Sizing

[BH888]

When using the LR Export Dialog Box, how do you distinguish between a high resolution Jpeg image & a low resolution Jpeg image?

In terms of the values in the LR Export Dialog Box, how would you designate an image intended for general Web use?  -- for general Social Media use?

As I understand it, when an image is to be used for FBk, for instance, it is recommended that the image be exported with 2,048 pixels on the long side; - & dpi is irrelevant. For this particular use, what is the significance of the “quality” value in the LR Export Dialog Box?  What should the “quality” value be in this case?

I’ve been told that “dpi” is irrelevant, except for printing purposes, in which case 300 dpi is standard.  If that’s the case, what is the significance of exporting an image at 72 dpi?  -- which some photographers have advocated.

As you can tell from the random nature of my questions, I am confused.

[JohanElzenga]

If you really use Lightroom, not Lightroom Classic, then you cannot specify these things on export (Save to...). If you use Lightroom Classic, then you can set the size in pixels and the resolution in pixels per inch (so ppi, not dpi) in the Export dialog.

Photographers who advocate using 72 ppi for web export do not know what they are talking about. There is no recommended ppi for web export because ppi is irrelevant on the web.

[BH888]

Yes, ppi; not dpi.  ...and am using LR Classic.  My oversight.

Dpi is a measure of resolution then.  With regard to my first question, when a photographer speaks of delivering a "high resolution" image, what value of ppi is he/she thinking?  What value of ppi for a low resolution image?

What is the importance of designating the "Quality" and "Limiting the file size" when exporting an image?

[JohanElzenga]

BH888@aol.com  wrote

Yes, ppi; not dpi.  ...and am using LR Classic.  My oversight.

Dpi is a measure of resolution then.  With regard to my first question, when a photographer speaks of delivering a "high resolution" image, what value of ppi is he/she thinking?  What value of ppi for a low resolution image?

What is the importance of designating the "Quality" and "Limiting the file size" when exporting an image?

Unfortunately, the word 'resolution' is used for different things. When a photographer is talking about a 'high resolution' image, he normally means an image with a large megapixel count, so not some arbitrary ppi value. Others may indeed mean ppi, but without also telling you the dimensions (either in pixels or in inches) ppi is meaningless. I could send you an image the size of one single pixel with a resolution of 2500 ppi...

For general web use an image of about 1000 pixels (longest side) should be fine, unless there are specific requirements.

[melissapiccone]

The only thing that matters when exporting for web is the pixel dimensions - doesn't matter if your image is 72 or 300 ppi.

[BH888]

Given that ppi is irrelevant when sizing an image for the Web and for Social Media, is there a standard pixel dimension (on long side) to designate an image (on export) for general Web or general Social Media use?

[JP Hess]

If I am preparing an image to share on social media or other web purposes, I will usually export with a long edge of 1200 pixels at the most. That is usually plenty big enough.

[Jao vdL]

BH888@aol.com  wrote

Given that ppi is irrelevant when sizing an image for the Web and for Social Media, is there a standard pixel dimension (on long side) to designate an image (on export) for general Web or general Social Media use?

No,

it completely depends on how large you want the image to be seen. Jim's standard of 1200 pixels is pretty good and typically what I use for social media mostly to limit what people can do with the image from a large print perspective as there is a lot of inappropriate image use on these places. For other web use (i.e. websites and blogs) where you control what gets seen you might need to be larger if people are using high definition screens such as iPads or hiDPI retina screens to view your images. So this all depends on your audience.

[BH888]

Thank you all for your helpful responses to my inquiry.  I am gradually getting the hang of “sizing”, although it may take some time to get my head around the idea of an image of “…one single pixel [having] a resolution of 2500 ppi”.

I think what would really be helpful to me at the moment is to tell me how to export a high & a low resolution image, specifically addressing certain fields in the LR Classic Export Dialog Box.

To Export:

High Resolution JPEG, sRGB image, already cropped to 8x10 ratio:

Quality: ??

Limit File Size: ??

Resize to Fit: ??

W:__ x H:__                Necessary??  - since image is already cropped.

Resolution: 300ppi      Only necessary if image is to be used for printing.  Yes?

A JPEG, sRGB image, already cropped to 8x10 ratio, intended for Web Use (assuming that the person needs an 8x10 ratio for their web page):

Quality:  ??

Limit File Size:  ??

Resize to Fit:  ??

W:__ x H:__                Necessary??  - since image is already cropped.

Resolution:                  Not necessary??  - since image is not for printing.

A JPEG, sRGB image, already cropped to a square ratio, intended for LinkedIn:

Quality:  ??

Limit File Size:  ??

Resize to Fit:  ??

W:__ x  H:__ ??              Necessary??  - since image is already cropped.

Resolution:  ??                Not necessary??  - since image is not for printing.

As you’ve explained, values for “W:__ x H:__” affect the actual size that the image will be reproduced on the web or on social media, whatever those dimensions might be. However, if the values for W & H are in pixels, then what is the specific (mathematical) relationship between pixels stipulated in the Export Dialog Box and the actual size of the image when it is posted on a website, FBk, LinkedIn, or any social media page?

Non-photographers and non-LR/PS people do not seem to have a problem with sizing and posting. Why am I having difficulty grasping this?  I would be grateful, if you would read between the lines of my questions.  There may be something fundamental, a basic concept, that I am overlooking or that I need to understand first, which the younger generation (having grown up in the digital age) finds intuitive. 

First & foremost, however, if you specifically address the fields in the Export Dialog Box for each of the examples above, it will probably contribute the most to my understanding, at least for right now.

Thanks for sticking with me with all these questions.