When setting the aperture at f1.8 you are for sure going to overexpose the image. When I'm out at the beach I set my GH5 at f1.8 with the shutter speed 1/8000 and my iso at 200, but I still get an overexposed image. What can I do?
The easiest way to solve this problem is to use a neutral-density filter. They are essentially neutral grey filters that cut down on the light reaching the film or digital sensor. Good ones are fairly expensive, because they are surprisingly hard to manufacture.
Another option is to shoot in more favourable conditions, like overcast days or really early or late in the day, when light is less bright.
In a pinch, a polarizing filter (which is something most photographers carry with them most places they go) will cut down light by about two and a half stops, or a factor of about five, which can be the difference between overexposure and correct exposure in some situations.
Turn your ISO right down to the minimum value
Do you really need f/1.8? Depending on the composition of your shot you can usually still get decent shallow DoF up to around f/4.0
As people have already mentioned, use an ND filter. You can get variable ND filters fairly cheap online but be wary if you're using them at high settings or long exposures they tend to cause vignetting and other side effects. If you can, buy trusted brands which will be more expensive - but ultimately any ND filter is going to be an improvement (not just for exposure but for polarisation too).
Check you in-body camera settings, there may be other variables in play that are causing what appears to be an over-exposed image.
If you're not already - shoot in RAW. This collects more data and therefore makes it easier to correct an image in post.
Shoot early in the morning or later in the evening ~ see Golden Hour ~ you'll get softer light which will make for better pictures anyway
If you're shooting portraits, try and get the sun behind or at least to the side of the subject.
Potentially more obvious one - look for cover/shade from objects and buildings. Shadows can be just as important to composition as light!
- Get a a non circular continuous ND filter with as many stops as you need and the adapter for your lenses from lee filters.
- And start taking great pictures, properly exposed ones at large aperture, at the beach or anywhere.
- Check their webpage for tutorials, examples and inspiration about what ND filters can do for your photography.
- Remember the saying “Invest in good glass, and not so much in a camera.” Current cameras are just an specific purpose computer that will be obsolete by the time you buy it. On the other hand good glass will outlast you.