Explain the GND filter to me

Discussion in 'Digital Photography' started by Puckman, Sep 18, 2013.

  1. Puckman macrumors 6502

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    #1
    I keep seeing sunset/landscapes taken with GNDs, posted by others. I've used a CPL filter to do some landscape shots (with mixed results in cases of wide angle lenses) and I get how they work and why one would want to use them.
    I don't quite get GNDs. Can someone here explain it to me?
     
  2. Prodo123 macrumors 68020

    Prodo123

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    #2
    Normally in a landscape shot the sky is too bright while the land is too dark, owing to the relatively low dynamic range of the camera. Since we can't make the ground brighter, instead we use a graduated ND filter to darken the sky for a more even exposure.

    One example would be when the sun is in the frame; that would either give the ground proper exposure while blowing out the sky, or black out the ground while properly exposing the sky.
     
  3. Phrasikleia macrumors 601

    Phrasikleia

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    #3
    Prodo123 summed it up well. I would just add that GND filters are increasingly going the way of the colored filters that were once standard for B&W photography (i.e., they're going the way of the dodo). I personally stopped using my GNDs about a year and half ago, and most of the landscape photographers that I know have ditched theirs as well. The alternative is to create the digital equivalent by blending together differently processed iterations of a single raw file, or in the case of a scene where the dynamic range is very high, to blend separate exposures.

    The benefit of using an actual filter in the field is the instant gratification you get: it allows you to see the darkened sky immediately, right on the LCD screen. The drawbacks are many, however. Most importantly, the darkening runs in a straight line across the filter, so even with the "soft" versions, you will typically get areas of unwanted darkening. It's a rare scene that has a completely straight line where the dark land meets the sky--even seascapes often have cliffs, rocks, or sea stacks overlapping the horizon. You can of course use software to edit out that unwanted darkening, but it's usually far more difficult and time consuming than just doing a basic blend as I described above.

    Furthermore, the filters are just fussy to use, especially when time is short and the light is changing quickly. They are kind of fun to play with at first, but it gets old pretty quickly. And, as the old mantra goes…why stick an extra piece of resin or glass in front of your expensive lens if you don't have to?

    That said, you do need to balance the cost of the filters and the holder against the cost of the software substitute (e.g. Photoshop), if you don't already own something that can handle that kind of editing.
     
  4. Prodo123 macrumors 68020

    Prodo123

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    #4
    But there is also the upside of retaining the full dynamic range of the image. What was unintentionally darkened by the GND can easily be recovered in post without much loss of detail, since every part of the image has the full dynamic range instead of one part being blown out or darkened out.

    And yes as Phrasikleia mentioned they are fussy to use since you have to move and adjust the filter to the perfect position. These are not your everyday circular thread-on filters; thread-on GNDs defeat the point of GNDs. No, these are the big square filters that take up much more space but also offer a bigger degree of adjustment. If you can deal with that then by all means go ahead.
     
  5. Puckman thread starter macrumors 6502

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    #5
    Got it! Thanks all for the clarifications.

    I guess I've been doing the poor-man's version of exactly this when I use the Graduated Filter option in Lightroom to darken the sky in those landscape shots where it's blown out.
    I say poor-man because that too requires somewhat of a staight line to be drawn across the photo, as opposed to doing something more accurate via PP or similar.

    Thanks again! Very informative!
     
  6. Phrasikleia macrumors 601

    Phrasikleia

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    #6
    I'm not sure I'm following you here. Whether you use a GND or blending, the goal is always to retain the full dynamic range of the scene. And I would not say that removing unintentional darkening is an easy task; as I said above, it's actually more difficult than doing a blend because you're then having to mask out areas much more selectively. Sorry if I've misunderstood you.

    Yes, it's exactly the same thing as using a GND as far as the straight line goes, but the GND will compress more of the scene's dynamic range into the final image.
     
  7. phrehdd macrumors 68040

    phrehdd

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    #7
    Graduated filters are a great tool when for certain types of shots. As some mentioned, they fall a bit short if your subject area has items that cause an irregular horizon line or similar. - Example being a nice field with a water tower sticking up into the sky. The graduated filter would serve the sky area well but then your water tower is now irregular in exposure with part of it being within the dark area of the graduated filter.

    Alternatives to the above and other similar situations are many and it depends on what you want to do.

    1) Use a polarizing filter but do not bring it to its full ability but just enough to darken the sky. Consider then post process work (burn in the sky a bit more or equivalent process).

    2) If you are using a tripod, consider multiple exposure and then overlap in post processing. This does come with challenges as any item that moves will not be sharp and wise to use a good software to help with this process to get the HDR impact. Just remember clouds do move as do plants and such in the wind. No additional software is needed in such application as Photoshop as you create layers (each exposure) and then bring forward the parts you want to keep. - See any PS forum for a how to on this.

    3) Some cameras do well with high dynamic range and it is wise to learn about this ability and practice using it. There will be some post processing required to finish this process.

    Additional - learn about masking in post processing. Done properly it will pretty much allow for some very impressive results allowing you to darken the skies even if the horizon line plus objects is irregular.

    My quick and dirty PS play - If I know that the range is a bit large in terms of darks to lights, I'll do three exposures. When reviewing the files for each, I'll grab one to use in a test. The test is pretty simple with the right post software program - I'll copy the file first and use that and then adjust all exposure for the below sky area and do colour adjustment. I'll repeat the process and do the same except for the sky. When completed, I then take both end results and put them into a new project where they are treated as layers and do similar to what I did above where I allow the best of both worlds to come through and then save. It really doesn't take very long to do if you practice. I usually (because it is just a test) can finish the entire exercise in a matter of minutes (3-5 minutes on the average).

    My only concern about graduated filters is related to position of the sun and knowing to be careful about flair/reflection and of course, making sure that filters are kept very clean (learn how to clean filters properly). One area where graduated filters can really be fantastic is on some types of longer exposures as the more compressed range gives some flexibility.
     
  8. Puckman thread starter macrumors 6502

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    #8
    Again, very informative, thank you!

    I have to admit, I barely do much post work as I tend to focus more on the fun in taking the photos.
    I've barely tapped the capabilities of Lightroom (mostly use it to fix exposure if need be, improve contrast on the image as a whole, fix highlights and shadows if need be and that's it).
    I need to spend some time learning about creating masks (Is that even possible in LR? Or does one need something like PS or Pixelmator?) and take my post abilities to the next level.
     
  9. Laird Knox macrumors 68000

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    #9
    You can't use masks in Lightroom but it does allow you to use brushes. However to really take advantage of the technique you need a good photo editing program. LR can do a lot these days but you really want layers and selective editing tools.
     
  10. Phrasikleia macrumors 601

    Phrasikleia

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    #10
    Once again I'm having trouble following a reply in this thread. I'm not sure what you mean by "any item that moves will not be sharp." If you use the right shutter speed to arrest movement, then it should be sharp. Or are you referring to the blending process? If so, then you just have to shoot with movement in mind and carry out the blend accordingly. If you're using software that automates things, then all bets are off--you then have very little control over how the different exposures come together; but if you do the blending manually with luminosity masks and layers (a very quick process once you get the hang of it), then the world is your oyster.

    Photoshop really is best for blending because it gives you the most control over creating masks. I believe there are plug-ins that you can get for Lightroom that will enable some automated masking effects, but they will be quite crude by comparison with what you can do in Photoshop.
     
  11. phrehdd macrumors 68040

    phrehdd

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    #11
    Things that move - clouds, trees in the wind or for that matter any flora when there is a wind.- Cars, people, waves in the ocean. These are all things that one should watch for when doing a composite of same image multiple files. A friend of mine got a rather interesting situation of 3 long exposures before sunset. The shadows were rather odd making an outside shot look like multiple strobes or large reflectors were used poorly.

    I agree with your statement about using Photoshop or similar (Lightroom with plug in/filter).
     
  12. Phrasikleia macrumors 601

    Phrasikleia

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    #12
    Right, things are nearly always moving in landscape scenes. If your friend is getting the effect you describe, I reckon he just needs to hone his shooting or blending skills a bit more. The idea that "any item that moves will not be sharp" is just not true. I've done blends for scenes with gale-force winds blowing foliage, clouds, and water around. You just have to blend by hand from exposures that were shot with motion issues in mind.

    For example, in areas where foliage overlaps sky, just shoot to freeze the motion and to expose to the right (without clipping) so you can double-process a single raw file for that transition area (darkening the sky is easy on the pixels that way). Then shoot a separate exposure for the darkest shadows (which will almost invariably be lower in the scene, not up near the light). In your blend, you just select the right bits for each area. Do not try to use all of the frame from each different exposure and mush it all together; just edit in the parts that you need so you won't end up with ghosts or blurry areas from unnecessary superimposition.
     
  13. Apple fanboy macrumors P6

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    #13
    OnOne software works quite well for masking and layers. You can download a free trial for 30 days so its worth a look to see if you like it and can get on with it.
    I'm sure Photoshop is the best, but not the cheapest option.
     
  14. Puckman thread starter macrumors 6502

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    #14
    Yeah. Unfortunately I don't own PS. I've considered making the purchase, but would rather spend the money on new lenses :)

    I do have Pixelmator and will have to see how well it does for things like this.
     
  15. MCAsan macrumors 601

    MCAsan

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    #15
    hardward GND are a very bad idea. Back in the far distant past, there was this thing call film. You had to capture a scene in the analog world of light sensitive chemicals and a papers.

    But today, thanks be to God, we do not have those analog limitations. We can vary easily capture all the range of the scene without throwing away data (which is what any filter does in the digital world). So collect and keep all the data can get from the mega dollars or equipment you have.

    To get around the current digital camera sensor range limits....make multiple shots and merge them with one of several different techniques (HDR, layer merging...et.) Heck even smartphone cameras are doing HDR to get past the sensor limits.

    A couple of things about filters: they cost money (good ones are expensive), they can get lost or damaged, one size does not fit all (lenses),, and they take up space in bags and pockets. So spend money on the only common filter than can not be replicated in post processing software.....circular polarizer. Leave the other filters at the store.
     
  16. bking1000 macrumors 6502a

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    #16
    This conversation covers a wide range of the pros and cons, so not much to add.

    Other than to say, you can buy the Cokin-type square GND. If you are doing slow, tripod work, you can then free-hand position the GND to have the gradient land where you want it.

    You have, of course, discovered the problem of CPLs with wide angle. BTW -- if you are using a camera that is NOT a DSLR (say, one of the mirrorless cameras), you don't need a CPL. You can just use a straight up polarizer. This can sometimes be cheaper. I think they could also be a bit better quality, though I don't have a reference anywhere for that.
     
  17. acearchie macrumors 68040

    acearchie

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    #17
    If you want to see if a GND is something that you would be interested in then there is a quick way to create a fake one.

    Get an exposure of 10 secs or more (for ease of use).

    Place your phone/hand/piece of paper over the lens blocking out the sky (assuming the sky is the brightest part of the image) then take the picture.

    After a few seconds have elapsed (5 is a good starting point with a 10 second exposure) remove whatever you used to block the lens and allow the exposure to finish and 'Hey Presto!' you have created your own fake GND!
     
  18. flynz4 macrumors 68040

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    #18
    I too have stopped using any filters except the CPL. Instead I'll typically shoot 3 shots using the bracketing function of my cameras.

    Generally, I'll use an HDR program to blend the three images... usually NiK Software HDR EFEX... but often I will use NIK Color EFEX filters instead. I really try hard not to overdue the "HDR effect"... as I do not think it looks good if overdone. It is not unusual for me to re-do a post processing step because what I thought was "just enough" HDR originally, felt too strong after the fact... probably weeks or months later.

    /Jim
     
  19. themumu macrumors 6502a

    themumu

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    #19
    Don't want to beat a sick horse, but you guys are so negative about this little tool, I had to chip in ;)

    I still keep my round GND filter close by, on some trips mounted more often than not. While I do agree with many points made here about the shortcomings of this filter, it's a matter of what kind of compromise you are willing to make.

    I'm not a pro, and I only shoot for fun and for good memories, so I often try to reduce my shooting workflow as much as sensibly possible. I don't take a tripod with me unless I go out for some star trail type shooting (hasn't happened in years). I do software development for a living, so I cannot stand the thought of spending more hours on a computer retouching photographs - so I don't keep RAW files to avoid the temptation. Most photos I share online go straight from camera. Some get extra 20 seconds to straighten the horizon, crop, and/or do some mild colour/highlights/shadows adjustments. A circular GND fits me well, even though it's not perfect.

    A point made about in-camera dynamic range enhancements is worth re-iterating though. It depends on the camera how well it actually works, I have found my D7000 to be less effective and too conservative in it compared to say, Fuji X100s.
     
  20. Puckman thread starter macrumors 6502

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    #20
    Hah! The part about being a software developer and not wanting to spend any more time in front of a computer totally resonated with me.
    I'm a developer too. I find myself doing everything possible to minimize the time I spend in PP. Which is one of the reasons I have such a hard time getting some of these amazing end-results I see on here (the other reason being that I am not all that great a photographer, haha).

    So, does this mean you shoot in JPG? I have tried that once or twice and just did not like what came out of the camera. I still rather spend the 20 seconds in LR (yes, 20 second per photo is about as long as I can stand) adding a little contrast and clarity. I think that still looks better than 90% of the JPGs coming out of my camera.
     
  21. themumu macrumors 6502a

    themumu

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    #21
    I crank the hell out of the saturation/vibrance/contrast/whatever settings in camera and what comes out usually satisfies me. It takes a little while to figure out the best settings when I get a new camera, but then I keep shooting that way for a few years. On the Nikon DSLR the settings can be cranked hard enough that I think they are too much, although on the x100s it seems even the max can sometimes be a bit too conservative. Just experiment :)
     

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