Captions not transferring to shared folder in Photos

It is intentional. The caption and titles are stripped for Privacy reasons.

See: Shared Album limits - Apple Support

Shared Albums upload a copy of your data. Downloaded content may not contain the same information as the original.

• • Image formats: HEIF, JPEG, RAW*, PNG, GIF, TIFF
  • Video file types and formats: HEVC, MP4, QuickTime, H.264, MPEG-4 

Shared Albums also support special formats that you capture with your iPhone, like slo-mo, time-lapse, Live Photos, and Memory videos. When shared, photos are reduced to 2048 pixels on the long edge, except panoramic photos, which can be up to 5400 pixels wide. You can share GIFs that are 100MB or smaller. Shared Albums do not support spatial photo or video. 

Videos can be up to fifteen minutes in length and are delivered at up to 720p resolution. 

Due to storage limitations, your Apple TV might display only your most recent photos.

*You can't upload HEIF images, HEVC videos, or RAW photos to Shared Albums on your Windows PC.

If you want to share a message with your shared photos, add a comment, when you share the photo.

How to use Shared Albums in Photos on your iPhone, iPad, and Mac - Apple Support

The Shared albums have been around for some years, before Photo.app has been developed with OSX 10.10.3 and iOS 8. We could use them already in iPhoto and Aperture to share photos. At that time even the dates and locations have been removed, not only the titles and captions. The idea has been that when we share photos, we do not want to give away any further information, like where we have taken the photo and when, plus our personal comments. iPhoto ad no tool to strip this information, so Apple did it automatically. Being able to remove information is for example important, when we share wildlife photos of rare species online, so poachers cannot find the place where we took the photo.

The include options you mention have been introduced with the Photos.app, but apply only to sharing by mail or saving photos to Files or sharing with third-party app.

Apple has recently changed the Shared albums a bit. The date a photo has been taken is no longer removed, and we can now sort the shared albums by the date the photo has been taken. This shows that it helps to send feedback to Apple with feature requests. Feedback - Photos - Apple

It is very disappointing that Apple does not support transferring captions on Shared Albums.

Apple has been very slow to provide improvements, as was the case with not allowing a Shared Catalog for families. They need to focus on making the sharing of photos easier.

So Apple try to avoid including features likely to cause harm. Wow! I wish other companies did the same.

I can't come up with anything which I am sure Apple are not thinking of themselves, but have posted feedback anyway.

I guess the Original Poster (and me and everyone else) must treat Location information and Captions, as being just for our ourselves (and perhaps for messaging), and just Share our "Comments". Not too bad I think, so thank you for helping a nooby understand Apple better :-)

Me too.

Tapping "Share", Gives me the default "options",

INCLUDE>Location=On,

INCLUDE>Captions = On,

FORMAT>Automatic= On,

SEND AS>Automatic=On,

AIRDROP & ICLOUD LINKS ONLY>All Photos Data=Off.

However, tapping "Add to Shared Album", then "Post"

results in the photograph appearing in both local and remote "Shared Albums", without caption or location, or even any invitation to add one :-(

I am using an iPhone 11, running iOS18.2.

I have tried different options with the same affect, and am wondering if I should try iOS18.3 beta. What do people think?

Does this mean that there no point in us trying the Beta, and perhaps then reporting a suggestion or bug?

Your mention of "Privacy" sounds very relevant. I am new to this and don't know what previous iOS versions did. I can't work out whether ...

1) Apple have increased privacy by not including the captions and location in the shared photo, but simply failed to delete the (now useless?) "INCLUDE" options that confused me; or

2) When they added the Comment facility, Apple meant to do something - defaulting the INCLUDE options to "off" - for instance, but failed, killing the captions and location instead.

Thanks for a fantastic fast reply so close to what here in the UK is our Christmas. I don't know if I should try the Beta, but you have inspired me to check some more :-)