When taken to abstractness, iris flowers look entirely different; it's understandable that they are favourite subject of photographers. For more literal photographs, there are a few images of Iris 'Purple Gem from previous years available on the garden's discussion forums. Alternatively, I also suggest trekking over to read Paghat's excellent written account of Iris 'Purple Gem' with accompanying images.
Photography resource link: For inspiration, Adirondack Light: the photography of Mark Hobson. Navigation is a bit tricky, so here are the three gallery links: Ku SQ Thinking, Krappy Kamera and Ku Triptychs.
Gorgeous!
Oh my gosh!! Those 'Purple Gems' are absolutely breath-taking! I plan to put them up as wallpaper.
Listed elsewhere as a cultivar of Iris reticulata, as at second link (above). If this is accepted here then it should be listed here as I. reticulata 'Purple Gem'.
No, we generally choose to follow the RHS convention for cultivar names of non-North American plants. They use Iris 'Purple Gem', with (Reticulata) in brackets, suggesting that Iris reticulata is somewhere in the parentage, but not necessarily the only species involved.
What's the RHS convention? The RHS Plant Finder? The RHS Nomenclatural Database? The (shudder) RHS Index? An iris checklist produced by the RHS? The first three all have marked inconsistencies or outright gaffes that pop up when checking specific plants. I try to look at monographs when I can.
Generally, the RHS Plant Finder.
.....On the line of Perfections.....
It's perfectionism if you don't know or care enough about it to understand an interest in accurate naming and historical information. The Plant Finder has had plenty of mistakes in the past, I would never use it as the last word myself. Then there is the matter of plants in cultivation over there under the same name as plants in cultivation here but not actually being the same plant.
I interpreted victor's comment to be about the photograph, not about the naming information.
As for the RHS Plant Finder, I suggest taking a second look at it. It's improved by leaps and bounds in recent years, but I don't know what era of the book you are referring to. I had a look at the 1998-99 edition just now and it is indeed not something I'd rely on – at that time, it didn't even give a genus-by-genus supporting bibliography (which it does now).
I just look at the online version these days.
http://www.rhs.org.uk/Databases/HortDatabase.asp?ID=93514
Gives an article in 'The Garden' as a reference for Iris 'Purple Gem'.
Some additional background:
THE EUROPEAN GARDEN FLORA - VOLUME I*
"Hybrids have been produced between I. reticulata and I. bakeriana; they can be identified by their leaves, which have c. 6 ribs....[I. bakeriana is] Very like I. reticulata; in the wild intermediate plants have been found. It is probably best regarded as a variety of I. reticulata as in FLORA IRANICA (1975) where it appears as var. bakeriana (M. Foster) Mathew & Wendelbo."
A framed set of 'Iris Species Watercolors By Jean Witt, Presented By King County Iris Society November 4, 1991' displayed on a wall of the Elizabeth C. Millier Horticultural Library in Seattle includes as subjects I. bakeriana, I. reticulata and I. 'Purple Gem'; the last, while shown next to I. reticulata and superficially similar can be seen upon closer inspection to clearly consist of a combination of characters of the two others.
THE PLANTFINDER'S GUIDE TO EARLY BULBS**:
"I. 'Purple Gem' is an I. bakeriana seedling."
'The Garden' 126(1) page 31***:
"Many of the plants commonly grown today were produced in the 1940s and 1950s by the van Tubergen nursery in the Netherlands. Among their successful cultivars are I. 'Joyce' and I. 'Harmony', which are both hybrids between I. reticulata and I. histrioides, and I. 'Clairette', I. 'Pauline' and I. 'Purple Gem', all selections of I. bakeriana."
*1986 Cambridge University Press
**2000 Rod Leeds
***2001 The Royal Horticultural Society
Given that information, I'd conclude Iris 'Purple Gem'. If Iris bakeriana 'Purple Gem' existed in publication somewhere, I'd also consider that, but I am not so bold as to do so without any support whatsoever.
Yesterday I also found that the RHS 'The Garden' (same article) observed I. reticulata was probably also a garden form. However, B. Mathew (in one of his books, I didn't note which) noted wild collected I. reticulata that were quite like familiar cultivated stock.