Thread: Question on image format and social media

Hi,
Can anyone guide me, which image format is best to post on social media?
Kind Regards

Hi Manoj - I've moved your post to a place where you are most likely to get an answer you are looking for and have changed the title accordingly.

The most commonly used format for social media is a JPEG. Size / quality specs are going to be media specific.

As Manfred says, JPEG is the most common.

For sufficient quality, I recommend 90 pct quality or more. I also recommend maximum chroma or color sub-sampling i.e. smallest-size, often called 2x2 or 4:2:0. Furthermore, it is safest to save the image in the sRGB color space, not Adobe.

For example, 90pct, 4-2-0, sRGB:



There is a slight color cast, image was not color-balanced for this Demo. Artifacts in the middle of the big circle are on the print, i.e. they are not JPEG artifacts.

HTH.

Also check required max image size including file size. Images get auto resized but I prefer to do it myself to prevent any loss of quality. Depending on the actual usage, I normally resize to around 1,000 to 1,400 pixels on the width and about 800 pixels depth and 96 ppi for internet use, but American monitors use 72 ppi. In reality, either one is OK. Then Jpeg #10 (80%). It is something of a balancing act to get close to their requirements.

Use normal Jpeg not Jpeg 2000 which isn't recognised by most internet software.

SRGB colour, as Ted mentioned. Using other colour formats can cause display problems, or with auto conversion to sRGB if using poor quality software.

Originally Posted by Geoff F

and 96 ppi for internet use, but American monitors use 72 ppi. In reality, either one is OK.

Geoff, While I agree with most of your post, the PPI number is irrelevant for any image viewed on screen or posted to a social media site. PPI only has a relevance if you wish to print the image.

I recommend 90 pct quality or more. I also recommend maximum chroma or color sub-sampling i.e. smallest-size, often called 2x2 or 4:2:0.

90%? 90% of what? Adobe software has an arbitrary scale for quality, which is not a percent of anything, AFAIK. It actually seems to have 2 scales: a 13-point scale in PS and a 100-point scale in LR. In fact, the 100 points is bogus, and underneath the hood, it gives you a 13-value scale. For a very interesting discussion of this, complete with sample images, see http://regex.info/blog/lightroom-goodies/jpeg-quality

Re maximum color subsampling: the software I use doesn't offer those options. You get to choose color space, quality, and size (in pixels).

Originally Posted by DanK

I recommend 90 pct quality or more. I also recommend maximum chroma or color sub-sampling i.e. smallest-size, often called 2x2 or 4:2:0.

90%? 90% of what?

90 per cent as in this:



I assumed that the OP has sufficient intelligence to figure out what that means in terms of other people's stupid scales ...

Adobe software has an arbitrary scale for quality, which is not a percent of anything, AFAIK. It actually seems to have 2 scales: a 13-point scale in PS and a 100-point scale in LR. In fact, the 100 points is bogus, and underneath the hood, it gives you a 13-value scale. For a very interesting discussion of this, complete with sample images, see http://regex.info/blog/lightroom-goodies/jpeg-quality

I have little interest in the "Adobe" way, as I may have mentioned occasionally. So telling me what PS and LR do falls upon deaf ears, sorry.

Re maximum color subsampling: the software I use doesn't offer those options. You get to choose color space, quality, and size (in pixels).

That's all? Time to switch, I reckon.

As can be seen, the software I use does offer those options and more - as does any software worth it's salt.

Had a bad day?

Maybe the OP has enough intelligence, but apparently I don’t. The dialogue box says that quality = 90, not 90%. I don’t know what the scale is. Lightroom also has a quality scale that runs from 0 to 100, but those numbers aren’t percents of anything. 0 doesn’t give you a uniform surface.

I’m not an advocate for Adobe software, but it seems a tad odd to label the software that dominates the market and is the staple for many professionals as “not worth it’s salt.”

On a substantive note, I don’t need more options for JPEGs. The ones in Abobe software work fine for posting on the web. (For all I know, they may be the ones you suggest.) With extremely rare exceptions, I don’t use JPEGs for color-critical work, and I rarely keep any JPEGs on my computer.


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Strictly speaking, the quality setting used in jpeg compression relates to the nature of the quantisation table used and the color sub-sampling mode used is a separate setting. However if I remember correctly, I think that Adobe rolls the two settings into one. ie a particular quality setting has a certain level of quantisation accuracy as well as a particular color sub-sampling mode built in to it. eg the top is the highest quality with Color sub-sampling 4:2:2 whereas a lower setting will have lesser quantisation accuracy and maybe 4:2:0.

One way you can find out the color sub-sampling used is to create some jpegs with different settings and look at the EXIF to see what color sub-sampling has been used for each variant.

Dave

Sorry that annoyed you. It was a legitimate question, but in hindsight, there was no reason to repeat “90%”.

Scaling happens to be a professional interest of mine, so that’s what I immediately noticed.

But no, I certainly am not suggesting that Adobe is the only way to go. My point was that many readers here—and probably not only the Adobe users—won’t have all of the options you noted.


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Originally Posted by xpatUSA

In other words, ppi is for printing, not screen viewing.

Technically this is not correct; screens deal with pixels but print media deals with "dots" and print resolution is measured in dots per inch (dpi). And frankly the language in printing is also not particularly clear; my printer uses 8 small dots of colour (8 different inks) to make a "dot". My Epson printer has a native resolution of 360 dpi.

The reason most of us don't worry about dpi is that our display software takes care of those little issues of scaling the image to size, but that involves interpolation. When I do certain operations, specifically some types of sharpening, I want to view my image interpolation, I will set my image resolution to 109 ppi to match the native resolution of my screen (I use a QHD 2560 x 1440 screen).

When I prepare an image for print, I will convert it so that on screen I am working with a 1 pixel = 1 dot resolution. This means I upsample my images to 360 ppi to match my printer's native resolution,

Originally Posted by Manfred M

Technically this is not correct; screens deal with pixels but print media deals with "dots" and print resolution is measured in dots per inch (dpi). And frankly the language in printing is also not particularly clear; my printer uses 8 small dots of colour (8 different inks) to make a "dot". My Epson printer has a native resolution of 360 dpi.

The reason most of us don't worry about dpi is that our display software takes care of those little issues of scaling the image to size, but that involves interpolation. When I do certain operations, specifically some types of sharpening, I want to view my image interpolation, I will set my image resolution to 109 ppi to match the native resolution of my screen (I use a QHD 2560 x 1440 screen).

When I prepare an image for print, I will convert it so that on screen I am working with a 1 pixel = 1 dot resolution. This means I upsample my images to 360 ppi to match my printer's native resolution,

I think we are mixing up 2 things: viewing on your own screen, and viewing posting to be viewed on another. AFAIK, the dpi setting has no effect on the file exported. I just took a file in LR and exported it twice to my desktop, once set at 240 dpi and once at 100 dpi. The files appear to be identical: they are the same size, show the same specs when opened in Irfanview, and open at the same size on screen. It's not obvious what function the DPI setting has in the export module. There is no dpi setting in the Photoshop export or save-as-jpeg dialogs, although the former might allow you to back into it by specifying canvas size.

Originally Posted by dje

Strictly speaking, the quality setting used in jpeg compression relates to the nature of the quantisation table used and the color sub-sampling mode used is a separate setting.

No, strictly speaking quality settings are not part of the JPEG standard at all. What they mean in a particular app is made up by the person who added it to that app. Strictly speaking, the quant tables are not part of the standard, either. JPEG included a sample quant table that has ended up being incorporated in all but specialty applications, although that was not the original intent. In some medical applications, researchers have devised more appropriate application-specific quant tables, as was the original intent of the JPEG group. I myself have devised some mods to the example tables in my pre-retirement incarnation as a medical device software engineer. FWIW

ETA: While speaking strictly, I should mention that JPEG is not a file format at all: it is a stream format. What we think of as a JPEG file is generally a JFIF file, which was a very minimal extension of the JPEG definition to support files.

Originally Posted by DanK

I think we are mixing up 2 things: viewing on your own screen, and viewing posting to be viewed on another. AFAIK, the dpi setting has no effect on the file exported. I just took a file in LR and exported it twice to my desktop, once set at 240 dpi and once at 100 dpi. The files appear to be identical: they are the same size, show the same specs when opened in Irfanview, and open at the same size on screen. It's not obvious what function the DPI setting has in the export module. There is no dpi setting in the Photoshop export or save-as-jpeg dialogs, although the former might allow you to back into it by specifying canvas size.

Actually I am not mixing anything up Dan - I was merely addressing Teds comment on ppi vs dpi. I did not address the posting to the web (as per the initial question). There it makes no difference at all; the only thing that matters there is the number of pixels in the image.

I meant that the thread as a whole mixed two issue. I wanted to clarify for the OP and others that ppi makes no difference for the question originally posted.

Originally Posted by katto

Hi,
Can anyone guide me, which image format is best to post on social media?
Kind Regards

For practical and real world relevance, it wouldn't make much difference to 99.99% of the viewers, who arguably would be viewing the images on un-calibrated monitors, under a variety of inappropriate lighting conditions and for the purposes of addressing the content of the image, not the nuances of quality, tone, colour, etc.

WW