Is there any difference between using camera filter and photoshop like software postprocessing?

Question

I can shot using filters such as UV/CPL/FLD or I can get similar effect using software filters in picassa/photoshop etc. Is there special features that can be achieved with post processing?

Asked by yura

Answer

Is there any difference? Yes. You will expose after filtration, allowing your sensor to collect the maximum amount of data. By applying a filter in post, you necessarily reduce the amount of data in your image.

Does the difference matter? Your mileage may vary. I used to take a heap of filters with me, but now I only bring a few specialized ones: circular polarizing, star, ND. I find the data loss does not impact the final image quality, so for me, bringing the extra filters is pointless. You might be an image purist, and if so, you'd want to do your filtration on the lens.

I should say, I use a UV filter mostly as plain glass to protect the lens. This debate rages on, but the difference between images shot with and without are (to my eye) negligible. A circular polarizer is much more interesting, as it actually modifies which light arrives at the sensor. Any attempt to emulate this in post processing is just that: emulation. You will always get better effects and control with the actual filter.

For major color corrections like fluorescent, you have to make the call whether letting more light in and controlling the color temperature in camera or post is better than filtering with a pretty high filter-factor piece of glass. Again, just for me, I correct on the camera and don't use the filter; I correct again in RAW conversion for the final tweaks.

I'm not sure what the question regarding special features that can be achieved with post processing means, but once you get into digital manipulation, the only limit is you imagination. So, yes, there are tons of effects that are digital only.

Answered by Steve Ross

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Screw-in or square filters in the field?

Question

I currently carry a circular polarizer and a screw-in 4X ND with me in the field. I've decided it's time to upgrade my filters, because there are too many times when I really need an 8X ND (or more) and even though you can stack the polarizer, that's not a perfect option.

So I'm looking at what I should be doing in terms of carrying filters in the field. I'm currently leaning away from screw-in filters and towards the 100mm square (aka "Cokin P") filter sets for the NDs, because as you get it darker and darker, focus is an issue, and the square filters are easier to attach after you set up without affecting the rest of the setup.

The other option is the "vari-ND" style of screw in filters. I know the Singh-Rays come highly recommended, but are beyond what I want to spend right now.

So do you carry screw-ins or square? What mounting system do you use? Which brands do you use and recommend? Cokin is decent, but I'm thinking I want to use glass squares and a higher quality than the Cokin filters. Is there a vari-ND in the $100-150 range that is worth evaluating?

Asked by chuqui

Answer

I think you can only get subjective answers on this, different things will appeal to different people. I'll give you my experience.

• I have a polarising filter on my main lenses rather than a UV. If it's low light, or I otherwise don't need it, I remove it temporarily, but it always goes back on. I use the polarising filter all the time, so I don't like to fumble around for it. I don't think I could get used to using Cokin style polarising filters, as often as I use my screw in ones, because it would slow me down I think.

• for ND filters, I do use the 100mm Cokin style. I find they scratch pretty easily, and so I've bought inexpensive chinese ones (Tian Ya). Unless I'm set up to do a lot of images in one spot, I rarely bother to put on the holder - instead I usually hand hold the filter over the lens. The one Cokin style filter than I think is indespensible is the grad ND. It's just not very versatile in a screw in form - graduation is dead centre and you can't move it if your horizon is 1/3 from top or bottom for instance.

• I have considered buying an inexpensive vary-ND. I don't have high hopes that the quality will be that good. Even with Singh Rays you can get vignetting and funny color shifts at extreme densities and with wider angle lenses.

• I find the Cokin style filters are bulky, awkward to carry in my bag, and as a result (apart from occasionally pulling one out and holding it over the lens) they don't get as much use as I'd like. I tend to do a lot of walking/hiking, so I don't tend to take a tripod and take the time to set up properly, so maybe it's just me. If I try to use the Cokin holder and filters I end up fumbling and dropping them, getting finger marks all over them, scratching them. Something to think about before you buy expensive glass ones - all depends on you and how/where you work.

• I have a thin holder on my 12-24mm and I get very slight vignetting in the corners at 12mm. If you do a lot of WA shots, you may want the larger format (170mm?).

• a lot of people I know think Lee make better filters and holders, but I've not tried them out myself.

Answered by MikeW

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Filters in the field? Screw-in or square?

Question

I currently carry a circular polarizer and a screw in 4X ND with me in the field. I've decided it's time to upgrade my filters, because there are too many times when I really need an 8X ND (or more) and even though you can stack the polarizer, but that's not a perfect option.

So I'm looking at what I should be doing in terms of carrying filters in the field. I'm currently leaning away from screw in filters towards the 100mm square (aka "Cokin P") filter sets for the NDs, because as you get it darker and darker, focus is an issue, and the square filters are easier to attach after you set up without affecting the rest of the setup.

The other option is the "vari-ND" style of screw in filters. I know the singh-ray's come highly recommended but are beyond what I want to spend right now.

So do you carry screw-ins or square? What mounting system do you use? Which brands do you use and recommend? Cokin is decent, but I'm thinking I want to use glass squares and a higher quality than the Cokin filters. Is there a vari-ND in the $100-150 range that is worth evaluating?

Asked by chuqui

Answer

I think you can only get subjective answers on this, different things will appeal to different people. I'll give you my experience.

• I have a polarising filter on my main lenses rather than a UV. If it's low light, or I otherwise don't need it, I remove it temporarily, but it always goes back on. I use the polarising filter all the time, so I don't like to fumble around for it. I don't think I could get used to using Cokin style polarising filters, as often as I use my screw in ones, because it would slow me down I think.

• for ND filters, I do use the 100mm Cokin style. I find they scratch pretty easily, and so I've bought inexpensive chinese ones (Tian Ya). Unless I'm set up to do a lot of images in one spot, I rarely bother to put on the holder - instead I usually hand hold the filter over the lens. The one Cokin style filter than I think is indespensible is the grad ND. It's just not very versatile in a screw in form - graduation is dead centre and you can't move it if your horizon is 1/3 from top or bottom for instance.

• I have considered buying an inexpensive vary-ND. I don't have high hopes that the quality will be that good. Even with Singh Rays you can get vignetting and funny color shifts at extreme densities and with wider angle lenses.

• I find the Cokin style filters are bulky, awkward to carry in my bag, and as a result (apart from occasionally pulling one out and holding it over the lens) they don't get as much use as I'd like. I tend to do a lot of walking/hiking, so I don't tend to take a tripod and take the time to set up properly, so maybe it's just me. If I try to use the Cokin holder and filters I end up fumbling and dropping them, getting finger marks all over them, scratching them. Something to think about before you buy expensive glass ones - all depends on you and how/where you work.

• I have a thin holder on my 12-24mm and I get very slight vignetting in the corners at 12mm. If you do a lot of WA shots, you may want the larger format (170mm?).

• a lot of people I know think Lee make better filters and holders, but I've not tried them out myself.

Answered by MikeW

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Why am I getting dark spots with my Singh-Ray 77mm vari-ND filter?

Question

I've been using a Singh-Ray vari-ND with my Panasonic GH1, and I'm seeing obvious dark spots in the image. On a lower setting the left and right side of the image have dark lines and when I go to a maximum setting the dark sides cave into the middle and forming a circles and it looks really bad. I've been using a 20mm lumix 1.7 lens, and I read that the vari-ND shouldn't be used with lenses wider than 35mm in full-frame terms (which mine would be a 40mm after the micro 4/3 conversion) due to the polarized filter. Could this be why? Or is my filter defective?

Note that my hand is slightly in this last image, and is the cause of the darkened upper-right corner.

Answer

The third image looks like vignetting due to the thick Sing-Ray filter and your step down rings. But strange it's only in one corner - you don't have a hood attached do you? You should be able to see this vignetting through the viewfinder.

Even a normal polarising filter is going to result in uneven skies with wide angle lenses, with the sides often being much darker, due to the wide field of view (light coming from vastly different angles through the filter). With variable ND filters, this effect is multiplied.

The solution is using a longer focal length, if possible, cropping out the sides, or reducing the filter density.

The number of stops you can reduce with these filters goes down as the lens focal length goes down. You might be able to reduce 8 stops at 135mm, but only 5 stops at 20mm.

Your 20mm (effectively 40mm) is close to the 35mm limit they mention. It's a gradual thing, so if it's not recommended at 35mm, it's probably not ideal at 40-45mm and you can expect some vignetting or strange colour casts at the edges, and these will move more to the centre of your images the wider you go.

From their website:

NOTE: Due to the nature of the Vari-ND Filter, its "profile thickness" is significantly greater than most filters (14.2mm for standard mount, 10.5mm for thin mount). The profile thickness of either version may cause vignetting when used with wide-angle lenses, especially on cameras with full-frame sensors. Due to the vast number of combinations of cameras, lenses, and other factors, we can NOT predict under what circumstances vignetting will occur, and to what degree. We suggest simply adjusting your focal length, position, and/or composition to remove the vignetting -- use your digital camera's display for reference.

NOTE 2: The design of the Vari-ND Filter may introduce irregularities when used with very wide angle lenses, especially on full-frame cameras. Adjust your focal length and reduce the filter density setting until the irregularities disappear

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SIngh Ray 77mm vari-ND filter spots

Question

I've been using a Sing-Ray vari-ND with my gh1 and I'm seeing obvious dark spots in the image. On a lower setting the left and right side of the image have dark lines and when I go to a maximum setting the dark sides cave into the middle and forming a circles and it looks really bad. I've been using a 20mm lumix 1.7 lens, I read that the vari-ND shouldn't be used with lenses wider than 35mm in full frames terms (which mine would be a 40mm after the micro 4/3 conversion) due to the polarized filter. Could this be why? Or is my filter defective? Any help would be appreciated. Thanks.

Answer

The third image looks like vignetting due to the thick Sing-Ray filter and your step down rings. But strange it's only in one corner - you don't have a hood attached do you? You should be able to see this vignetting through the viewfinder.

Even a normal polarising filter is going to result in uneven skies with wide angle lenses, with the sides often being much darker, due to the wide field of view (light coming from vastly different angles through the filter). With variable ND filters, this effect is multiplied.

The solution is using a longer focal length, if possible, cropping out the sides, or reducing the filter density.

The number of stops you can reduce with these filters goes down as the lens focal length goes down. You might be able to reduce 8 stops at 135mm, but only 5 stops at 20mm.

Your 20mm (effectively 40mm) is close to the 35mm limit they mention. It's a gradual thing, so if it's not recommended at 35mm, it's probably not ideal at 40-45mm and you can expect some vignetting or strange colour casts at the edges, and these will move more to the centre of your images the wider you go.

From their website:

NOTE: Due to the nature of the Vari-ND Filter, its "profile thickness" is significantly greater than most filters (14.2mm for standard mount, 10.5mm for thin mount). The profile thickness of either version may cause vignetting when used with wide-angle lenses, especially on cameras with full-frame sensors. Due to the vast number of combinations of cameras, lenses, and other factors, we can NOT predict under what circumstances vignetting will occur, and to what degree. We suggest simply adjusting your focal length, position, and/or composition to remove the vignetting -- use your digital camera's display for reference.

NOTE 2: The design of the Vari-ND Filter may introduce irregularities when used with very wide angle lenses, especially on full-frame cameras. Adjust your focal length and reduce the filter density setting until the irregularities disappear

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Can I take pictures of the sun without damaging anything? [closed]

Question

Possible Duplicate:
Can the sun damage the camera sensor? Under what conditions?

.. and by that I mean not damaging :

• my eyesight
• my camera
• my lens

I imagine a proper ND filter could allow me but I'm not sure

Answer

A large number of people, both amateurs and professionals, photograph and optically observe the sun regularly. The filters required are well known - a search on 'solar photography' will turn up many references.

Be aware that if you get it wrong you can destroy your eyes or your equipment in moments.
Looking directly at the sun will rapidly damage your eyes.
Looking at the sun through a concentrating lens system allows it to happen quicker, or very much quicker ;-(.

Full daylight is nominally 100,000 lux.
A modern LCD screen on full brightness is typically 300 lux at the panel surface. 100,000/ 300 =~ 3000:1. In practice a 400:1 ND filter will do what you want.

For example, Hoya makes an NDx400 ND filter that is intended for solar photography as well as other applications.

Resulting in -

Above images from here

---

These images are all hot liked to websites. Identify ones which appear liable to be of direct relevance and click the photos to open the link. (Obtained using Google search + images).

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What are neutral density filters and how do I use them to create long exposures in daylight?

Question

I've seen a few related posts on the site but nothing specifically on this point:

I'd like to be able to take long exposure photos during daylight (like the examples in this Flickr group). I'm told that you can do this by using a neutral density filter. So my question is: what is a neutral density filter exactly, and how is it used to achieve that smooth long exposure effect?

Answer

A Neutral Density (ND) filter is a filter that reduces the amount of light captured by the camera evenly across the visible spectrum. As such, it looks grey to black (depending on the filtration power) and does not cast color on the received image (like blue or yellow, e.g., filters will do).

When using a ND filter, there is a need to compensate for the reduction in light by using longer exposures (or higher ISO, but it usually defies the intention of ND filtration). This way, one can capture long-exposure images that are not possible w/o the filter as the camera (set to its lowest ISO and possibly smallest acceptable aperture) is at its slowest speed for a good exposure.

Examples for such situation is when shooting waterfalls in a fairly lit location. Then, the speed for correct exposure is not slow enough to create the required streaming water effect. Using a ND filter, one can reach slower speeds, as if the scene lighting was dimmer.

Note that a uniform ND filter does not change the Dynamic Range of the scene, as the bright areas get darker in the same amount as the dark areas.

Another type of ND filters is the graduate ND filters. These filters usually attenuate the light only at one half of the frame and gradually get clearer on the second half. These filters are used when shooting landscapes, where the sky is much more bright than the scenery and using good exposure for the ground will overexpose the sky. A graduate ND filter lets one reduce the brightness of the sky and get it captured nicely with the ground.

ND filters are marked in multiplies or stops. An 8X ND filter is similar to ND3. Both cut 3 stops of the light. If the camera's meter tells that 1/500 sec is required for the given aperture, then using a ND3 filter will allow an exposure of 1/64 sec with similar outcome.

There are some (expensive) variable ND filters. These are made from two polarizers, where the front element rotates and thus let you set the amount of light being cut (up to virtually no light passing through).

The image below, from Wikipedia, shows the effect of an ND filter:

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