quality" JPEGs are rubbish by current standards. Its raw files contain less than half the data of the JPEGs from my modern DSLR. The only way to get decent images from the old DSLR is to process the raw files in computer software, when they can then be very good.

The are no such issues with my modern camera - the JPEGs are usually at least 10 MB of data, and are of very good quality. They can withstand extensive processing and still retain the capability to produce good prints up to A3, not that they usually need to, because they are of high quality out-of-camera, usually only requiring gentle and subtle tweaking at most.

There is no doubting the maths - there is more data in a raw file, so there is more latitude in processing raw files in computer imaging software, and for correcting mistakes that shouldn't have been made during shooting. But with a modern DSLR it is usually no longer necessary to shoot raw, unless you really want to.

There are some simple but important considerations when photography involves JPEGs -

Set the colour balance and exposure as close to correct as possible - which should be the aim also when shooting raw. (Although despite the myths to the contrary, white balance and exposure corrections can be achieved with high quality JPEGs.)
Study the histogram and, for most scenes except the obvious exceptions where there are no highlights, usually expose to the right, but make sure that important highlight areas are not over-exposed - (Highlight recovery is less effective in JPEGs.)

JPEG files can be edited directly in any imaging software, including Adobe Camera Raw!!
Always make a copy of the JPEG file, preferably into a separate folder, and process only that copy - always keep the original JPEG separately. (In some software, editing the original file and saving it will over-write the original.)
Before saving, ensure that the software is set up to save the JPEG file at the lowest compression, i.e. highest quality. (E.g. In PS Elements that is level 12.)
Finish the editing to your satisfaction before saving, so that the edited JPEG file is saved only once. (Repeated saving of a JPEG reduces its quality slightly each time.) Alternatively, if you want to carry on editing the file later, save it in a non-compressed file format (E.g. as a TIFF, or in Photoshop's own PSD format.) and convert it back to JPEG when finished.
If you need to resize a JPEG file, e.g. for the Web, do that only after all other editing is completed.

Most cameras now have the option to save each image in both JPEG and raw formats (Raw+JPEG). That is what I used to do, until I found that the raw file was, literally, a waste of space when using a modern DSLR.

But, as always, "To each his own"! (Edmak)


Raw has greater dynamic range than jpg. JPEG records 256 levels of brightness, and RAW records between 4,096 to 16,384 levels! This is described with the term “bit”. JPEG captures in 8bit, and RAW is either 12bit or 14bit.

With that extra data you can adjust under/over exposure to a greater degree.

You can adjust whiteblance and temperature to a far greater degree without causing clipping. Adjust a jpg and a raw file white balance, then look at the histogram.

The loss of data with a jpg is not just when you create it, every time you edit it and hit save, you lose data, even with the compression setting set to max quality.

The downside to raw is mandatory post processing, larger file sizes and slower shot rates.

I shoot raw for everything apart from sports or action, where I might need prolonged bursts to capture the action.


I have acknowledged here (and elsewhere) that raw files hold more data, giving more leeway for corrections and adjustments. However, in most cases the extra (excess) data is not essential when the image has been captured properly. The premium JPEGs from modern DSLRs still contain more than enough data for the processing needed to enhance them, without compromising the visible quality of the final result, when viewed normally rather than by pedantic pixel peeping.

Most of the examples quoted, to illustrate the benefits of using raw data, involve more extreme processing adjustments than I am suggesting here. They also often involve images resulting from errors that should have been avoided at the shooting stage, e.g. wrong white balance and wrong exposure. Nevertheless, and contrary to what many people think, JPEGs with serious mistakes can often be rescued to give a reasonable image.

E.g. This JPEG was shot with White Balance carelessly left on Tungsten from the previous night:

Processing that JPEG in first Adobe Camera Raw and then PaintShop Pro gave this image:

This is a 100% crop from the processed JPEG:

This is no work of art, but I think it would be a reasonable record shot to keep, if revisiting that historical location was not possible. Perhaps others could do better from raw data, but the facts remain - it was a silly error that I should not have made when shooting, and a correctly captured JPEG would have made a high quality photograph.



I agree totally. Good point well made!! (pixel peeping should be put on the Statute alongside peepers of the Thomas variety and summarily subjected to wearing Vaseline smeared glasses!)Big Grin

Kind regards


In photography, the smallest thing can be a great subject. The little human detail can become a leitmotiv.

—Henri Cartier-Bresson

Impressive Peter, get's the point over. Long time since I used a Kelvin Meter!!

Early P/S days, read one acknowledged P/S author, stated he had yet to find what he could not do in jpg, that could be done in shooting RAW.

When I changed Camera, about 2 years ago, found that CS4E, did not support the RAW Files, so just jpg, which I can open in RAW, does me fine. Ed.

To each his own!

(Jan 29, 2015, 13:29)Rolf Wrote:  .....pixel peeping should be put on the Statute alongside peepers of the Thomas variety and summarily subjected to wearing Vaseline smeared glasses! Big Grin

Big Grin Big Grin Big Grin

Cheers Rolf!

That's a fine discussion of JPEG and other files.


One of my fallback technical photo websites is called, I think, Cambridge in Color. But here's a link to their discussion of JPEG. And they mention a link to raw therein.

One of my conclusions, for now at least, is that it's nearly, or maybe totally, impossible to know what the camera's algorithms are to process the sensor, then create a file, then download a file. And equally difficult to know what all the editing and file conversions and file saving does.

You should see the mess that my iPhone makes of JPEGs when you edit them with the iPhone software.

This software processing, upon processing, upon processing, seems an indecipherable jungle to me.

But it still beats processing with silver halide salts.

The fact modern cameras have more data from JPEG files than older cameras had from raw, is down to the larger sensor and Megapixel sizes. The advantage of raw files is it gives a greater dynamic range due to the number of bits the files use. I do not decry images shot in JPEG, but prefer working with raw. I use a camera that only captures JPEG files along with my cameras that capture in raw, so I experience both systems regularly.
For me, most of the thrill in photography comes from post processing. That is why I got into having my own darkroom, back in the day, and it is still the case now. I think of shooting in JPEG as like having the film processed for you, then, once you get the negatives back, going into the darkroom and producing your prints. Working with raw files is like doing your own film developing. Where you choose what "brew" to use and whether to force it or not. For me, working with raw files is not a chore. It is a delight.
And one thing no one can deny. If you blow out the highlights in a JPEG you are sunk, whereas with raw you can usually recover sufficient detail. I know the argument here is not to blow out the highlights but it happens all the time. Digital images have far less dynamic range than film, which in turn has even less than the human eye. Every image has to be a compromise (unless you use multiple exposures and HDR processing) so having the maximum dynamic range to allow you to achieve that compromise can only be a good thing.

Ask yourself, "What's most important for the final image?".

Thank you for that, John.

There are probably some points there that would be debatable, but also there is much that I would agree with and already have. I just think that JPEGs (and those who choose to shoot JPEG) are often unfairly maligned when, due to the way our vision works, normal viewing distances, and the nature of the photos that we view - typically A4-A3 prints or pictures on medium size screens - for the majority of photos it seems virtually impossible to identify whether the final product was processed from a raw file or a JPEG file.

The following is a much less extreme example than the one above:

1. This JPEG of Wrest Park House, being slightly under-exposed, came out of the camera looking a bit dull and flat:

2. So it was edited in PaintShop Pro to make it 'pop' more, and (in my humble opinion!) the A4 print of it looks great:

3: I cannot print at A0 size = nearly 4 feet wide, so as a matter of interest I cropped about one sixteenth of its area, to make an A4 print with the equivalent appearance of A0 for that part of the image. That still looks pretty good to me:

Again, as Ed keeps telling us, and I fully agree, to each his own! Smile


As you say, looks pretty good. And that is viewed on a screen, close to. If it was a 4 foot print you would be at least 8 feet away when viewing it.

Ask yourself, "What's most important for the final image?".

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