ND filters to increase saturation?

<p>A few weeks ago I was looking at someone's gallery. (can't remember who anymore) a lot of dark pre-dawn landscape stuff I believe. There was a comment about using a 5 stop ND filter to open the shutter longer and "increase saturation" I think it was. I'm pretty sure it was noted that it was a digital capture.</p>

<p>Can someone elaborate on this? I've never heard of such a technique. Is this a hark back to some film saturation thing that isn't relevent with a digital sensor? or something I could consider persuing in my own work?</p>

<p>I know that I graduated ND filter can be used to darken a sky relative to the ground, increasing detail in the other parts of the image. I don't believe that a regular ND filter can increase saturation on its own. It is possible that in that particular scene different parts of the image would be colorful at different points in time because of the changing light and opening up the shutter for a few minutes would allow the camera to capture more time.</p>

<p>There are quite of a few photographers who believe that increased exposure time will indeed increase saturation. From a purely physical standpoint, it is simply impossible. The sensor cannot create colour that isn`t there. The most likely explanation imho is that the darker ND (as neutral as their manufacturers claim them to be) do introduce a colour cast (usually in the magentas). So yes, ND filters increase saturation, but not because they increase exposure time. It would be interesting to do an experiment with the same ND but with exposure times vastly different (say iso100, f/16 and 30 to 120s vs iso3200, f/2.8 and 1/8s )...</p>

<p>By definition a neutral density filter shouldn't create any cast hence the term neutral. I giuess cheaper ND filters might have some cast to them due to the less rigorous production? Certainly ND filters are helpful when a longer shutter speed will create an effect on some kind of motion, but changing saturation.... I don't see that.</p>

Maybe I am missing something, but the only time I have used ND filters was when it was very bright out and I couldn't stop

down enough to get a narrow enough depth of field or when I wanted a longer exposure. Other than letting less light in, I have not heard of any other effect on the

image (film). Am I wrong?

<p><< There was a comment about using a 5 stop ND filter to open the shutter longer and "increase saturation" >></p>

<p>Yes, the saturation can be increased by prolonged exposure with, say, a 5-stop ND filter -- however, the physical properties of the filter has little to do with the saturation.</p>

<p>In the beautiful morning light, where the colorful light and clouds move around, the increased exposure time provides the camera sensor (or film) extra time to record these motions (e.g., from Point A to B, C, D,.. and back again). This often results in a more colorful and saturated image.</p>

<p> </p>

<p>I imagine that an ND filter would decrease contrast, but I'm not so sure that would increase saturation. Maybe what's happening is that all of the colors are getting knocked back down into an easy to observe range. The digital camera will not see color the way our eyes will; it'll only see a subset. Maybe by knocking the contrast down, the photographer is making it more likely that the light that enters the camera falls within that subset; and then, there is an apparent change in the image that is similar to increased saturation.</p>

<p>Yesterday I was out making some pictures with flash in daylight; one of the interesting effects I observed was that a shot from below a plant, strobed, also featuring the sky, rendered a different, deeper blue to the sky than when I took a photo of the sky directly, without any foreground objects. </p><div></div>

<p>Have a look at that sky color, and see this image taken about the same time, with the same equipment. While I would like to think my strobe would illuminate the entire atmosphere, who are we kidding? I think the color changes in the photo above are the result of a change in apparent temperature of the light; a fair amount of the surface area of the image is made with a lamp that's at 5K; but apparent color of local light was different than the normal daylight 5K; add in some contrast compression with the filter, and I think that kind of thing can account for an apparent saturation increase; meanwhile, I know that I did not do any adjusting in post that would have yielded a color change through deliberate editing.</p>

<p>I'm not any kind of expert on the digital cameras, but I think these color shifts are probably some cumulative result that has its influence in contrast compression effects of an ND, in this case black and white Linear Polarizer.</p>

<p>That is, it's not an actual increase in saturation, in bulk; but, an apparent increase (proportionally) brought about by making the colors easier for the camera to record by putting them within the sensor's observable range of color.</p>

<p>Interesting chart on colors and sensor recording midway down this web page: http://digiichi.pentax.jp/english/tech/index.html</p><div></div>

<p>ND filters: that is ND, ND grads and Polarizers (<em>all Polarizers <strong>are</strong> ND filters but not all ND filters are Polarizers</em>) only modify the incoming light.<br>

All ND filters and/or Polarizers slow down (<em>drag</em>) the shutter.<br>

<em><strong>None</strong></em> cause an increase in saturation per se.</p>

<p> </p>

<p>Not all polarizers are ND filters. I have warming/red enhancing and blue/gold polarizers that are definitely not neutral. They do increase color saturation.</p>

<p>An ND filter should have no effect on color saturation by definition. Longer exposures with digital cameras will blur moving objects (cars, water, stars, etc.), and increase digital noise.</p>

<p>Thanks guys! My intuition was telling me this. Look like I'll be sticking with my ND filters for waterfalls only haha</p>

<p><< Look like I'll be sticking with my ND filters for waterfalls only haha >></p>

<p>It's up to you but, why? It can do more, as mentioned by the comments you read about and my explanation above.</p>