What happened to my Railwire images?

[jagged ben]

Reducing a filesize by a factor of 10 suggests only about a 2/3rds reduction in height and width (if the compression quality is not also changed) since area is the square of the linear dimensions.   That's not at all unreasonable for large format photos taken on today's cell phone and cameras, since they would more than fill just about anyone's screen if viewed at full resolution anyway.   But it is indeed a problem for images with small text or diagrammatic detail that gets lost at lower resolution.  The two solutions are: 1) make that text or detail bigger in the original so it's still readable when downsized, or 2) crop the original and save as additional files to show relevant details, upload separately and they won't be downsized so much if at all.

[mark.hinds]

Reducing a filesize by a factor of 10 suggests only about a 2/3rds reduction in height and width (if the compression quality is not also changed) since area is the square of the linear dimensions.   That's not at all unreasonable for large format photos taken on today's cell phone and cameras, since they would more than fill just about anyone's screen if viewed at full resolution anyway.   But it is indeed a problem for images with small text or diagrammatic detail that gets lost at lower resolution.  The two solutions are: 1) make that text or detail bigger in the original so it's still readable when downsized, or 2) crop the original and save as additional files to show relevant details, upload separately and they won't be downsized so much if at all.

As the OP for this thread, I will venture to comment here.  If your "factor of 10" is derived from one of my early comments, I'd like to clarify that I was not in any way referring to file size reduction from my original.  Rather, I was questioning the variation in the final reduced file sizes in my Railwire Gallery, which vary from about 40kB to about 400kB (factor of 10), apparently independently of the file size of my originals, which is a very different thing.  In turn, this made me wonder if there was a way I could control this during the upload process.  The interim consensus is apparently not. 

MH

[peteski]

In turn, this made me wonder if there was a way I could control this during the upload process.  The interim consensus is apparently not. 

MH

I will say it again: If the photos you are uploading are already reduced down to <1280 pixels across, then I believe the file size in the gallery will remain the same as the original photo you are uploading. So this way you would have full control of the file size. I have not actually done any checking, but it seems logical.

[jagged ben]

As the OP for this thread, I will venture to comment here.  If your "factor of 10" is derived from one of my early comments, I'd like to clarify that I was not in any way referring to file size reduction from my original.  Rather, I was questioning the variation in the final reduced file sizes in my Railwire Gallery, which vary from about 40kB to about 400kB (factor of 10), apparently independently of the file size of my originals, which is a very different thing.  In turn, this made me wonder if there was a way I could control this during the upload process.  The interim consensus is apparently not. 

MH

Okay, perhaps I misunderstood.  But I still think it's perfectly natural for compressed images to vary by that much depending on their content.  For example an image that is a diagram consisting of a few black lines on a white background essentially only has to record the location of the black lines; the compression algorithm can essentially describe the background areas to be colored white with the same data points.  Thus it can be compressed much much smaller in bytes than a brightly colored photograph with lots of different colors.  Or put another way, the bright colored photo suffers much more greatly in quality if reduced to the same file size on disk. 

Now, as is being discussed in this other thread, it does seem that the resizing algorithm is doing other things besides just resizing so you're correct that 'there's more to it' than just reducing the size.   The point is that trying to figure out 'what is going on' by looking at file sizes is quixotic, because between the image size (number of pixels), the color variation of the original, and whatever quality shortcuts the algorithm might be taking in resizing, there are too many factors to expect any kind of pattern.

[MK]

What Ben said!

[mark.hinds]

I will say it again: If the photos you are uploading are already reduced down to <1280 pixels across, then I believe the file size in the gallery will remain the same as the original photo you are uploading. So this way you would have full control of the file size. I have not actually done any checking, but it seems logical.

I already tried this, and no it doesn't.   

[peteski]

You're right - I just tried it  myself.  I forgot about watermarking that is done when the photo is saved. That means the JPG gets modified whether it is resized upon upload or remains original size (X-Y dimensions).

I bet that a non-lossy format like PNG would result in no loss of quality, but since the non-lossy compression is used, the files are larger than the equivalent JPG file

[John]

This might be a good time to say this

Don't upload your pictures here with the expectation that they will always be here.  Too many things change in the online world. There may come a day when TRW ceases to exist. Back up your images.

[peteski]

This might be a good time to say this

Don't upload your pictures here with the expectation that they will always be here.  Too many things change in the online world. There may come a day when TRW ceases to exist. Back up your images.

John,
That was never my intention. But we all know how it sucks when there is some useful older thread here, but the photos hosted by a 3rd party site disappear, for whatever reasons. Photos are gone and the useful thread becomes useless!

Hosting photos locally on TRW pretty much insures that the photos will be visible on the forum for as long as the forum is around. That is all I hope for.  I had no inklings of using this forum's gallery for permanent photo storage. Besides, uploading them here also degrades their quality (and sometimes size). This site is free to use, so I only expect as much as I paid for. 

All my images are always backed up, usually on 2 external backup devices (one is offsite).  I work as a tech support engineer dealing with computer storage arrays, so I see first hand the dangers of not backing up data. Surprising how many business fail to do that, resulting in permanent data loss of their important business information.  It is sad and scary to witness.

[tom mann]

I compress these images heavily in addition to resizing.  The resized one is called "medium", and that is the one intended to be added into a post (it's 1024px across).  The large one is there somewhere too, and that is a compressed version that is the same dimensions as your original, just compressed.