jimmyt wrote in post #17395037
Please give me some advise the right one for me
What are you wanting to do exactly? In order to help you with what you need to do the job, we need to know what the job actually is. You only say that you want to be able to use f/4 in strong sunlight.
There is no problem using f/4 in direct, bright sunlight for setting DOF, it just needs a shutter speed of around 1/1600th at ISO 100. No need to use a filter to allow you to use any aperture, and therefore DOF, you want, so you don't need anything to help you do that.
Are you specifically wanting to use a slow shutter speed? If so, that is a completely different situation to the one you mention (where you just say you can't use big apertures). If you are wanting a slow shutter speed, what speed do you need to get down to? Are you just wanting to get down to 1/200th to allow flash synch for fill flash, maybe 1/80th to get good prop blur with aircraft or background blur with racing cars, or do you want to go really slow (maybe a second or two or longer) to blur waterfalls etc.?
In order to know how dense a filter you would need to get a certain shutter speed at f/4, you need to calculate how many stops slower you need to go, then select a filter that gives you that amount of adjustment.
Also keep in mind that a CPL alters the image, in terms of reducing reflections, deepening blue skies etc., and a ND filter doesn't, it simply reduces light getting into the lens. Variable ND filters can have problems when set to the higher densities (often a cross will appear in the image as the density created by the two polarisers varies across the frame) particularly with cheaper, lower quality filters. Some ND filters, again particularly the cheap ones, can have colour cast issues.
Tiffen do not come to mind as one of the quality filter manufacturers. In fact, they are generally a pretty poor quality product.