Alley in Pisa, Italy

by Lars Kotthoff

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26

Photography has borrowed the term "gel" (and the technology) from theater. The original colored "gels" were made out of gelatin (and tended to melt). Today, they are made out of other materials that are more heat tolerant (but can still melt....) there's a nice writeup on this on wikipedia: http://en.wikipedia.org/wiki/Color_gel


26

There's a difference between color and color correction filters although they both are colored. Color correction filters are useful in digital photography to get more even exposure in all channels under some special types of lightning. For example you'd probably get more exposure and thus less noise in blue channel if you used blue color correction filter ...


13

Filters for B&W photography are really only applicable for negative film. Here is a good short discussion about this. If you have a digital image you can achieve similar effects in post by manipulating channels during the B&W conversion.


11

Some, yes. Most of the time filters are not needed, but sometimes they can make a visible difference. The reason why color correction filter can make the difference is that on digital cameras color correction is done after the image has been captured to the sensor, and often after it has already been digitized. If the color correction is done before A/D ...


9

This technique is called Selective color. Sometimes, you select a point (in this case, somewhere on the CD-R case), and the region around that point that is close enough to the same color retains its color, while the rest of the picture becomes black and white. Other times, as you mention, you can select a color and a tolerance, or a range of colors, and ...


8

If you are using a digital camera, there is little need to use colored filters, as you can apply their effects in post processing when you do the black and white conversion. See Are there reasons to use colour filters with digital cameras? Also How can using a color filter help to improve a black and white photo? If you are shooting film, then Red is ...


8

Photos made "in the natural way" may be more highly regarded by some, but that alone is no reason to go out and buy a set of filters. There some genuine advantages to working this way, however. For example filtering the light before it enters the camera can prevent overexposure (and hence loss of detail) of one ore more colour channels. This can be ...


8

It's possible to remove the CFA (colour filter array) but extremely difficult. There is at least one company that will do it (Maxmax as asalamon74 states). Doing this is entirely unneccesary for IR conversion, in fact one of the things I like about IR photography is playing with the faint colours that result, which requires the CFA. As to why you'd want to ...


8

Don't use real colored filters on a normal digital camera - for a 15MP bayer sensor camera with a red filter, you would actually be shooting a 3.75MP image. The exception is if you are doing IR or have a sensor modified to do only B&W photography. In general for modern B&W digital photography your equipment is shooting in color, and then you decide ...


8

If you shoot RAW, then there isn't much reason to use color filters anymore. If you shoot jpeg, then you're better off getting it right the first time rather than doing processing afterwards, so color filters are quite useful.


7

Yes, if you want to spend less time behind your computer, attach a color filter on your lens.


6

In general not really. The are potentially some benefits e.g. a blue filter might prevent you from blowing the red channel and getting flare or other problems with excessive light (e.g. sensor bloom) if for some reason you have far more red light. But generally using a coloured filter will just prevent you from changing your mind later compared to using the ...


5

I would say that the biggest advantage of using filters on the camera rather than post-processing in the computer is that you can see the result on the site, making any necessary adjustments. The same goes for in-camera double exposure instead of stacking frames in the computer; you can get immediate feedback on the result.


5

With the flexibility offered by digital image programs such as Photoshop, Lightroom, Aperture, and such, there is no reason to use a colored filter on a digital camera. ND filters and polarizers can obtain effects that aren't possible purely through software, but for adding a color cast to an image there's no reason to purchase or carry around a physical ...


5

Since you shoot RAW. Color-balance has no effect on your photos. If they come out the wrong color, blame the RAW processor or its operator ;) To adjust color-balance of the preview along the Green-Magenta axis go to the camera menu and find the WB Fine-Tuning screen. To adjust it along the Amber-Blue axis, hold the WB button and turn the sub-command dial ...


5

For really good colors you will not get around buyng a color reference card and lighting it with the exact same light as in the aquarium, maybe even submerging the reference. Take the photos in RAW and the software that the color reference belongs to will calculate a profile for the shooting situation. This profile can then be applied to the real photos and ...


5

My best guess is that it may have to do with how the satellite operates. It may capture red green and blue images separately and then combine them. If this is the case, then two things would happen. First, the plane would move between shots for each color. Second, the satellite would move quite a bit as well. While the motion of the satellite could be ...


4

The easiest way to remember the effect of a filter is this: A filter lightens its own color and darkens the complementary color. Here is a link to a color wheel that illustrates the concept. Colors 180 degrees opposite are the complements. So, from the color wheel, we can learn that a green filter will lighten some foliage (foliage does not read completely ...


4

Karel's sample shot has a strong greenish color cast because every "pixel" is processed without weighting, which therefor gives green twice the effect as red and blue. The result is an image processed from minimally amplified pixels, where as normally red and blue channels would be amplified by a factor greater than one to compensate for the greater number ...


4

Your hunch is right: colour cast filters aren't very much use on digital. Many people have a fondness for them from their days using film, but nowadays it's very easy to apply the same effects either by using a warmer white balance setting (e.g. select cloudy on a sunny day - any DSLR will let you do this) or in post-processing (using anything from ...


4

This technique is called "selective desaturation", and you can do it using many techniques. The following guide is for The Gimp, an opensource & free editor for Linux, Mac, and Windows machines: http://www.gimp.org/tutorials/Selective_Color/ You added a "photoshopt" tag, so if you're using that editor in particular this guide might be more of a help ...


4

The camera sensor has a different response to light as compared to the human eye. And as the light over the acquarium has a different spectral composition from daylight, the sensor gets confused. It and the camera try to compensate, change the recorded colour balance as if daylight were falling on it, which of course leads to a distorted colour balance on ...


3

Fluorescent filters are for "converting" fluorescent light to closer to daylight (FL-D) or tungsten (FL-W). Generally speaking, with a digital camera there's not much need for a FL-* filter since you can accomplish the same thing (and more) with your camera's white balance setting. Shooting with film you would want an FL-* or some kind of magenta filter, ...


3

As others have said, ignore color balance on camera, since you shoot RAW. Instead, be sure to shoot a white balance reference at each location. Then, you can use the reference within your photo processing software to easily adjust white balance. I posted a note on my photoblog with instructions on how to do this in Lightroom.


3

If you remove the color filter array then (theoretically) you'll have a B&W DSLR. Removing the filter is quite complicated, there are a few companies offering DSLR B&W conversion like maxmax. Check their webpage they have quite good sample photos.


3

While the posts pointed to by @SteveKemp are good, there is a more general way to accomplish this in Photoshop. Basically, you do this: Duplicate the background layer Use your masking technique of choice to isolate the area that is to be turned black & white. In the case of the image below, Select > Color Range works nicely to select the blue jeans. ...


3

I was in Valencia for the AgEng/CIGR 2012 conference where I saw a presentation about adapting a DSLR to do exactly this. The paper contains the details how to get the best possible Red/NIR colour space for NDVI and shows application of the results. You need to remove the ir cut filter and replace with a ~600nm long pass filter. ...


3

They probably don't correspond to Wratten numbers at all. The experimentally-derived filter factor for the red filter, for instance, is 2, whereas the filter factor for a #25 is 5, so there's an extra stop and a third of light coming from somewhere, and that somewhere is probably in the shorter wavelengths. The other filters are quite similar. That suggests ...


3

Yes, their main purpose is to have different colors on different lights. However in vast majority of cases (if not always) you simply cannot reproduce this setup in post. The human eye is quite good in detecting the natural light falloff and it will detect the things which are Photoshopped, especially if we talk about a setup with multiple lights (we ...


2

To my best knowledge, using strong color filters (like 25A, 38A, 99) on digital cameras have only downsides: You're can very easily blow the channel which color the filter is (red channel if you use red filter) You're underexposing other channels resulting more noise in these channels The result is that you're only using efficiently 25% of your sensor (I ...



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