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Old Thursday 25th October 2018, 08:52   #1
marnixR
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png format

my current camera saves the pictures it takes as jpeg files

my practice at present is to take the pictures at their largest size, and then crop and/or shrink them if I want to publish them on-line - all the while maintaining them in the jpeg format

I just wonder whether it would be beneficial for the quality of the cropped/shrunk images if I first converted the jpeg format to png prior to any cropping/shrinking

any ideas what approach would be preferable ?
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Old Thursday 25th October 2018, 10:06   #2
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PNG is not the best format for continuous tone images, it generates much larger files. It is great for graphics with text or boxes as it preserves the sharp edges, jpg does not. If you want a lossless format then use tiff, but you are not going to add in anything that was lost in the original jpg conversion in camera. The important thing is to do all your post processing then save the output sized image, if you need to stop mid flow then you can save the work in progress as a lossless tiff rather than adding an additional jpg conversion.
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Old Thursday 25th October 2018, 15:23   #3
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thank you - i’ll have a go at trying this tiff format + compare it with my current way of working
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Old Thursday 25th October 2018, 17:54   #4
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something weird happened just a few moments ago

i saved the jpeg image to .tif using PaintShop Pro, and then uploaded it to Imgur, and the resulting uploaded image came out as a png image !

so it would appear that this route ultimately disregards the .tif format - or does using that format for the intermediate stage still make a difference ?

[edit]
i notice that the image in jpeg format takes up 359.99 kB, whereas the same image in png takes up 5.61 MB, thereby confirming your statement that '[png] generates much larger files' - not something i had aimed for
https://i.imgur.com/yi8Wehj.jpg
https://i.imgur.com/rWe4Roz.png
[/edit]
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Old Friday 26th October 2018, 04:42   #5
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If you are using a decent tool, like Lightroom, it is not re-saving the JPEG (and thus re-compressing) all the time, it saves the adjustments separately and only re-compresses the output when you export. I'm not sure what PaintShop Pro does. You do want to avoid chaining a bunch of jpeg saves.

Using tiff as your editing format is not a bad solution, but it will be bigger files. I would always do my own export to jpeg to control the quality and down samping, etc., at my end and upload the jpeg not a tiff. otherwise, the site (like you experienced) will do its own conversion.

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Old Friday 26th October 2018, 07:03   #6
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the version of PaintShop Pro I use is a very old one, it appeared to do the job for my simple needs so never got around to replacing it

the current setting on my camera gives me an image size of about 5 MB, which I then resize for upload / publication purposes to less than 1 MB

since I do this operation only once I hope to catch a balance between an acceptable image quality and a page that doesn’t load too slowly

I suppose that under these circumstances there’s little I can do to improve the situation
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Old Friday 26th October 2018, 17:28   #7
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Quote:
Originally Posted by marnixR View Post
the version of PaintShop Pro I use is a very old one, it appeared to do the job for my simple needs so never got around to replacing it

the current setting on my camera gives me an image size of about 5 MB, which I then resize for upload / publication purposes to less than 1 MB

since I do this operation only once I hope to catch a balance between an acceptable image quality and a page that doesn’t load too slowly

I suppose that under these circumstances there’s little I can do to improve the situation
In lightroom, where I can export a file different ways without changing the master, I have a 5 MP (mega-pixel) export for higher quality exports and a small one with a 1136 px long edge, both at 80% jpeg quality. I use the 1136 px to attach to posts here, for example, or email. The 5MP export is 2740 × 1824. For most displays (say 120 - 200 ppi) those would be in the ball park of 1136px @ 144px/in = 7.8" and 2740 px @ 144px/in = 19" long edge. On a Retina display, you need to 1/2 those numbers. The long edge size should be scaled to however you expect to display the image on a screen to make sure the image does not need to get extrapolated because its too small.

The 5MP one save a 34.5 Mbyte (45 MP) Z7 FX shot at about 1.5 - 1.8 MB. The 1136 px saves the same file down to 477 KB. That said, a lot of modern platforms (like wordpress) will take in a large file and then generate thumbnails automatically for the various display sizes. So, on my website I only upload 5MP images and let Wordpress gallery (FooGallery & FooMediaFolders) generate the appropriate thumbnails for quick page display.

What you might consider doing is editing the master without downsampling it and then you can probably "save as" to a second file and downsample that one so you have the original master, if that's something you want.

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Old Friday 26th October 2018, 18:41   #8
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oh, but I think I already do something like that
whenever i’ve uploaded pictures to my computer, I make a copy of the images I will want to use, and then I crop / resize as required - meaning that if I make a mistake I still have the original available
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