Reddit reviews 52mm 80A Filter

So, normal light (black body spectrum) is a Gaussian distribution of frequencies around a single wavelength. The center-point of this distribution can be moved higher or lower to alter the color of that light as we perceive it. Objects give off bluer (higher-frequency) light the hotter they become, white hot is hotter than red hot, etc. We commonly refer to color spectrums by a Kelvin-equivalent temperature as a result, hence you can buy 'warm white' 3000K light bulbs, 'cool white' 4000K light bulbs, and 'daylight' 6500K lightbulbs.

Now, although our eyes are reasonably good at automatically adjusting to differences in the colors of light sources, so unless we're looking out for it (or it's a big difference), our brain compensates and we just see 'white'. Camera film does not make this adjustment, so shooting under a 3000K light (this is the traditional spectrum of an old incandescent light bulb, so we commonly call it 'Tungsten') with a film meant for daylight (6500K), everything looks yellow. Shooting in daylight with a tungsten (3000K) balanced film, everything looks very blue.

Now, in order to fix this, manufacturers make 'color correction' filters meant to cut out the blue light when you're using tungsten film in daylight, or cut out the yellow light, when you're using daylight film indoors. These are not the same as color filters for black and white.

For using daylight film indoors you need a special blue (wratten 80A to 80D) filter.

For using tungsten film outdoors you need a special orange (wratten 81A-81D) filter.

If you're using a Nikon 50 1.8, you're almost certainly need a 52mm filter. Unlike Leica E39 or other weird sizes, 52mm Wratten filters are really easy to get, and can be had pretty cheap; and super quality is probably not critical for the look you're after.

Here's some (normal color film indoors) cheap filters in 52mm. https://www.amazon.com/gp/offer-listing/B00009V356/