Comparing JPEG Quality

Use this page to compare the quality of JPEG image compression used in various sources, including both digital SLR / digicams (Canon, Nikon, Sony, etc.) and image editing software (such as Photoshop). Note that this is a comparison on each camera's JPEG output — with RAW output you can bypass the compression quantization "error" step. The data points for Photoshop and IrfanView are useful to determine how the final output quality compares.

This interactive page is very new and will be improved over time. Please leave any feedback or suggestions below. Do you want to see data about a camera that is not listed below? Let me know and I'll add it.

Variable Compression / Quantization

Note that there are a growing number of digicams that use variable quantization tables to produce their JPEG output. As a result, it is possible that a camera may generate photos that use a dozen different quantization tables, meaning that the effective compression quality can, in fact, cover quite a large range. For this reason, I have omitted many of these digital cameras from the list below.

Important note about Quality Factors

It is extremely important that the reader understand that compression quality cannot truly be represented by a single value. JPEG compression quality is actually defined by a pair of quantization tables (each with an array of 64 values). Trying to make a comparison between a pair of matrices is not at all straightforward (or always possible).

So, then why are "quality" numbers listed for each camera/software source? Many programs encode their JPEG images using quantization tables that are generated by scaling the coefficients in a "standard" table that is provided in the ITU-T specification.

The IJG group has proposed a method of scaling these coefficients according to a "quality factor" scale. This is NOT a percentage! It is merely a number from 1-100 representing the scaling factor used in generating the table. A quality factor of 100 does not mean Lossless compression! Instead, it generally represents the quality factor that will generate the highest quality compressed image with the provided scaling algorithm.

That said, many software programs and some digicams are indeed using scaled versions of this standard table. If we know that a given program has used the IJG scaling method, then we can indeed make a comparison, because all numbers in the matrices will move according to the algorithm in a similar manner.

So, what about other digicams / software editors that didn't use the IJG scaling method? People always love to make comparisons, and comparing multiple 64-element matrices is not intuitive to the average person. Therefore, as an incredibly rough approximation, a calculation has been made for each source to derive the closest / approximate IJG quality factor for a given table. If the quantization tables follow the standard trend of limited compression in the low-frequency components rising to moderate compression in the high-frequency components, then the approximate quality factor may indeed give one an idea as to how the overall quality may appear.

How to Compare Matrices

When you use the comparison tool below, an assessment is done between the sets of 64 coefficients that make up a quantization table. In order to come up with a better than / worse than assessment, the tables are simplified into high frequency coefficients and low frequency coefficients. If the high frequency coefficients in table A are nearly always greater than the high frequency components in table B, then we can indeed state that digicam A's high frequency content will be compressed more poorly than digicam B. In cases where there is not enough of a clear difference, the comparison will report this accordingly.

JPEG Comparison List of all Cameras & Sources

The following is a sorted summary of the JPEG Quality factor comparisons between all cameras and other sources including Adobe Photoshop and IrfanView. The list is ordered by the approximate luminance quality factor (please see above!). This is only a very rough comparison as the quality factor is not necessarily a good comparison as it doesn't discern between low and high frequency component differences in the same way that the Human Visual System does. Thus, it is only a starting point -- consult the quantization tables themselves for a more accurate comparison. It also provides a loose guide as to the quality settings in Photoshop Save As when coming from various digicams.

The other very important point is the chroma subsampling being used in the chrominance channel. Note that a camera with a subsampling of 1x1 (i.e. none) and lower chrominance quality factor may appear better than an image compressed with a subsampling factor of 2x1 and a higher chrominance quality factor. Note such a changeover in the Photoshop quality factors, where the subsampling is automatically chosen depending on the quality level.

Lastly, sources with the same quantization tables have been grouped together, as they should all have equivalent JPEG compression quality. Of course the following does not take into account any of the differences in optics quality, CMOS/CCD sensor resolution or quality derived from a RAW->JPEG workflow..

NOTE: The following is not an accurate comparison of quality (as it is just listing the approximate quality factor, which only truly applies if the IJG tables were used). Direct quantization table comparisons (using the drop boxes above) will provide a more accurate comparison. The list below can only be used as a rough ballpark comparison chart in light of the limitations of "approximate quality factor" described earlier.

Related background material

• JPEG Compression
• JPEG Quantization