On Monday I placed an order from
http://www.2filter.com/prices/htpackages.html the following HiTech GND kit.
Qty Name SKU Each Sub Total
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1 Hitech P 58mm 0.9 S.L. Grad Kit HT58GD9S $55.54 $55.54
1 Hitech P 62mm 0.6 S.L. Grad Kit HT62GD6S $55.54 $55.54
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Shipping: INTERNATIONAL $26.50 (6-10 Day Delivery)
Grand Total $137.58 USD
The 0.6 kit is on backorder, expected to take 7 days to fill.
I did lots of reading on POTN about which way to go. My understanding is that Lee / Singh-Ray / HiTech then Cokin is the preferred order of filters, depending on your budget. The Cokin filters aren't neutral and have a grey tint to them which affects the image.
To add to what Glamy and Radar have already typed:
Then you need to choose which size filter you want.
Cokin P = 84mm wide x 110mm height
Cokin Z = 100mm wide x 125mm height
Cokin X = 130mm wide x ???mm height
Soft Edge = Great for horizons that don't have a definate line (eg mountains / buildings)
Hard Edge = Great for flat/ sharp horizons (eg oceans)
The P series limits it's filters to about 77mm lens diameter size. On a 77mm lens you only have 23mm from middle to adjust the filter up and down. So if your horizon isn't in the middle or close to it, then you don't have a lot of room to play with.
The Canon L glass start @ 77mm. I don't have any L, but also didn't want to have to re-purchase all the filters again. This is where I stopped and thought for a long time about which path I wanted to take. The Z series
http://www.2filter.com/prices/Hitech_Z_package.html are more than double the price of the P. I ended up going the P as I just couldn't justify the cost yet of the Z when I don't have L glass. I'll worry about the larger filters when I get to that point.
What I have noticed is that there isn't a lot of original Lee / Singh-Ray / HiTech or Cokin gear on Ebay worldwide. So I'm hoping I'll be able to sell my filters if I want to without loosing too much on them. 2nd hand filter stuff sells very quickly on POTN.
Some nice info here
http://www.2filter.com/faq/techgradinfo.html
Cheers