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01-21-2011, 01:06 AM   #1
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Gradient and other filter benefits

I read about ND Gradient filters for when the sky is so bright, and that sounds great. However it wouldn't be any better than adding a gradient semi-transparent layer in Photoshop, right? Other than Photoshop taking time (but it takes time to put on the filter and Photoshop seems to have more control).

Also are gradient filters really helpful in other situations, or only when one big area is much different (color/brightness) than the other?

On the other hand, I believe regular solid ND filters do allow the photographer to capture something he cannot add later in Photoshop...? Just trying to understand more.

Thanks.

01-21-2011, 01:39 AM   #2
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Hi,
I found HDR techniques in post processing more useful than a gradient ND filters. Of course this takes some time and required correct captured images.

Solid ND filters and CPLs are my most used.

ND is used when:
1 - I want to open larger aperture and get blurred background.
2 - slow down the shutter speed in bright light (ie. water falls)

ND is used with a flash:
3 - dim a bright background and use flash to highligh the subject, ie. portraits

CPL is used for controlling reflections, sky/cloud.
01-21-2011, 01:48 AM   #3
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Ok, good to know about ND. And I didn't know that's why you do HDR, now I know and look forward to trying it. Thanks!
01-21-2011, 02:06 AM   #4
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QuoteOriginally posted by Kitty Quote
I read about ND Gradient filters for when the sky is so bright, and that sounds great. However it wouldn't be any better than adding a gradient semi-transparent layer in Photoshop, right?
No. What they are doing is reducing the contrast in the scene to something the camera can handle, so you can get detail in the dark areas without blowing out the bright areas. However they have to be used with care to get the boundary in the right place, and IMHO they really don't work (in the sense of producing an aesthetic result) with some scenes as wherever you place the boundary you can see the darkening on something that shouldn't be darkened.

01-21-2011, 04:46 AM   #5
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Good information above. Reality has greater dynamic range (DR) than human vision, which has greater DR than a digital sensor. One of the eternal challenges of photography is to compress the DR of reality down to a recordable range. If you have time and tripod, then HDR techniques are excellent. If you must shoot handheld or otherwise take single shots, then optical filters do the trick. Their effects can NOT be replicated in PP -- shooping layers can't add details that were never recorded.

Some optical filters:

* Polarizing (PL) and Circular Polarizing (CPL) filters reduce glare and reflections, and increase sky contrast. Two CPL filters, or a CPL+PL combination, act as a variable ND filter, but can introduce unwanted color at extreme occlusion.

* Neutral Density (ND) filters reduce the amount of light hitting the frame (film or sensor), extending exposure times. Extreme ND's manipulate time -- in long exposures, anything that moves, vanishes. Graduated ND (GND) and Split filters have one half clear, one half darkened. I have some split colored (Vivitar HalfChrome) filters that are half clear, half green or orange, for applying partial filtration for B&W shooting.

* I guess this is the wrong time to rant about filter-like +dioptre closeup lenses, split closeup lenses, IR-pass filters, use of B&W and CC (color correction) filters in digital photography, etc.
01-21-2011, 04:51 AM   #6
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QuoteOriginally posted by RioRico Quote
...optical filters do the trick. Their effects can NOT be replicated in PP -- shooping layers can't add details that were never recorded.
Even in the case of a GND? It was just darkening parts. I was talking about darkening in photoshop.

Cool about Extreme NDs.

QuoteQuote:
* I guess this is the wrong time to rant about filter-like +dioptre closeup lenses, split closeup lenses, IR-pass filters, use of B&W and CC (color correction) filters in digital photography, etc.
I'm curious about the B&W and CC, closeups lenses, etc. I don't know what IR-pass filters are.
01-21-2011, 04:56 AM   #7
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Grad NDs are a crude way of equalising exposure between a bright sky and relatively darker foreground. Limitations already mentioned make it less favourable than other methods, but before the digital age, it was reasonably well used. It is, however, better than just adding a gradient in PS after the shot as you'll have significantly more highlight clipping from a straight shot than you would with a filtered sky - unless the sky is exposed for and there is enough shadow detail in the foreground to enhance in PP.
01-21-2011, 05:08 AM   #8
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Oh, right about the sky. That's what RioRico meant, but I wasn't catching on.

01-21-2011, 05:16 AM   #9
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I use ND gradient filters in two ways, the "normal" method of darkening sky in relation to the rest of the landscape, and I also use them in waterfall shots when the white water of the fall is significantly brighter than the rest of the shot. This is different than using a solid ND filter to slow shutter speed down. Note that you can get two different types of ND gradient filters; one where there is a sharp demarkation between the ND and non-ND halves of the filter and one were there is a gradual transition between ND and non-ND halves. The latter type give me much better results.

NaCl(don't use them often but they are much better than PP in certain situations)H2O
01-21-2011, 11:16 AM   #10
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QuoteOriginally posted by Kitty Quote
I'm curious about the B&W and CC, closeups lenses, etc. I don't know what IR-pass filters are.
Ash and Salty are dead-on. As for the other stuff:

* There are two sorts of close-up/macro adapter lenses (strap-ons): 1) complex, corrected adapters like the Raynox products, and 2) simple cheap filter-like +dioptre meniscus close-up lenses. Both (1) and (2) shorten the working distance; (1) correct for aberrations, while (2) degrade image quality somewhat, especially at the image edges. If edge sharpness isn't important, they're cheap fun. I'll use a +1 on a slow lens to drastically thin the depth of field (DOF).

* I mention those +dioptre strap-ons because they also come in split versions similar to graduated or HalfChrome filters, where half the 'filter' is clear glass (or blank) and the other half is the close-up meniscus. This can apparently thicken the DOF -- focus on a near subject through the lens portion, and on a distance through the clear/blank portion. As with any gradated or split filter, be careful where that terminator line goes!

* IR-pass (aka IR) filters block some or all visible light and only allow InfraRed frequencies to pass through to the camera. These filters work best with a camera that has been modified to remove its internal IR-block hot.filter. An unmodified camera requires long exposures with most IR filters.

B&W (Red, Yellow, Orange, Green, Blue) and CC (color-correction) filters are mostly irrelevant on unmodified digital cameras -- their effects CAN be replicated in PP. Exceptions:

* I have read that a Red filter increases sharpness slightly when shooting B&W on a digicam. This has to do with the construction of microfilters built onto the camera sensor. I haven't verified this yet.

* A Yellow filter when shooting garish neon lights at night gives strange color renditions. Since used sets of B&W filters are cheap, this can be more cheap fun.

* B&W filters can be stacked on modified digicams for interesting tonal effects. I use these on Sony NightShot P&S's, which are pre-modified to disable the internal IR-block hot-filter.

* I use a Blue B&W filter or a Violet CC filter as wayback machines. The earliest photo emulsions only saw Actinic light (UV, Violet, Blue) and were blind to green, yellow, orange, red, and IR. Blue and Violet filters let me replicate pre-1875 photo visions.

Using these tinted optical filters is Spectrum-Slicing. More sophisticated variants are the filters used in forensics and scientific work, where narrow bands of the EMF spectrum can be closely examined. Shooting in UV slices can require special (rare, expensive) lenses, beyond my budget. Ratz...
01-21-2011, 12:45 PM   #11
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QuoteOriginally posted by cats_five Quote
However they have to be used with care to get the boundary in the right place, and IMHO they really don't work (in the sense of producing an aesthetic result) with some scenes as wherever you place the boundary you can see the darkening on something that shouldn't be darkened.

Yep. Here's a pic where I used a graduated ND filter to tame down the sky. It worked fairly well, but you can see the filter line on the tree trunk.

https://www.pentaxforums.com/forums/members/taomaas-albums-video-stills-pictu...ave-chair.html
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