Visiting Eryri Snowdonia National Park and climbing to the summit of Snowdon, Wales's highest mountain is definitely worth the effort and if you can time your photography trip for sunrise the views are breathtaking. My own favourite photography trip up to Snowdon so far coincided with an incredible temperature inversion where it literally felt as though I was on top of the world. As the sun broke above the clouds the light on Snowdon and the surrounding peak of Crib Goch was breathtaking. If you only ever visit one mountain top in Wales with your camera, make sure it's Snowdon Yr Wyddfa at sunrise. If you're trying to minimise camera gear, which is probably a good idea for essentially a 2.5hr hike above 3000ft, then a standard zoom lens (24-70 full frame) gives you good flexibility regarding composition. If you don't mind some additional weight then add a longer telephoto lens to your kit.
One of my favourite viewpoints for photos of Snowdon Yr Wyddfa, and certainly one of the most popular with visitors to Snowdonia National Park, is from the twin lakes of Llynnau Mymbyr on the A4086 just next to Capel Curig. Access is extremely easy, requiring little to no effort but despite this the views of Snowdon are just stunning especially if you visit on a calm day when the reflections in the lake are jaw dropping. Regarding photography equipment here, a good range of lenses is useful; wider focal lengths capturing the rocky foreground on edge of the lakes whilst longer lenses give you more intimate photo opprtunites of individual peaks of the distant Snowdon Horseshoe.
Llyn Llydaw is a beautiful lake under the shadow of Wales's highest peak, Yr Wyddfa / Snowdon. Access is relatively easy from the large, but extremely busy, parking area at Pen Y Pass at the top of the Llanberis Pass. For photos of the lake you follow the popular Miners Track walking just over a 1 mile to the shore of Llyn Llydaw. The Snowdonia mountains can't fail to impress here with extensive views of Crib Goch, the towering ridges of Y Lliwedd and Crib Y Ddysgl and of course, Yr Wyddfa / Snowdon itself. For photos, you're best visiting early morning as Snowdon and the surrounding mountains are increasingly in dark shadow as the day lengthens; a sunrise photo trip also is your best chance of a “people free” view as the paths to Snowdona are extremely popular with walkers, tourists and photographers at peak times. Photography wise, It's a good idea to have a range of focal lengths again. Wider photos are needed to capture the full scale of Yr Wyddfa / Snowdon and Crib Goch from the side of Llyn Llydaw whilst telephoto shots give you the chance to photograph the tiny figures making their way across the precarious route on Crib Goch or frame a close-up shot of the old mine buildings just above the Miners Track.
As well as the stunning views from the summit of Snowdon, one of the most popular routes used by walkers making the approach is the Pyg Track which is also a fantastic route from which to take some beautiful photos along the way. On reaching the plateau above the Llanberis Pass, just before the double ladder stiles, take a left over the Horns. This is an infrequently visited view overlooking Snowdon and Llyn Llydaw but has stunning wide views, making for some great photo opportunities. The ladder stiles also provide some interesting foreground for shots of Snowdon Yr Wyddfa and as you continue along the Pyg Track the path twists & turns revealing lots of great views to photograph. The final ascent to reach the Llanberis Path and the train tracks of the Snowdon Mountain Railway reveals a fantastic panorama looking back along your route with the famous Pyg Track zig zags making for some great foreground interest.