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Author Topic: HDR/Exposure Blending or Graduated ND Filters  (Read 8142 times)
kuau
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« on: May 30, 2009, 03:56:42 PM »
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With how good Exposure Blending and HDR has become for digital images, Do many people still use Graduated ND filters anymore?
Just wondering before a go out and spend a bunch of money on a Cokin Z systems and filters. Basically at what point is is better to do things in PP as opposed to using filters on front of the lens?

Steven
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bill t.
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« Reply #1 on: May 30, 2009, 04:58:29 PM »
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Quote from: kuau
With how good Exposure Blending and HDR has become for digital images, Do many people still use Graduated ND filters anymore?
Just wondering before a go out and spend a bunch of money on a Cokin Z systems and filters. Basically at what point is is better to do things in PP as opposed to using filters on front of the lens?

Steven
In post processing it is impossible to restore a completely blown out cloudy sky.  So in theory if you want to only shoot a single exposure the graduated ND will at least preserve information in the sky that you can then further post process if you want or just leave as is.  But if you can shoot an exposure bracket (preferably from a tripod) you can use blending, HDR, or just simple masks to superimpose the correctly exposed sky over the landscape in a way that can look natural or surreal to your liking.

Purists will consider either method forced and artificial...you should have waited around for the right sky, weather, and lighting conditions.

Either method can look hoaky, but ND skies almost always look goofy IMHO, especially if a colored filter is also in play.  Graduated color filters are just evil.  And with any filter or optical accessory used at shooting time, there is always the danger that it will be so misapplied or misaligned that an otherwise good shot is lost...that's the biggest argument against devices

Personally I use exposure blending on 90% of my landscape stitches to simply convey how the sky and shadows were perceived by my brain, and once in a while add a transparent PS gradation over an existing sky to smooth it somewhat or fix a too-bright sunward corner.  But I have never imposed a "stock" sky on an important image, which is another highly abused technique.  Well maybe once.
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Ancient City Photo
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« Reply #2 on: May 31, 2009, 07:51:03 AM »
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I do both if needed.  

I've used filters to better control the light that is available and then I shoot a series anyways.  It will blend better than having some of the images so grossly blown out because of the sky when exposing for the ground.  You get to much bleed sometimes.  I find the HDR just doesn't always blend as nicely.



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amcinroy
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« Reply #3 on: May 31, 2009, 10:01:26 AM »
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HDR of moving water is troublesome, particularly where exposures are between 1/30th of a second and 10 seconds.
Long exposures of moving clouds also causes problems

To solve these problems, grads make a lot of sense.

95% of the time I use grads. It can often reduce the post-processing time from 30mins to 3 mins.
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Andy McInroy Photography
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enlightphoto
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« Reply #4 on: June 04, 2009, 12:13:37 AM »
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Same question asked on another forum; this was how I answered:

At the risk of sounding a bit none too modest, I like to think of myself as an
accomplished landscape photographer. To that, I absolutely still use my set of 4
GND filters when in the field. The short answer; 10 seconds in the field, or 10
minutes behind a computer.

Both filters and photoshop are tools, and one doesn't nessecarilly replace the
other just because they can be used to perform similar functions. Just because I
used GND filters in a particular shot, it doesn't mean that I won't also use
photoshop to add to, or further refine the GND effects I brought home from the
field..

In my current landscape portfolio at:
http://www.enlightphoto.com/webpages/landp..._Photos_01.html

I have 10 digital images that used GND Filters in the field, and zero that are
pure PS Blended exposures. 4 of the 10 have used mild application of local ND
thru Photoshop in addition to what was available by use of using filters in the
field. The rest are just fairly straight conversions of the RAW file. The most
common reason I add ND in PS is to control a highlight area, or further open up
a shadow area - the same reasons I use the filters in the field.

HTH & Cheers,

- Gary.
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Gary Crabbe
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JeffKohn
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« Reply #5 on: June 04, 2009, 03:09:08 PM »
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I suppose grad filters can be quicker for those who don't like to spend post-processing time on the computer. If you have to get your image with a single exposure they can be a big help. I'd rather spend a little extra time at the computer instead of having to mess with grad filters while shooting in the field, but that's largely a matter of personal preference.

The biggest problem with grad filters is the lack of flexibility in placing the transition zone. With a level horizon it's not really an issue; but when you have an uneven horizon the use of the grad filter becomes more obvious. Mountains, trees, and other object that stick up into the sky end up getting unnaturally darkened. Depending on the filter strength needed, this may not be too objectionable, but for some compositions it just looks awful IMHO. Film shooters didn't have much choice (especially when shooting chromes), so they learned to deal with the limitations (favoring certain composition types, passing up on certain scenes with the dynamic range is just too great and a filter won't work, etc). But with digital we have additional options.

When digitally blending bracketed exposures, I have much more flexibility and control over how to do the blend. There are several techniques that can be used, from simple layers with gradient masks, to automated processing such as HDR or exposure fusion, to completely manual blending with layers and complex masking (or any combination of these). Yes, some image types will take quite a bit of work to get a truly seamless result; but those same images are the ones where getting a seamless result with grad filters is impossible.

Movement in-between bracketed exposures can be a problem when using just HDR Tonemapping or exposure fusion. But with the manual, layer-based approach that I use most often it's rarely an issue; only when the movement takes place in the 'transition zone' do you have a problem, and even then it can almost always be fixed with some careful masking (or as a last resort, cloning).

Moving water can usually be handled quite easily in the case of streams, rivers, and waterfalls. Exposure fusion handles these situations pretty well in most cases. For the cases when it doesn't (rolling waves on the coast, for instance), it's just a matter of making sure those areas are masked so that they come from a single exposure.

The hardest part of manual exposure blending is when you need the transition to occur in an area that has high-contrast edges. Simple exposure blending with masks or gradients will often produce halos or other unwanted effects. HDR Tonemapping also has problems with halos. Exposure fusion usually comes to the rescue in these situations. Exposure fusion as found in enfuse or Tufuse Pro essentially does pixel-level exposure averaging that's weighted for mid-tones. (That's a gross over-simplification, but you get the general idea). This works very well for high-contrast edges. Often times what I'll do is run my bracketed exposures though Tufuse Pro to generate my 'base' layer, and then use the original exposures as additional layers with masking to improve the overall image. Using the Tufuse image as the base layer makes getting seamless transitions between exposures much easier.
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markhout
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« Reply #6 on: June 05, 2009, 08:31:09 AM »
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I second Jeff's comments. In practice, I make sure that I bracket images and then merge two exposures when needed (i.e. not HDR tonemapping, just merging sky and foreground). Also, I make sure to leave some leeway for RAW processing the same image twice, 1 or 2 stops different.

Mark
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Bill Lawrence
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« Reply #7 on: June 05, 2009, 06:18:23 PM »
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I use both techniques.  GND filters are great when shooting the 4x5 (or other film) - scanning and trying to register the images are a pain.  Blending is great when your cutoff isn't an easy straight line (or close to) as delineated by your filter.  OTOH - Blending is a real pain with motion in the image, such as plants in the wind.  Personally, I bring a set of GND filters with me, use them if I'm using my 4x5, and plan to blend if I am using my DSLR, unless there are motion issues (if so, then back to the GND).

Cheers!
Bill
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