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Variable JPEG Compression / Auto Compression

There are now some digital cameras on the market that will automatically select the level of JPEG compression for an image based on image content, file size or other algorithms. This page explores some of these new developments.

  • An overview of JPEG compression and how it is influenced by Image Quality settings in your camera.
  • A recent trend in JPEG imaging in a number of Point & Shoot digicams, along with a few DSLRs, that use variable JPEG compression / quantization tables. In some cameras (e.g. Nikon D200), this feature has been called file-size priority or quality priority.

RAW vs JPEG Basics

When a digital camera takes a shot, it needs to convert the raw image data from the sensor into a standardized file format for storage on a memory card. Typically this is comprised of one of two formats: RAW or JPEG.

While RAW photos offer the highest possible image quality (because the compression is lossless), it has the disadvantage of much greater requirements in file size. The JPEG file format (more accurately called JFIF, which employs the use of JPEG compression internally) offers a very good tradeoff between file size and image quality. A reduction in file size means not only less storage required for your photos on your computer (or archival media), but also faster frame rates and more shots that can be taken in your digital camera's fastest burst sequence.

In most cases, digital photographers choose to shoot in JPEG rather than RAW, for a variety of reasons, but this always means some loss of image quality in the process. Understanding what part of the image quality suffers is complex, but an important consideration for those who want to understand the tradeoff more clearly.

Image Quality / Compression Background

For the purposes of this page's discussion, it is strongly recommended that the reader have a basic understanding of the principles behind JPEG compression. In particular, an understanding of how quantization tables affect image quality would be advised.

Digital Camera Settings for Image Quality

Nearly all digital cameras on the market provide the user with a menu option that is generally labeled Image Quality or Compression. This option often has several different possible settings, typically named: Normal, Standard, Fine, Extra Fine, Super Fine, etc.

What do these settings really mean?

In most cases, these settings are simply an arbitrary name given to an internal scale factor number. This scale factor or Q-factor value is used to scale some internal reference quantization table that is hard-coded in the digital camera. By enabling the user to change the scale factor, different levels of JPEG compression can be achieved (thereby allowing the user to decide a suitable tradeoff between file size and image quality).

To avoid confusing the average non-technical photographer, a selection of two or three quality names (e.g. normal vs fine) is provided to the user as menu options, rather than the setting of the Q-factor itself. 99% of users would have no idea what the real difference between a Q-factor of 80 and 85 really means.

Digital Camera selection of Quantization Tables

In nearly all digital cameras today, the selection of the quantization table to use for JPEG compression is done by the user, and is left constant for all digital photos until the user changes the image quality setting. Thus, for every photo taken in this period of time, the same scaled quantization table will be used.

Why is this a problem?

Image content affects compression ratio

The compression ratio is simply the original raw image data size divided by the compressed JPEG data size (without any of the file headers, etc.). The compression ratio for JPEG images varies wildly, even for the same quantization table or Q-factor.

One of the problems with JPEG compression is that one can't predict the resulting file size after compression, given the Q-factor or quality setting. The final compressed file size is heavily dependent on the image content itself. Factors that increase file size (reduce compression ratio): fine detail in the image, noise and/or high ISO setting.

Advantages with fixed compression ratios

If the compression ratio can somehow be guaranteed (irrespective of image content), then the resulting file size can also be guaranteed. There are some situations where optimizing for a particular file size may be an advantage.

  • Constant bit-rate for video encoding
  • Guaranteed file size per photo of a given resolution
  • Guaranteed number of photos per memory card
  • Guarantee of max image frame rate, writing to memory card
  • Guarantee of number of photos captured at max image frame rate during frame burst
  • Reducing wasted file space due to high ISO noise
  • Frame count remaining predication will hold true, even with ISO changes

Digital Cameras with Variable Quantization / Auto JPEG Compression

So far, I have come across the following cameras that exhibit this feature. Note that others may exist, so if you spot one, please let me know.

  • Sony DSC-H9 / H7 / H5 / H1, etc.
  • Olympus E / C / u / SP / X series
  • Panasonic DMC series
  • Pentax Optio
  • Nikon Coolpix / E (point & shoot)
  • Nikon D series (SLR)
  • Kodak P series
  • Fuji FinePix
  • Konica Minolta DiMAGE
  • Leica Digilux
  • Ricoh GR Digital
  • Casio QV / EX series
  • Cell phones, including: Samsung

Sony DSC-H9 Image Quality (also H7 / H5 / H1)

Disclaimer: I do not own a Sony H-seies, but online full-resolution samples provide a wealth of information that allows some conclusions to be drawn or hypothesized. Web forums have discussed the possibility of image quality issues with the Sony DSC-H9 camera (e.g. noise reduction smearing, etc.), but this page will be limited to discuss the objective compression characteristics only.

Summary of Findings

  • The Sony DSC H1 / H5 / H7 / H9 line of digital cameras all use variable quantization tables for their JPEG Compression. This is not a common feature amongst digital cameras.
  • Variable JPEG compression provides a number of potential benefits, many stemming from the possibility for some degree of control over the final output file size.
  • The selection of the JPEG compression level is determined automatically by the camera (without user intervention), and is calculated by some internal algorithm (likely intended to meet a target JPEG file size)
  • The algorithm used to select this compression level is ultimately responsible for the degree of JPEG artifacts that may be present in the final image.

Comparison of DSC-H9 to other H-Series

It appears that the selection process for compression quality level in the Sony DSC-H9 may be weighted differently than for the other H series cameras. This may be resulting in smaller average file sizes and more compression than from its predecessors. See below for a quantitative comparison.

Compression Levels in Sony DSC-H series

After analyzing a wide range of photos from the Sony H series, I have observed a much wider selection of Q-factors (which influence compression coefficients) than I would have expected. What this means is that the amount of compression used by this camera can vary greatly from photo to photo.

The quantization tables that I see used by the camera are not custom tables as found in most other cameras. Most digital cameras have hard-coded two or three tables that are based on the manufacturer's special definition of the most appropriate quantization table. Sometimes this is based on the JPEG Annex K suggested tables, but most often (e.g. with Canon, Nikon, etc.) these are custom tables.

Even software tools such as Photoshop CS provide a custom table for each quality setting from 1-12.

In the case of the Sony H series, the tables are instead based on the JPEG Standard proposed tables, but with an integer prescale value used to reduce the quantization coefficients as per the IJG quality scale routine. By creating the quantization tables with the IJG quality factor scaled version of the standard tables, it is possible to produce any arbitrary JPEG quality setting without having to store countless tables in the camera firmware. This method won't lead to the most optimum quantization tables, but it does simplify the process greatly.

Q Q LumQ Chr
76 75.8475.76
81 81.09 80.86
90 90.06 89.93
92 91.86 91.90
93 92.96 92.91
94 94.02 93.93
95 95.04 94.91
96 96.06 96.02
97 96.95 96.99
98 97.68 97.93
Integer Quality Settings

 

Note that the range in quality values (of which the above table is only a subset) is very wide, and hence it is conceivable that the camera is able to select from a very wide range in JPEG "quality" values.

My preliminary assumption is that this camera is attempting to optimize the JPEG compression to achieve a certain desired file size per photo (of a specific resolution).

High Quality versus Low Quality

With the potential to select from a range of quality values from (for example) 75 to 98, a very large range in compressed file sizes is possible for the same image content.

Selecting a quality value at the low end of the range (e.g. 75) will introduce a significant amount of JPEG compression with the accompanying loss in detail, the addition of blocking artifacts and other issues. The benefit is the reduction in file size.

On the other hand, selecting a very high quality value (e.g. 98) will allow nearly all of the original image's detail to be preserved and the resulting compressed image will be virtually indistinguishable from the original. The cost of this is clearly an increase in file size (because of lowered compression).

Not all Images are Alike

Competing with the above basic view is the fact that not all image content is alike! A photo that depicts a clear blue sky with very little else is much easier to compress than a closeup image of pebbles and sand, taken at a high ISO. There is more information content in the first example than in the second example.

Compressed with the same JPEG quality, the sky photo will have a much smaller file size than the sand photo.

Original Image Detail Compression Quality   ... Resulting File Size
Low Low   Small
Low High   Medium
High Low   Medium
High High   Large

 

If a camera attempts to use variable JPEG compression to keep the output file sizes constant, what happens?

A difficult tradeoff

Original Image Detail Target File Size   ... Resulting Compression Quality
Low Medium   High
Medium Medium   Medium
High Medium   Low

 

Because we are now attempting to restrict (keep constant) the file size, we have to select a lower image quality (higher compression) on images that have a lot of image detail to begin with. Conversely, we can select a higher image quality (lower compression) for images that don't have a lot of image detail.

Therefore, we'd expect the simple sky photo to have a high JPEG Quality value and good detail reproduction where it may exist in the original. However, in the photo of the pebbles, we would probably see a loss in detail throughout the image.

Restricting compression to meet a given output file size is not good for photos that contain a lot of detail. This feature works well for mediums where data rates have a fixed maximum bandwidth (such as video tape recording and DVDs), as we can overlook the loss in detail for fast moving scenes. But we are a lot more critical of still photos, especially when the image should contain a lot of detail!

The key to how well this works is the decision about what JPEG Quality setting to use for a particular photo.

Possible Implementations of Variable JPEG Compression

Obviously there are many ways that variable JPEG compression can be implemented, and it is especially difficult to guess how a camera may be approaching the issue. That said, there are some indications about what may be happening.

The following discussion assumes that the camera is attempting to create JPEG files with the same file size.

Theoretically, it should be possible for a digital camera to select the optimum JPEG quality value that results in an image that is very close to the target file size. Several attempts at compressing the same image with different quality levels will eventually turn up a quality factor (and hence quantization table) that results in a compressed file size close to the desired size. Remember that it is not possible to predict how compressible a photo is (with normal JPEG) until one goes through the steps of doing the compression.

Towards each end of the available compression quality scale limited by the camera, we would expect that there would be no further bounding of file size. In other words, if an image were completely blank (white sheet of paper), we would probably see the highest quality rating used and a file size that is still less than the target size. Conversely, with a very noisy photo of something with significant detail, we might see the lowest quality rating used and a file size that still exceeds the target size.

Educated Guesses about Image Compressibility

Performing JPEG compression is very computation-intensive, so it is not feasible to go through countless compression attempts with various compression levels before finding the optimum one. So, the camera will make some educated guesses about the values to try The Microsoft patent described later is an example of a clever approach to this mechanism.

Instead, it is likely that this educated guess may be slightly wrong, resulting in a non-optimum quantization table selection which then leads to a compressed file size that is not really near the target file size.

So, if the camera is trying to target a resulting JPEG file size of 2.5MB, you may end up (for example) with actual file sizes anywhere from 1.5MB to 3.0MB.

File Size Targets for Sony H Series?

Working with the assumption that the Sony H9 series digital camera is using the variable JPEG compression to optimize for a particular file size, we can make some rough estimates about what these goals may be. Even though the cameras will produce compressed file sizes that deviate from the target amount, the error in the "educated guess" part described earlier can easily explain most of these differences.

As I only currently have about 40 photos per camera to work with, I have chosen not to post my comparison of average compression findings between the Sony DSC-H5 and Sony DSC-H9 cameras. These sample sets are not large enough to draw an accurate conclusion.

Sony DSC-H9 / H7 vs Sony DSC-H5

With the above caveats and disclaimer, my limited subset of photos seem to imply that the Sony DSC-H9 may be using a lower file size target (and hence higher average compression ratio) than the Sony DSC-H5, even though the resolution is higher (3264x2448 vs 3072x2304). As an aside, my subset of H9 images has a compression ratio of ~10.5:1. What's more: my Sony H9 photo set contains an abundance of high ISO images, which should have only increased the set's average file size.

NOTE: If you have encountered images that exhibit Approx Quality Factor % (as reported by JPEGsnoop) outside of the values listed in the table below, please let me know! Also, for anyone else with an H5 or H9, I would be interested in hearing your anecdotal average file size of collection (and number of photos).

Camera Quality @ Norm Quality @ Fine
Sony DSC-H1 93-98
Sony DSC-H5 93 95-98
Sony DSC-H9 Nightshot: 76-95 Normal:90-98

 

[FYI, the image that produced the lowest quality setting from the H9 was a Nightshot. Limited to non-Nightshot photos, I have still observed quality factors as low as 90 for High ISO photos. Other users have noted non-nightshot photos reporting quality levels in the mid 80's]

As for compression ratios, my sample set shows a definite bias towards higher compression in the H9 versus all other Sony DSC-H series cameras. NOTE: In the following, I have tossed out some of the extreme outliers, and tried to give an approximation of the median ranges.

CameraCompression Ratio
Sony DSC-H16.3:1 to 8.5:1
Sony DSC-H26.1:1 to 7.8:1
Sony DSC-H56.4:1 to 8.4:1
Sony DSC-H98.5:1 to 12.4:1

File Size Histogram

The following histogram shows the distribution of file sizes from a Sony DSC-H7 digital camera, which presumably uses the same tuned level of variable quantization / auto compression as the DSC-H9. This data has been compiled from a reader's collection of over 1200 photos, which should provide a rough view of the expected file sizes from the camera.

From the above data set, the median file size was approximately 2.7 MB for 8 megapixel photos. While this sort of metric is not suitable to analyze for most cameras (as it is extremely variable on the basis of image content), it does have some applicability when considering cameras that may implement file-size based compression goals.

H9 Missing Fine / Standard Setting

The table above shows the range in compression quality values that I have observed in images so far from the different models. It is certainly possible that the previous models in the H-series may use lower compression quality settings for some image types, but I have not encountered them so far. Nonetheless, the trend seems to imply that the H9 might be using more compression than previous models.

As the Sony H9 does not appear to provide a user-selectable setting that allows low quality vs high quality tradeoffs to be chosen, the user is heavily dependent upon the camera's internal choice of quantization tables. Unfortunately, the trend for the non-configurable range of the H9 appears to be one that is not only wider but with a lower average image quality (higher compression). In other words, we are comparing a much tighter range in JPEG quality from the H5 (if we leave it in Fine mode) versus the automatic range selected by the H9.

How Noticeable are these differences?

The most important thing to understand is that most casual viewers will not be able to recognize the nuances associated with JPEG compression (artifacts, blocking, etc.) when high (95+) quality settings are used. Looking at an image on its own, one would be hard-pressed to find any noticeable drop in image quality with these very low compression amounts.

For reference, one can compare image qualities from different cameras to give you a more objective reference. Most recent digital cameras (point & shoot) use an equivalent JPEG quality factor of 93 or higher when set to their highest quality setting (e.g. fine, super, etc.)

So, to some degree, the concern over the variable JPEG compression's effects on the Sony H9 could be overblown somewhat. Even though the camera on average chooses a lower compression quality (with resulting smaller file sizes), it may be difficult to recognize in most prints. Some artifacts may be visible in 100% crops (known as pixel-peeping). It is possible that the camera manufacturer decided to make a tradeoff between burst buffer performance (e.g. 100 shots at high shot rate) versus image quality.

However, more of the concern is probably sourced from the instances of certain images that contain a lot of detail (which don't compress well). It is in these photos that the camera appears to select low compression qualities (e.g. 84-90), resulting in some potentially noticeable loss of detail and introduction of visible JPEG artifacts. This may be further exacerbated by any initial noise reduction algorithm that could be enabled in the camera.

Differences in Compression Quality / Objective

If this difference is true, this would be a very surprising result. Unfortunately, it is also a very difficult characteristic to prove, unless one had the ability to shoot multiple camera models under controlled conditions (same image content, etc.). Without that, the only way to increase confidence in such a hypothesis would be to look at the averages from from very large photo collections.

Does this seem likely?

While most camera manufacturers aim to increase image quality across successive models, it would be hard to imagine any reason why there would ever be a decrease. So my immediate reaction is that this is a misleading result and that it is simply due to too small a sample size.

On the other hand, if such a reduction does in fact exist, then the only plausible reason that comes to mind is the published burst photo specifications:

Sony DSC-H9 Camera Specifications

100 shots @ 2.2 frames per second @ 8 megapixels

The above specification has been provided in the H9's press releases. With this continuous shooting performance comes a hardware and processing requirement that is non-trivial. If the shot buffer is storing JPEG images (i.e. following JPEG compression), then there would normally be a variable bandwidth and storage requirement which is dependent upon image content and ISO setting.

Having some means to restrict this bandwidth requirement would facilitate a camera's ability to guarantee a certain shot buffer performance.

Reducing the file size target (or increasing the average compression ratio) would make more photos fit in the JPEG photo burst buffer. If the 100 shots characteristic were a very important marketing feature to meet, the possibility of a change in target / compression ratio might be plausible.

Related Patents

Microsoft holds a patent that is very much related to this technology, with an end-goal being the optimization of compression settings to target a given file size. If Sony is aiming for a similar goal, then they would need to take a different approach.

  • Microsoft - US Patent 6614942:
    TITLE: Constant bitrate algorithm for block based image compression
    DATE: 1999

    INTERPRETATION: Variable quantization scaler selected by computing a sample compression attempt on two image subsets. Based on the resulting image compression of these two attempts, the target quantization table scaler (Q-factor) can be derived by interpolating from the results of the two attempts. The hope is that the interpolated quality factor will achieve the desired compression ratio.

Soon, I will be posting a deeper summary of the above patent as it describes a fairly intuitive method by which one may implement variable JPEG compression.

At this point, I don't see a patent by Sony on this exact technology, but they do have a couple older patents in related compression quantization methodologies. These are posted here for interest purposes. I am currently looking into their more recent inventions.

  • Sony Corporation - Europe Software Patent EP692881:
    TITLE: Quantization apparatus, quantization method, high efficiency encoder, high efficiency encoding method, decoder, high efficiency encoder and recording media
    DATE: 1996
  • Sony Corporation - US Patent 5374958:
    TITLE: Image compression based on pattern fineness and edge presence
    DATE: 1993

 


Reader's Comments:

Please leave your comments or suggestions below!
2013-04-11cc
 SamSung PL120 also uses Auto JPEG Compression.
And , photoshop too. In photoshop, when Q-factor is from 3 to 12 , for different size picture, it uses two different tables for compression for each Q-factor, but when Q-factor is between 0 and 2 with step 1, it uses the same tables for compression for each Q-factor.
In your blog about "Digital Cameras with Variable Quantization / Auto JPEG Compression", you do not mention them
2009-07-17Masood
 Hi everybody,
I've recently bought a DSC-W270 sony camera. The images I have token by my camera are surprisingly with low quality. It is really ridiculous that such a camera with 12.1 MPixel resolution have no option to adjust output jpeg image's quality manually. Therefore, I contacted the Sony Support Center and requested to provide firmware updates for their products with such a fault. Dear friends, would you please contact the Sony Support Center (support@info.sel.sony.com) too and express your complains. This might be a logical way to convince Sony Co. about our concern.
Thanks
2008-11-27Ronald
 You are Great!!! thanks for all the valuable information you have posted.
2007-12-13Calle
 Naturally, I've been using both tripod and remote to keep the image content as steady as possible. Unfortunately the sun sets around noon here in Sweden this time of year, so I've only got indoor samples to present, and I'm still looking for a really demanding scene and/or camera setting that will truly present comparable artifacts.

However, the bytes/pixel ratio scenario I presented below remains the same throughout roughly 10 different sets. The 8.1MP ratio has been ranging from 0.24-0.31, the 5MP has been 0.32-0.36, and the range of 3MP has been virtually identical to that of 5MP.

An early conclusion could be that the compression of the 8.1MP appears to always be heavier than that of 5MP, unless taking pictures of basically a white wall.

Gladly accepting points and hints!
 That's great information, Calle! Most of the samples I've seen were taken at the highest resolution modes, so I wasn't able to identify that such a trend may exist. Thanks for sharing this. It certainly does hint that slightly better image quality may be achieved in the 5MP mode, but you'd also have to consider how the interpolation / smoothing is being done too (to produce 5MP). On images with highly-detailed content, the higher compression ratio of the 8MP photos may become visible when observed at 100% -- but of course the noise reduction logic may also come into play there as well. Thanks Calle.
2007-12-12Calle
 I made a quick test with my new H7 and compared results from different resolutions, and got some interesting results.

Using 8.1MP, the bytes/pixels ratio of the sample image was 2 215 784 bytes divided by 7990272 actual pixels, that is a ratio of 0.277. Going to 5MP, the ratio was increased to 0.366, meaning a third less heavy compression! Further decreasing resolution to 3MP and 2MP (16:9) resulted in the same bytes/pixel ratio of ~0.366 bytes/pixel.

Thus, from the quick test I performed, one should get the best image quality at 5MP - not 8.1MP.

I hope this is of any value.
 Interesting results, Calle, thanks! Across a range of images, do you see a similar trend? One would have expected a change in resolution (from 8MP to 5MP) would have been accompanied by a similar decrease in file size (by keeping the compression rate somewhat constant), but this doesn't appear to be the case. If you are able to collect a few more datapoints from different images at different resolution settings (on a tripod so that the image content doesn't change), then I would be very interested to see the results.
 
2007-11-09Stephen
 I have to say I am disappointed with the H9. I have been evaluating one for about a week and kept wondering why the images were so poor - especially around edges. I have an older DSC 4MP that takes much better images. There is a lot I like about this camera, but at the end of the day if the images are crap nothing else matters.
2007-06-29mojster
 H9 jpg compression is just too high. Why would we have 8.1 MP camera and ruin picture with compression... that is nonsence..

So.. we alll should write to SONY and demand for new firmware with selectable compression and/or RAW support.
2007-06-02martinezx
 thanks for your review
see my H9 photo tests
on martinezx.blogspot.com
if you want something to test in full size just say
 Thanks... one interesting point of comparison would be to take test photos at different resolution modes (e.g. 3 megapixel, 5 megapixel and 8 megapixel) with the identical shot (i.e. on a tripod). This would help one understand how Sony adjusts the variable compression rates according with respect to resolution. If you can take a few shots of couple different scenes, on a tripod, manual focus, manual mode (i.e. same exposure, shutter speed, etc.) at each of the 3 resolution modes, and post the full-size originals, this would be extremely helpful.

Depending on the results, it may be possible to get around the problem of high compression rates of the H9 camera by simply using 5 megapixel mode instead of 8 megapixel mode.
2007-06-02David
 How does the DSC-H2 compare or fit in your analysis?
 I don't have enough images to do a full analysis of the Sony DSC-H2, but from the assortment of samples that I've seen, the typical compression ratio was around 6:1-8:1 (which is comparable to most of my results for the Sony DSC-H1, H2 and H5 cameras).

Compare this to the average compression ratio I have seen in my collection of samples for the H9, which averaged between 8:1-13:1!
2007-06-01H9-user
 Does this mean that if one shoots 5mp or 3mp with the H9 there should be much less or no artifacts?

Or does the H9 adjust its expectations downward and do the same thing, aiming for a smaller file size with those pictures (thereby meaning that those seeking elimination of artifacts get nothing out of it)?

Also, what would therefore be the suggested tips for avoiding triggering the harsh compression effects based on the research in this article?
 Unfortunately, I have not yet located an online collection of samples from the H9 taken in the lower-resolution modes (5 or 3 megapixel). So, I can't be certain of how the variable compression approach adjusts for resolution. Either the camera chooses similar compression ratios (thereby giving even smaller file sizes), or an allowance is made for less compression at lowered resolutions. My guess would be that the former method is used by the camera, but I don't have samples to test this against. If this is the case, one would get little benefit in image quality from choosing a lower resolution mode.

As for how to reduce the impact of high compression on the image quality, the only realistic solution is to use low ISO modes. Of course most of the time people will choose to use the lowest ISO mode possible given the lighting conditions, so this may not be a very usable suggestion. If the image content is somewhat simpler (large regions of low detail with smaller regions with high detail), then a low compression ratio may be selected, allowing for greater image quality. Again, restricting image content is not practical!

By far the best solution would be if Sony released a firmware patch that allowed the user to control certain critical aspects of the image generation, including standard compression tables (e.g. fine) as well as the ability to turn off noise reduction (which would help avoid the smearing that many users have described).
2007-05-10Laura
 My photographic goal is bird photos for Power Point Presentations projected to audiences of 100-300. I have the Sony DSC H1 use the highest quality setting in JPEG format . I was considering getting the H9 because of the 15x optical zoom. How much image quality am I losing from the camera to my laptop to Picassa photo manager and finally into Power Point 2007? I'd like to make my photos available to nature centers also. Am I losing quality each time I save it on a disk to share?
 Hi Laura -- The only times that you are going to lose some image quality is when a program is resaving (recreating) the JPEG image. The process of transfering the photos from the camera to the laptop and then into Picasa should not involve any actual modifications or conversions on the photos (it should only be copying), hence no loss in quality.

The act of importing the photo into PowerPoint may or may not reduce the image quality -- it depends on your settings. The program offers an option called Compress Pictures which would save a resized (lower resolution) version that would introduce significant reduction in image detail. If the option is not enabled, the original JPEG file should be stored inside the PPT presentation, and no image degradation occurs due to the import.

That said, the act of using a video projector to display the presentation will generally cause a reduction in quality as the image is resized to match the resolution of the projector (generally 1024x768). If the Compress Pictures settings are configured to resave to match the projector settings, then you will experience this loss in quality. Have a look here for some comments regarding this feature in the 2003 and 2007 versions of the product.
2007-05-07Martin Polanic
 Cal, if you're still looking for more, here are links to additional original H9 samples (some at higher ISOs if it matters) submitted a week or so ago by people at dpreview...

http://haiders.net/h9/esther/
or better yet, pick and choose at will from the parent dir:
http://haiders.net/h9/

Thanks much for looking into this and hopefully arriving at some kind of conclusion. Great informative site btw! Cheers! :)
 Thank you very much Martin -- this collection has been extremely useful. The data is starting to show a trend towards more compression in the later model, but I really need to see if these compression levels also exist in the output from the H5 as well (so far I haven't seen such examples yet).
2007-05-07S. Lane
 Thanks for the explanation. Most of the complaints of the H9 are from those who have used the H5. A welcome addition to your document would be a far more detailed comparison between the H5 and the H9. Fewer or more tables? More or less compression?

Also you mention US Patent 5374958. Searching in Google I find it was issued in 1994. Since patents take seveal years, the technology was probably perfected in 1992 or even earlier. That is 15 years ago. You should mention these dates in your description. Surely the technology of this patent must be terribly obsolete by now. Bringing it up without giving a date infers in the minds of most readers that the H9's problems, compared to the H5, may be due to this "new" technology.

If the technology was any good, Canon and Nikon would have been at a serious disadvantage for the past 10 years in terms of image quality. Not the case. This tells me the technology may never have been used.

Just my thoughts. Keep up the good work, and please be more specific about the differences between the H5 (folks like its images) and the H9 (folks are complaining about its images).
 Thanks for the feedback. I have now added more focus on the comparison between the H5 and H9 models, and a trend is beginning to show. Even though I am currently seeing a rather large difference in average compression levels between the models, I don't want to post the average compression ratios yet as at present I don't have enough test photos to draw a more authoritive conclusion.

As for the patents, you have a very valid point. I have revised the section to hopefully make the distinction a little more clear. At present I don't see any invention from Sony that is directly related, but I am in the midst of searching more recent ones now. As mentioned on the page, I think the Microsoft one is the most interesting and relevant, as it would be a fairly obvious implementation of variable JPEG compression, assuming that the end-goal is constant file size.

I'll continue to update the page as I get more data. Thanks!

 


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