# Question on Cokin filters

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#### roygoh

##### Senior Member
Hi,

I have the Cokin filter with adapter rings to fit my 80-200mm and 24-50mm lenses, and am looking at getting Cokin's closeup filter (+2).

Thanks!

Roy

#### yellow_kiwi

##### New Member
wats ur type of cokin filter system? P?

#### roygoh

##### Senior Member
I currently own the following:

1. Adapter ring for 52mm dia
2. Adapter ring for 62mm dia
3. P.021 Blue (80B)
4. The filter holder itself

I believe this is a system "P", because the filter size is 83mm X 83mm.

The +3 closeup filter for P system is US\$15.95 from B&H. Would appreciate if you can provide some feedback on the following:

1. For a lens with minimum focus distance of 1.8m, what would be the focusing distance with a +3 close up lens added? Is there a simple formular for this calculation?

2. With the sliding holder system, how critical is the alignment of the optical centre of the cose-up lens with the optical axis of the camera lens?

3. How is the optical quality compared to standard ring-type close-up lenses? I guess the Cokin filter is most likely plastic instead of glass.

4. Can I stack 2 pieces of +3 filters on the filter holder? (ignoring further degradation to the image quality)

Thanks!

Roy

#### surge

##### Senior Member
i currently use both the cokin and screw on filters. for close up i prefer screw on since no adjustment is required as in a grad filter for the horizon.

you need a P filter system if you are referring to 80-200/2.8 due to the large 77 thread.

to calulate the distance from lens to subj., divide 1 meter by the close up factor-that is the further you can focus with the filter on at infinity

set lens to infinity

eg: if +1 close up means 100cm/1 you can focus at 1m.

if +2 then 100/2 or sharp focus at 50cm

thus a +3 would be sharp focus at about 33cm.

you can then focus nearere by shifting focus from infinity to minimum focus but range is usally about 5 inch max.

there is a more complicated formula but i think this is a good guide

#### roygoh

##### Senior Member
Thanks for the info.

I have confirmed that the system I now have is the "P" system.

My 80-200 is the old f/4.5 manual focus. The filter diameter is only 52mm.

I also have a 35-70 f/3.5 MF, which is 72mm. My only AF lens is the 24-50mm f/3.5-4.5, which has 62mm filter diameter.

Since I already have the basic Cokin kit, I would like to be able to share filters between the lenses. The filters that I am now interested are:

1. +3 close up (may get 2 if stacking is possible and gives acceptible results)

2. ND filter

- Roy

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