Filters and film

[ReeRay]

Having just returned to shooting film (emphasise on colour slide) after a very long lay off I wonder, in this digital/Photoshop age, if filters still play a part. I can appreciate the use of a polarizer and UV/haze (protection) but wonder what, if any, would be the use of warm up and correcting filters when it seems to me this can be performed with software. I'm not talking B+W here, just for colour.

Am I missing something?

just realised maybe in the wrong section - could admin move please

 

[carstenw]

For the best quality, you will still want to use filters. Correcting dramatic colour casts would put a strain on the available data.

 

[ReeRay]

Thanks for that - it makes sense.

 

[carstenw]

Interestingly, the same problem occurs in digital, but is more or less ignored, due to the generally high level of quality. Doug Peterson has also pointed out a few times that correcting tungsten colour casts in software puts a real strain on the image data, and it might be better to correct before the sensor with a tungsten filter. The problem is that the yellow light has an underrepresented blue channel, yet this is the very channel which is boosted to correct the cast in software; a double-whammy, so to speak, and exactly the reason why the blue channel often looks so noisy compared to red and green.

I did some tests with a tungsten filter, and sure enough, the improvement in the blue channel was equivalent to about 1 stop of ISO change, i.e. the blue channel at ISO 320 on a Leica M8 with a tungsten filter had almost the same quality as the same channel in ISO 160 without the filter. Almost. Unfortunately, the filter cost about 1 stop So the whole thing makes little sense, except if you are at base ISO on a tripod and want a small blue channel improvement.

 

[dougpeterson]

Interestingly, the same problem occurs in digital, but is more or less ignored, due to the generally high level of quality. Doug Peterson has also pointed out a few times that correcting tungsten colour casts in software puts a real strain on the image data, and it might be better to correct before the sensor with a tungsten filter. The problem is that the yellow light has an underrepresented blue channel, yet this is the very channel which is boosted to correct the cast in software; a double-whammy, so to speak, and exactly the reason why the blue channel often looks so noisy compared to red and green.

I did some tests with a tungsten filter, and sure enough, the improvement in the blue channel was equivalent to about 1 stop of ISO change, i.e. the blue channel at ISO 320 on a Leica M8 with a tungsten filter had almost the same quality as the same channel in ISO 160 without the filter. Almost. Unfortunately, the filter cost about 1 stop So the whole thing makes little sense, except if you are at base ISO on a tripod and want a small blue channel improvement.

Exactly right. Though less important when using a digital back where the ability to accomplish a virtual "push" on the blue channel will result in little noise until that push becomes more than 2ish stops (depending on the DB and software used). Still, nothing beats an image where the red/blue/green see properly ratios of light. Filters > No Filters

Doug

Doug Peterson, Head of Technical Services
Capture Integration, Dealer: Phase One, Canon, and Other Photo Brands | Personal Portfolio

 

[Jan Brittenson]

Whether it's an improvement to color adjust using filters and turning up the sensitivity or increasing exposure to make up for it, really depends on the camera and what you're correcting for. There's only one way to find out really, and that is to try it for yourself in your particular situation.