I've been reading and thinking about visualization lately. In particular, aphantasia
https://en.wikipedia.org/wiki/Aphantasia
https://www.facebook.com/notes/blake-ross/aphantasia-how-it-feels-to-be-blind-in-your-mind/10156834777480504/

This has led me to wonder: what would happen if a hundred of these hardcore adamant 100% aphantasic people did a 2 week fire kasina retreat? Could they even get the red dot?

I've also noticed that I see an obvious distinction that isn't clearly cut in many places
1) Images occurring in "alternate visual space" -- the space where one recalls a memory. This is where 99% of my visualization takes place. The images aren't imposed over what I'm seeing with eyes open nor imposed over the "black screen" I see when I close my eyes. Visualization that aids problem-solving etc occurs here for me. If I'm trying to remember the definition of the Intermediate Value Theorem I quickly 'see' a little continuous graph on some small interval. I can also manipulate images in this space.
2) Images that appear to be actually projected onto open-eye field or projected onto the "black screen" we see when we close our eyes. Some of the imagery described on the OG Fire Kasina retreat seems to fit here. I consider the red dot to be here too (and the clouds of flowing color). Fullblown 'hallucinations' would be here.

I have some questions pertaining to these two categories:

Do these categories seem reasonable to you?
At what point during the Fire Kasina practice does the imagery in type 2 become more detailed/permanent?
Does the practice also enhance type 1 visualizations? iirc, in the podcast about it, Daniel would say something like "I flashed onto an image of ___". That seems to be a type 1 visualization by my definition.
Are type 2 visualizations common?
Does "concentration practice" as typically understood on this website develop type 1 and type 2 visualization equally?

Using these two categories as vocab I also have some theories about aphantasia.
a) Some people think that almost everyone has constant, easy, type 2 visualization access and so if they don't they think they're aphantasic.
b) Some people are unaware of their type 1 visualizations (but they're occurring nonetheless), so they think they're aphantasic.

I might post some of this to the aphantasia subreddit and see what they think.

I welcome relevant comments. Anyone have aphantasia?

Bump I guess

edit:
Okay, I'm making this bump useful now.

On the aphantasia subreddit I've been looking at various posts about people purporting to 'cure' their aphantasia. Here is a recent one which links to an article seeming to describe a practice similar to the fire kasina,
https://www.reddit.com/r/Aphantasia/comments/92wfqa/another_cured_aphant_2_kinds_of_aphantasia/

Fascinating! I've never heard of this syndrome(?) before.

Excellent questions! I have observed the very same distinction and written about it on my facebook page (in Swedish). I have access to type 1 visualizations, although other senses are stronger for me. When I think about my partners I usually think about their touch and smell, and through that I also have access to visual images, mostly in detail because that’s where I’m able to feel and smell. I find it difficult to visualize my favourite beach in a way that shows a scenery in 3D, but it’s possible because I have the memories to draw from and can also connect to smell and physical sensations. Rememering images from photos is easier. None of these visualizations are projected onto the black screen, and I can’t even imagine placing them there. Thank you! I’m relieved it’s not just me! I have difficulties placing them geographically at all, but I have noticed that I tend to gaze upwards to the right when I focus on doing these visualizations, so maybe that’s where they are. 

When it comes to type 2 visualizations, I can easily imagine geometrical figures and colors being placed in front of the black screen. I don’t really see them, though. Fantasizing about things or persons or places I haven’t actually seen is really difficult, and they are not on the screen. In the kind of guided meditations (hypnoses) where you are supposed to meet a spirit guide or a spirit animal or something like that, I usually can’t visualize anything. If I manage to do it, it’s mainly touch. I can’t imagine a generic beach scenery apart from real beaches that I have seen. I can however imagine the somatic sensations from the sand, the wind, the water, the warmth of the sun... I did draw things from my imagination as a child. I often drew illustrations to books that I read. I could see what I read (not on any screen, though), but not very vividly.

In my lucid dreams, either the visual has felt like watching a movie on a large screen rather than being there, or it has been dark or otherwise unclear imagery. When I try to look closer at thing, they dissolve. Touch feels very solid, though, but not in a way that tells me what the objects are. It’s just texture and density. 

I don’t know if I qualify as having aphantasia. My visual imagination is not very strong. I have seen the red dot, though, just from staring at a candle for a few minutes. I have also seen psychedelic color formations and lights just from hearing certain sounds at low frequencies at an experimental dance show. I really saw them in the room. I thought it was part of the show first and was impressed. Then I realized that there was no way that they could have accomplished that kind of effect, especially when my partner next to me started to shine brightly.

In dreams, when I try to read a text, the words keep changing and make absolutely no sense, because nobody has written it. That’s how I know it’s a dream (combined with the fact that there are no toilets in private anywhere, but that’s another story).

Seeing an after image after staring at something is a physical phenomenon related to mechanisms in the eyes (I can describe it in Swedish but not in English), so of course one is able to see something then. Still, it’s true that I can imagine a candle flame very vividly now after staring at one for 15 minutes about a weak ago, or maybe a couple of weeks ago. Maybe I should do it more regularly to see if anything happens with my visualization skills.

I have found that if I draw a portrait of somebody, it is much easier for me to visualize them afterwards. That is also the case if I have felt the lines of their face with my hands.

Interesting thread ... for me:

Do these categories seem reasonable to you? Yes.
At what point during the Fire Kasina practice does the imagery in type 2 become more detailed/permanent? Immediately. As soon as I turn my attention from candle flame to after-image, this results in a Type 2 image. It's completely distinct from a Type 1 image. 
Does the practice also enhance type 1 visualizations? iirc, in the podcast about it, Daniel would say something like "I flashed onto an image of ___". That seems to be a type 1 visualization by my definition. I have always had a strong capacity for Type 1 visualisations and as far as I can tell, FK practice has not improved this in me. 
Are type 2 visualizations common? I think they occur as you mentioned - during FK practice, under the influence of psychedelics, as a result of organic visual hallucinations. In my case, I have not seen a Type 2 visual in 'everyday' life. FK was actually the first time I experienced a Type 2 visual, which is what made the practice so interesting to me. 
Does "concentration practice" as typically understood on this website develop type 1 and type 2 visualization equally? No idea! 

Today when I relaxed after my yoga practice I decided to try to visualize that candle flame that I can still remember so vividly efter focusing on it for only fifteen minutes a while ago. To my surprise, not only could I do a type 1 visualization of it from my memory, but I could also project it onto my black screen. It was faint and only lasted 1-2 seconds each time, but I saw it. I didn’t just remember seeing it, but it was there right next to the purple swirls that are usually there.

I think I need to take up this practise to see what it does to my visualization skills.

Maybe that’s what the practise is about, among other things? Eliminating the distinction between type 1 and type 2 and thus making images more readily available to us as a tool?

There's tons of info on fire kasina practice (including a glossary of "shop talk") on another site created by Daniel right here: https://firekasina.org/  It's a really fun technique! 

And BTW Shannon Stein, who co-authored the Fire Kasina book with Daniel, has said she had at least some degree of aphantasia going into the practice and that didn't stop her from seeing all kinds of cool stuff. 

I have planned to read that book as well and have started just a little, but I’m focusing on MCTB2 and Shinzen Young right now. Interesting that Shannon Stein had such difficulties. That certainly brings hope.