Avenue for high quality photos

Approach it from the perspective of goals.
Is the goal to show off the photo? The visitor will need a big screen and a lot of bandwidth to properly appreciate the high resolution.
Is the goal to sell the photo? You can’t control where the photo goes once it is coded into a web page. The visitor has to download it for the browser to paint it, so if you are selling, don’t show the actual photo anywhere in your pages.
Is the goal efficient use of storage? Human eyes can’t distinguish the difference between 72dpi and a higher resolution, so it’s a waste of bandwidth and disk space to use the higher resolution in a web page. You can FTP the large images to your server and link to them so visitors can download or view them, but if you upload using WP then it will make all the smaller sizes, which uses more disk space.

Not knowing your goals, I suggest you only load the large images via FTP and only if you are supplying it for visitor download. Make a reasonable size (72dpi for the average window size -maybe 1200px) for use on a web page and upload that through WP. WP will make smaller sizes according to your Media Size Settings, and these can be used on your page or in a gallery plugin.

Goal: Show off the photo very well. Photos (professionally taken) are of commercial light tubes that I would like to sell to customers. I would also like efficient use of storage – if size could be reduced while maintaining same observable quality, I would like to do that.

An example of a photo is 300 dpi, 8061 x 5374 pixels, jpg.

Since you haven’t mentioned any plugins, it seems you are recommending I do it all manually? I don’t fully understand what you mean when you say upload images via FTP and then you say make a reasonable size for use on a web page and upload that to WP. That sounds like 2 different paths. One – upload originals via FTP to server, and two – resize (or reduce dpi) manually and upload through WP.

One of the reasons I mentioned using plugins is because I have 38 photos for this project that I would like to include, and manually resizing each one seams like a lot of work.

Thanks for the reply! And, sorry if this is a bad question. I genuinely did look into this and am unsure of how to maximize quality while minimizing disk usage.

Since you haven’t mentioned any plugins, it seems you are recommending I do it all manually?

Well, I needed to know the goals first.

Photos (professionally taken) are of commercial light tubes that I would like to sell to customers.

The way this is worded, I can’t tell if you are selling the light tubes or the photos.

That sounds like 2 different paths.

Yes, that was my point. If the photo is the product, you want to make it so the visitor can’t get it unless it’s paid for. And if you aren’t selling it, you need to give the visitor a choice of downloading, because that’s a lot of bandwidth to waste (for both of you).
The “big image threshold” was added to WP in version 5.3, in which WP treats any image over the threshold (default of 2560px) differently, and makes scaled down versions for use on your pages. You can set the threshold programmatically.

Manually resizing is not that hard. I use a program like Irfanview or Xnview which has a batch mode, and you can tell it to make the longest side whatever size you want and also set the dpi to lower. There truly is no reason to use a large dpi for most things. If you use a plugin that has a zoom feature, like is on most ecommerce sites, then the higher resolution is handy, but you don’t load that image until the photo is zoomed (so it’s a choice). There are online services to Smush your photos also.

I’m not going to recommend any plugins, because I haven’t used any, and I’m still guessing at what you really want. Think of how big most people’s screens are, and shoot for that. My laptop has a 1920px screen. To zoom in to twice, that would be 3840. That’s probably way more than you need. Most hosting has quotas on bandwidth, so be careful or you’ll use it all up with not much traffic, for not much benefit over a smaller image.

I am an affiliate for the lights. The actual physical lights are the product.

I got Irfanview and what I did was ctrl + r, kept the same size and dpi, but resampled with lanczos to drastically reduce the size on disk. The results are better than anything I’ve ever seen before. The size range is now 450kb to 1250kb with same noticeable quality! (from 5-8MB before).

So I have all my pics now, and will upload them via FTP soon, then I think I’ll just use WP in built re-sizing. Since Irfanview already compressed it, I don’t think there is any use in a plugin unless it gives me other benefits.

I will update later. Thanks for the help!!!

I have finished the webpage (tomitechnologies dot com) but gtmetrix gives it an F.

I think the size of the photos may be the biggest reason why.

I am happy with the image sizes, but I think it’s loading all of the photos in their original, on the main page. I want it to load the original in the same way this page does (https://om4.com.au/client/preparing-image-files-before-uploading-with-wordpress/) or alternately, manually clicking it ‘open image in new tab’ is fine. But I want it to only load smaller photos on the front. I have my ‘large’ set to 1024pixels and I am happy with that on visual (the page I linked), but WP did not create this. So, is this the point where I should activate ShortPixel?

p.s. I didn’t write out the link to my site because I don’t want bots locking on and forever trying to hack it.

No, ShortPixel is for compressing images.
Your problem is that the theme or plugin that you are using to output the images is using the original uploaded size. WP is adding the srcset attribute, so it is doing its part correctly. You need to look for an option for choosing which image to use, or ask at the support forum for the theme or plugin doing it.
A normal image added to the editor would give an option for which image size to use. But you are using some sort of slider, which is not part of WordPress.