Grad ND plate question

[jonnyhorizon]

i have a 300d
i was given a grad ND plate thats about 4"x6"
says its a .6ND
i hand held it in front of various lens with and without polarizers and it seems to do the job
i like the idea of moving it up and down to get just the right horizon line
is this thing meant to be hand held?
and tips on using it?
it seems to attract finger prints very quickly

...

[robertwgross]

is this thing meant to be hand held?


NO.

The common system is called the Cokin filter system (rectangular filter sheets). They come in three sizes, A, for small lenses, P, for many larger lenses, and XP, for only the very largest lenses.

You buy one filter holder, which screws onto the front of your lens. Then you can slide in one or two or three filters, such as graduated neutral density. Cokin offers dozens of weird color filters and such.

My Canon lenses tend to be in one of two (filter) sizes, 72 and 77mm. So, I have one adapter ring that fits the 72 to the Cokin P holder, and I have another adapter ring that fits the 77 to the same holder. Then I have a couple of filter sheets that slide in.

The best way to size this up is to find a good camera shop that has a Cokin display, and they will have all of the pieces and parts as I describe. Otherwise, you can find them in the magazine ad for B&H. It is easier when you see the parts in your own hands.

---Bob Gross---

[jonnyhorizon]

i had heard of those systems when i first got my camera and started to look at filters but have never seen one
seems like a good idea
i read that the polarizers on those type systems were inferior to the standard type
i have a good hoya polarizer on my 77mm 17-40l but it does not have threads on the outside edge to allow me to add a grad nd
whe i put the grad nd on first it is difficult to see the orientation (bad eyesight) after i add the polarizer
i usally have lots of light (at elevation) and love the polarizer effect
i need to do some more work with just the grad nd without the polarizer
may have to bag the whole set up and go the cogin set-up
related: have been playing with the photoshop plug-in nik-efex which has a grad nd simulator
work for some limited needs
also have combined two RAW exposure levels but never like what happens where the two layers meet (lots of tedious clean up)
the miranda DRI pro combiner also has limited use
looks like i need to be more patient in the field and get it right on the original
...

[robertwgross]

i read that the polarizers on those type systems were inferior to the standard type
...

OK, but I think you want to use a rectangular filter holder system like Cokin for graduated neutral density filters, and use a standard round circular polarizer for that function, and don't try to mix the two.


i have a good hoya polarizer on my 77mm 17-40l but it does not have threads on the outside edge to allow me to add a grad nd


I can't think of any time when I tried to use both together. I don't think I would buy a polarizer without threads on the front side.

---Bob Gross---

[Penguin_101_1]

I have one of those systems and they work great. I will post pics if you want.

[jonnyhorizon]

yes please
also, other than finger prints it appears the plate works ok hend held
can you adjust it vertically in the holder?
...

[Penguin_101_1]

http://images2.fotopic.net/?iid=y3w20u&outx=600&noresize=1&nostamp=1
http://images2.fotopic.net/?iid=y3w20c&outx=600&noresize=1&nostamp=1
http://images2.fotopic.net/?iid=y3w20q&outx=600&noresize=1&nostamp=1
http://images1.fotopic.net/?iid=y3w20r&outx=600&noresize=1&nostamp=1
http://images2.fotopic.net/?iid=y3w20t&outx=600&noresize=1&nostamp=1
http://images1.fotopic.net/?iid=y3w206&outx=600&noresize=1&nostamp=1

[robertwgross]

yes please
also, other than finger prints it appears the plate works ok hend held
can you adjust it vertically in the holder?
...
Yes, that is the whole purpose of a filter holder.

Mine has three sets of slots, so you can push a filter up or down, but I can't quite imagine using three filters at the same time.

John Shaw or somebody recommended to cut off the outer set of slots (so that the holder only does two). Note that John Shaw only shot full frame cameras and not typical DSLRs with a 1.6 factor. So his idea to avoid vignetting isn't quite so relevant to the typical DSLR case.

---Bob Gross---

[jonnyhorizon]

thanks guys
i assume the entire system screws onto the camera as a circular filter would
that is an issue for me for i was hoping to comtinue to use my circular hoya polarizer - i think it is superior to any of the others i use and it does not have external threads
the idea of combining filters is something i am unsure of
does the upper half of a grad ND plate have the same effect as a polarizer?
i have noticed that under exposing a raw file in CS has a nice levels like polarizer like effect - but combining images is not as quick as i would like
...j

[robertwgross]

The filter holder screws into the front of a lens or other filter, assuming that the other filter has front threads.

There is no upper or lower part of a Cokin filter. There is one darker half and one lighter half in the graduated neutral density filter. If you use it normally, the dark half is up and the light half is down (but it could be the other way around).

Neither half works like a polarizer.

---Bob Gross---