Before you decide ‘I will never travel to Cape Town in winter’ there are important factors to consider, especially since some things simply cannot be done in summer such as:

Another important aspect of the Cape winter season is that the weather changes rapidly so we seldom have long uninterrupted spells of any kind of weather. Every cold front has its shoulder days which are often calm, clear and absolutely perfect for photography as one can photograph all day.
And even when it rains there are still amazing photographic opportunities to be had. An award winning BBC photograph was taken of a mushroom being pelted by the pouring rain. In the rain you could potentially get poignant images of sodden sad looking baboons, birds shaking the rain off their backs or children huddled under colourful umbrellas etc.

It seems in recent years the pattern of long rainy cape winters has changed, possibly due to the ‘El Nino affect’ so now instead of experiencing back to back cold fronts we have a numerous days inbetween of mild weather and sunshine.
This is the reason that the cape winter is now been called the cape's 'secret season'. If you're prepared to take your chances with the weather, it proves to be an exceptional time to visit especially as a photographer. All the main tourist attractions are tranquil and un-crowded and there is nothing quite as awe-inspiring as photographing the ‘Cape of Storms’ in full swing.
Also the ‘quiet season’ can be a more affordable time to travel with discounted rates on airfares, accommodation, tourism activities, shops and restaurants.

WITH GLOBAL CLIMATE CHANGE OUR WEATHER PATTERNS HAVE BECOME LESS PREDICTABLE MEANING IT CAN RAIN IN SUMMER OR BE SUNNY IN WINTER.