The Water of Leith walkway runs right across the City. It passes the Gallery of Modern Art. There's a gateway and steps dropping to the waterside.
The pathway wends through many Edinburgh Communities and sorry, Mary, I disagree: there's plenty to keep a photographer occupied, with waterslides and weirs, the Marvellous and venerable Dean Village, The Georgian St Bernards Well near Stockbridge. I'm not so much thinking tourist panoramas as interesting compositions.
You also pass very close to the Royal Botanic Gardens, with fascinating glasshouses, herbaceous borders, a big collection of trees. It also has Inverleith House, which hosts exhibitions, usually retrospectives of contemporary artists. Sometimes photography.
Returning to the WOL and passing on north-eastwards, you pass into an older industrial landscape - nonetheless lots to photo. Sometimes following the river, sometimes abandon rail lines.
As you emerge into the Basin of the water of Leith you will arrive firstly on Coburg Street, with a workshop of about 50 artists and artisans, the Coburg Gallery, and also the Water of Leith Cafe Bistro, often top rated on TA's restaurant list.
Then you arrive on the shore - with the Leith Gallery/Waterside Arts and also the smaller but just as interesting shop belonging to Ritchie Collins ... hundreds of people stop outside Cafe Trufa to take photos of the view down the Shore and into the Docks. Fantastic view. A mix of old leith and modern architecture, but sympathetically developed. Less known is Lambs House, a 16c property renovated by a local Architect, tucked behind some buildings on the shore.
The walk from the gallery to Leith Docks would take maybe 90 minutes, but if you're busy snapping, potentially longer.
I absolutely understand why people are telling you about Queensferry. It too has a collection of crow-stepped gable buildings, and has of course a couple of bridges, and some islands ...
On that basis you might go to Cramond, just on the NW boundary of the City: a small river and some interesting buildings and seascapes.
I've seen more photography in the Smaller Modern Art Gallery than in the larger one which tends to concentrate on contemporary art ...
There are also two smaller galleries in Market Street, just behind the station. Both have had photographic exhibitions in recent memory. The city art centre, the Fruitmarket Gallery. There's also the Stills Gallery (unsurprisingly photographic) on Cockburn street, no distance away. The National Galleries operate an hourly Shuttle from the Mound to the Modern Art, but it may be less hassle to hail a taxi.
Water, but stationary: there are two decent size ponds with bird life; and there are the slopes and crags of Arthurs Seat. Lot of rock architecture, panoramas of the city.
You don't say when you're coming so difficult to be specific about what's on. But if you research the places mentioned I'm sure their websites will contain details forwards right through the Summer.
I appreciate there are too many places to visit in just 24 hours, just trying to flesh out your choices within the city.
I think you could string together a number of city centre galleries, hop to the Modern Art Galleries, then head down the water of Leith - a lot of the places I've described could fit together on a single busy itinerary.