I just checked that leaflet, the flat rate scheme reflects the amount of VAT that YOU pay to Customs and Excise. You would still charge the customer the standard rates of VAT. Normally for photographic services and the items that go with that, prints, canvases etc that would be 20%. This is a scheme for those who only just fall within the VAT requirements, and is simpler to administer as there is much less record keeping needed. You do not get to claim back the VAT on purchases for the business, and simply pay the VAT man a fixed percentage of the turnover 11% in the case of photography. I guess that the rates you pay are based on the average differences between VAT charged on supplies and the VAT you would be paying. If you are mostly supplying services, rather than selling goods then you will tend to be charging a lot more VAT then you would be claiming back. You will notice that Retailing food, confectionary, tobacco, newspapers or children's clothing only pays 4%, this is because much of this retail sector is based on zero rated goods. You can still claim back the VAT on your camera equipment, as long as you spend at least £2000 at a time.
I would think that if you had a photographic services business that turned over between £79000 and £150000 this would be a good way of dealing with the VAT. I know that £79000 sounds like a lot of money but remember that this is based on turnover not profit. If you are doing the photography full time and actually making a decent living out of it then it will be quite easy to hit the VAT registration limit. At least if you do hit the VAT limit this scheme makes it quite easy in the first year, and for your first year you get a 1% discount too. If you are generally selling your service and associated products to the general public there is no advantage to voluntary VAT registration. If though your main customers are VAT registered too, and you are selling them mainly goods then they will prefer that you are VAT registered so that they can claim the VAT back. If you are only selling them a service it doesn't matter so much as either way there is no VAT affecting the cost to them.
The really nasty thing about VAT is that it is a government tax, that can be very complex at times, that you as a business is forced to collect on their behalf, and you had better get right too; OR ELSE!