I am new with ND filter. I bought two Cokin ND filter P154 (ND8) and P153 (ND4) recently. When I use them seperately the result is fine. However if put them together on the holder the result is quite different with red tone. I am not sure if I use them incorrectly or something else. I attached the resulted photos here. Any advice is highly appreciated.
Yi
https://www.cambridgeincolour.com/fo...achmentid=5562
#1 ND filter
https://www.cambridgeincolour.com/fo...achmentid=5559
#2 ND 4
https://www.cambridgeincolour.com/fo...achmentid=5560
#3 ND 8
https://www.cambridgeincolour.com/fo...achmentid=5561
#4 ND4+ND8