wow.....

Robbo

Robbo

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Grad nd filters are alot more expensive than I thought!

anyone know why?
 
Big_Ham said:
Because to get the filter to be of a quality where it wouldn't distort the image costs a bit?
Click to expand...

I know but one I looked at was £130 ....... even a 77mm B+W 10 stop is only 80.

Didnt know if they are harder to make for some reason
 
Robbo said:
I know but one I looked at was £130 ....... even a 77mm B+W 10 stop is only 80.
Click to expand...

Which one was that? Singh Ray?

Lee ND grad filters are about £60 and Cokin P series under £20. You pay your money and you make your choice.

Getting a genuine neutral tone is quite difficult, especially when it has to vary in density in a a controlled manner.

I was chatting the MD of the manufacturers of the glazing for The Shard skyscraper at London Bridge the other week and he was explaining that it's incredibly difficult (and expensive) to get a neutral colour tone on glass.
 
its about pigment control. A plastic ND filter is made with a dip process - the blank is dipped in dye, that is hot for a determined amount of time. Getting the correct transmission, with no colour cast is very difficult. To top that, as the filter absorbs the dye, the solution has less dye in it, and the next filter takes the dye up at a different rate

If a surface coating is used, then if scratched, you have no filter where the scratch is

If the filter is then sent for a MAR coating, the coating process has a reject rate

If the filter is "cast" or pressed, the reject rate is high too, as surface blemishes are very hard to control. If the filter is surfaced and polished, the process is comparitivley expensive, and the surfacing process leaves the plastics without any form of hard coating, so there is an additional process that may be supplied

In summary

If the filter is surfaced (not cast or rolled), has a tint applied, and then a hard coating and then a MAR coating, the process will be expensive, as it is time consuming, and each stage has reject rates

If the filter is cast, and the tint is added to the substrate before casting, the process is cheap and cheerful, and so is the filter

___

Glass: there are 2 sorts of tint: dye added t the molten glass / the glass is surface coated

the surface coatings on glass are tougher then the ones on plastics, but it is a relativity costly process. If the filter is incorporated in the glass, the result is very predictable, and the density of the filter changes with the thickness of the glass or the amount of dye used. Again the glass can be sent for MAR coatings to be applied
 
Richard King said:
its about pigment control. A plastic ND filter is made with a dip process - the blank is dipped in dye, that is hot for a determined amount of time. Getting the correct transmission, with no colour cast is very difficult. To top that, as the filter absorbs the dye, the solution has less dye in it, and the next filter takes the dye up at a different rate

If a surface coating is used, then if scratched, you have no filter where the scratch is

If the filter is then sent for a MAR coating, the coating process has a reject rate

If the filter is "cast" or pressed, the reject rate is high too, as surface blemishes are very hard to control. If the filter is surfaced and polished, the process is comparitivley expensive, and the surfacing process leaves the plastics without any form of hard coating, so there is an additional process that may be supplied

In summary

If the filter is surfaced (not cast or rolled), has a tint applied, and then a hard coating and then a MAR coating, the process will be expensive, as it is time consuming, and each stage has reject rates

If the filter is cast, and the tint is added to the substrate before casting, the process is cheap and cheerful, and so is the filter

___

Glass: there are 2 sorts of tint: dye added t the molten glass / the glass is surface coated

the surface coatings on glass are tougher then the ones on plastics, but it is a relativity costly process. If the filter is incorporated in the glass, the result is very predictable, and the density of the filter changes with the thickness of the glass or the amount of dye used. Again the glass can be sent for MAR coatings to be applied
Click to expand...

bah! i was just going to say that!
 
Richard King said:
its about pigment control. A plastic ND filter is made with a dip process - the blank is dipped in dye, that is hot for a determined amount of time. Getting the correct transmission, with no colour cast is very difficult. To top that, as the filter absorbs the dye, the solution has less dye in it, and the next filter takes the dye up at a different rate

If a surface coating is used, then if scratched, you have no filter where the scratch is

If the filter is then sent for a MAR coating, the coating process has a reject rate

If the filter is "cast" or pressed, the reject rate is high too, as surface blemishes are very hard to control. If the filter is surfaced and polished, the process is comparitivley expensive, and the surfacing process leaves the plastics without any form of hard coating, so there is an additional process that may be supplied

In summary

If the filter is surfaced (not cast or rolled), has a tint applied, and then a hard coating and then a MAR coating, the process will be expensive, as it is time consuming, and each stage has reject rates

If the filter is cast, and the tint is added to the substrate before casting, the process is cheap and cheerful, and so is the filter

___

Glass: there are 2 sorts of tint: dye added t the molten glass / the glass is surface coated

the surface coatings on glass are tougher then the ones on plastics, but it is a relativity costly process. If the filter is incorporated in the glass, the result is very predictable, and the density of the filter changes with the thickness of the glass or the amount of dye used. Again the glass can be sent for MAR coatings to be applied
Click to expand...

Now that, is an answer!!
 
Robbo said:
I know but one I looked at was £130 ....... even a 77mm B+W 10 stop is only 80.

Didnt know if they are harder to make for some reason
Click to expand...

Which ones were you looking at that cost that much?


towershot said:
Some are glass and so much more expensive,mine are plastic,and I have a scratch on one already.........:'(
Click to expand...

Would you mind point me to where I can find GND that are made of glass? Presuming you're talking of the none-circular / screw-on type :shrug:
 
Welding glass is cheaper :lol::lol:
 
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