I know lowering the contrast depends on the developing time which I will do, but I just wanna ask which filter would help with it. I'm thinking of a orange since it smoothens things. The filter is also to protedct my collapsible summicron which is known for having a weak front element. Thanks
There is no filter that will lower contrast across the visible spectrum. An orange filter would darken blues and greens and lighten oranges, yellows and red. In a way this would produce a rather selective change in contrast. Such an effect would be very different from controlling contrast with development. I would suggest becoming familiar with the color wheel if you are interested in using filters.
Are you asking if whether a yellow or orange filter will help increase the contrast in a low contrast scene? Filters darken opposite colours and lighten objects that are same colour as the filter... so they can help somewhat. I only use a filter if I want to darken or lighten something in the scene. If I want to increase contrast, I'll increase development time with perhaps slightly less exposure (depending on how much I want to increase contrast)
A yellow or orange filter will increase contrast, not decrease it.
Increasing/decreasing developing time does change contrast and isn"t influenced by a filter
on the lens.