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I hope this is not considered double-posting -- the same question has been asked under a different thread but didn't get feedback.  I was looking for a GND filter and Bob suggested that square-shaped ones are more useful than a screw-on circular one.  But after some looking around, I wasn't too sure about which one to buy.  Amazon doesn't have too many GND filters to start out with, and Adorama doesn't list the technical details on many of their filters so I can't even tell if a particular filter is screw-on mount or square mount.  I know that Singh-ray makes excellent filters, but they are quite expensive.  So therefore I would like to get some recommendations before throwing in more money.  Thanks.

Not really my specialty, but I know that the Singh-Ray filters have a very good name. They are some form of plastic I believe, but high quality optical plastic. They have a reputation of being very neutral. Yo ucan get them from B&H

Singh Ray 0.6 ND (two stop) grad (http://www.bhphotovideo.com/nitem/IC=SIGND2S46&BI=1066&KBID=1346)

The Cokin filters are also plastic and don't have such a great name for optical quality, but they are cheap and quite usable (if not always neutral).

Tiffen make a line of rectangular glass GND filters. They are called the "P" series. I know they have 84x165mm and 84x100mm filters that fit the Cokin holders. See Tiffen P Series Graduated ND 0.6  (http://www.adorama.com/Refby.tpl?refby=rflAID012417&sku=TFPCGND6). That's a 2 stop soft grad ND, I think they also make 1 stop (ND 0.3) and 3 stop (ND 0.9).

I guess glass filters don't scratch as easily as plastic filters, though they may break more easily if dropped.

Thanks Bob, for these links!  Just another quick question, are 0.6 the most commonly used (G)ND filters?  I am just wondering if I should go with 0.6 or even a darker (0.9) one?

I think the 2 stop (ND 0.6)  filter is the one most commonly used and is usually suggested as the first one to buy.

BTW I forgot to mention the Lee filters are also highly regarded. I think they are also plastic, but like Singh Ray they are optically good and neutral.

for example Lee ND .6 Graduated Neutral Density Filter Size P 84mm x 120mm (http://www.adorama.com/Refby.tpl?refby=rflAID012417&sku=LEPND6G)

It's worth noting that all the ND filter ratings are based on the densest part of the ND grad (i.e. right at the top of the filter. If you do a lot of work with high brightness difference between, for example, sky and land it's possible that a 0.9 ND grad might work better. Most professional landscape shooters have at least of couple of different ND grads (and you can stack them if you have to).

BTW the ND grad I have is the Tiffen 72mm Color Graduated Neutral Density 0.6 Filter (http://www.amazon.com/exec/obidos/ASIN/B00004ZCGW/bobatkinsphotogr). It's a circular screw in type, so it's a bit limiting on where you can put the transition, but since I don't do much photography that calls for the use of grad ND filters, it's easier to carry and it's better than nothing!

Thanks for the follow-up with additional valuable information regarding the GND filters.  The square ones indeed seem much more complex than the screw-ons, that they require holders and adapter rings etc.  I am light-years away from being a pro, and just want to experiment with different things, so maybe I will first buy a screw-on and see how it works and then decide if I should invest around 100 - 200 bucks into the more professional types of filters.

another item to add to my expensive shopping list :-).  Currently it has:

tripod
ball-head
speedlite
full-frame body

If cost is a concern, I really think that this would be better done in software.  Cheaper and much more control.

Then you only need the tripod and ball-head. 8^)

The problem with software is that once you've blown the highlights you can't get them back, so you can't correct a singel shot much You can take multiple images (or at least two) and then combine them (as in HDR), but that requires a static subject (no wind, no waves) or at least one with a static border between the overexposed and normal/underexposed regions.

The static border is pretty much what you need with a gradient filter, too, right?

Not really. You need a linear border, but whatever is in it can be moving since it's just a single exposure. With a soft edged filter it doesn't need to be perfectly linear since the transition from dark to light is pretty gradual.

The advantage of the software method (and multiple exposures) is that it can lower the brightness of small areas in different parts of the frame. However for "normal" grad ND use (sunsets and landscapes), you're usually try just to dim the sky a bit and you have some sort of fairly linear "horizon" line.

I was reluctant to add "adobe photoshop" to my shopping list... because that is very expensive.

I am wondering if someday, the image sensor technology would be so advanced that each pixel on the sensor can be individually configured to different ISO.  so if that can be done, a photography can simply use the LCD viewfinder/touchscreen to specify different exposure level across the frame and thus achieves GND effect, with even much more flexibility (so the border won't need to be linear, and HDR can also be achieved with a single exposure).

You don't need photoshop (in fact I'd go so far as to say that few, if any, photographers really need photoshop). There are other image editors out there that will do 90% of what Photoshop can do for 10% of the cost, and the 10% they won't do most photographers won't really need anyway.

The only real  plus of Photoshop is that like Windows. it's everywhere. It may be expensive and there may be better alternatives, but it's widely supported and can be integrated with all sorts of other software, plus you can buy dozend of books and videos on how to use it (which shows just how complex and difficult it can be to use!).

I use Paint Shop Pro v9  (http://www.amazon.com/exec/obidos/ASIN/B0002W2UMW/bobatkinsphotogr)  myself. Does pretty much everything I need including layers, gradients and masking.  After v9, JASC was taken over by Corel and Paint Shop Pro development has been done by them. Basically they've bloated it, made it slower, dumbed it down and really added nothing of much value. However the latest (?) version, Paint Shop Pro X3 can be found dirt cheap on Amazon:

Corel PaintShop Photo Pro X3 (http://www.amazon.com/exec/obidos/ASIN/B002J9V9BO/bobatkinsphotogr) - $24 with free shipping if you buy something else for $1 or more to make the total $25.

Can't say it's something I'd really recommend, but I haven't used it myself. I do have Paint Shop Pro X2 (http://www.amazon.com/exec/obidos/ASIN/B001EJVQDG/bobatkinsphotogr) and it's OK, but I'd rather have v9. X2 is slower and has a clumsy image browser. It's a real pity that Corel ever got their hands on it. When JASC was the developer it got better with each new version, with Corel it seems to get worse. Then again I believe it was Corel who bought out Picture Publisher. amother early Photoshop competitor. They bought it and killed it off. I still use Picture Pulisher 8 for simple tasks. It's lightning fast. I can open it, open an image, crop it, adjust it and save it before Paint Shop X2 has even loaded!

Thanks for the suggestions, Bob.  I actually used PSP a few years ago for some other purpose (optimizing scanned images for my website, before geosociety was killed off by Yahoo).  But if I am not mistaken, PSP 9 doesn't work on vista.  But I am definitely willing to spend $24 for the X3.  Currently I have been using DPP for processing RAWs, and then use paint.net which is completely free for other stuff.  But granted that paint.net still got some distances to go before it can compete with PSP.

Does PSP have any support for HDRs?

Well, v9 doesn't have any native support for HDR. However I do see that X3 has an HDR merge function. I don't know how well it works. It also has RAW conversion built in but I suspect that the RAW capabilities are probably seriously limited. Personally I always use Canon's DPP for my initial processing of RAW images. It's an excellent RAW converter - and of course it's free.

There are also several free HDR programs which are very good.

PhotoShop Elements will do it, too.

Thanks Keith.  I could be very wrong, but I always thought that anything that has "adobe" on it, other than the acrobat reader, means very expensive. :-) (but of course, I have seen much worse software licensing terms in the fields of statistics and mathematics, that you pay for a fortune to use something for just one year...)

Anyways, for the sake of information completion, here is a link to a page that lists some free HDR applications

http://www.techsupportalert.com/best-free-high-dynamic-range-hdr-software.htm

It basically lists 3 apps:

pictureNaut which as a 4.5/5 rating at the time I found this page  http://www.hdrlabs.com/picturenaut/index.html

FDRToolsBasic, which has a 3/5 rating, http://fdrtools.com/fdrtools_basic_e.php

and

Essential HDR Community Edition, which has only 2.5/5 rating, http://www.imagingluminary.com/Default.aspx

There's also Luminance HDR (which used to go by the name Qtpfsgui). Just by the old name you can tell this is an open source project!

Photomatix used to have a free version, but I don't think they do anymore. It was called "Photomatix Basic". I have it installed on my PC and you might be able to still find the installation program still floating around on the web somewhere. Just Google the name and see what shows up.

cool. this list is super!  so now, the question is what exactly is the difference between HDR and tone mapping?  because some of the "HDR" tools do tone mapping, and my first thought is HDR is like using GND and ND filters to compress the dynamic range of the scenes, but tune mapping is what lead to many cartoon-ish (and aweful looking) pix on the Internet... is this correct?

I think Tone mapping is what you have to do to display a true HDR image via a medium with a smaller dynamic range. The image itself may contain information in areas which differ in brightness by a factor of 1 million, but if the display device can only show differences in brightness by a factor of 1000 you have to modify the tone mapping of the image in an attempt to show the detail in both the bright and dark parts of the image. If you don't then you'll just get a small part of the brightness range displayed along with either blown out highligh detail or no shadow detail (or both).

If the dynamic range of the image is too large and/or you use a tone map that's stronger than you really need, then you get the HDR cartoon look.

would it help if one day the technology for display goes beyond 8 bits per channel?  I think part of the reason why digital photography suffers from dynamic range issue is because we only have 256 values for each channel, so for any intensity in an individual channel, it has to be displayed using one of 256 values.  But if we can add a few more bits to each channel, then we will have 256 * 2 ^ <num of additional bits> to accommodate more ranges.  Of course, at the same time, the physical technology has to evolve as well so on a typical monitor, it can display something much more intense for each channel (and burn our eye sockets out).  not sure about printing though.

This says that a good LCD monitor has 10 bits of dynamic range (How handy that a stop is a bit!)  And the human eye 10-14, so a good monitor can do pretty good.  Raw files, of course have 14 bits or so of dynamic range.

The question is whether the pipe sending the data to the monitor is 8 or more bits.

Of course that 10 bit display would only be 10 bits in a darkened room with the monitor set up properly. Turn the room lights on and you lose the shadows.

What really counts iis the dynamic range of prints, since a print is how most photographs are eventually displayed. I think a print probably has about a 6 bit dynamic range.

Whatever the dynamic range of the captured image, it has to be tonemapped down to about 6 bits to be printed. You can still represent the whole dynamic range of the original but it probably won't look very natural though if you're compressing 20 bits of HDR onto 6 bit paper.