NatureScapes.net Forums

Intending to take some shots of the sunset behind the GG Bridge from Treasure Island, I attached two Singh Ray Galen Rowell DNG filters to the Canon 400/5.6 and got some serious ghosting. I had this happen before with shorter lenses (100 and 135), but not as extreme, and when taking off one of the filters it was gone. With the 400 even a single filter produced very strong ghosting.

I am wondering if this is a known phenomenon with these filters or perhaps the camera (Sony a7II), since I don't remember this happening with this lens/filter combo and any other camera, film or digital.

No this is not something that should be happening. First, are you using the lens hood? You should especially if there is any light source (sun bright light) that could be hitting the front element but isn't in the shot. Second, are the filters clean? Third, are the filters properly placed, there should be absolutely no light hitting the backside of the filters and allowed to bounce onto the lens. Are these screw on filters or slide into a filter holder type filters?

Hey Jens

I have had something similar happen when shooting infrared, where it is really apparent, as compared to normal shooting. What caused it for me was the light bouncing off one filter and reflecting onto the back of the other and back into the camera. Anti-reflective coating should normally take care of this, but I'm sure your filters are coated. Maybe try a stronger single filter, instead of stacking two, if possible.Could you post an image to show what you are seeing?

Did you mean GND?I have not heard of DNGs.

Joe

Hi Jens,
I would agree with EJ, these long telephotos seem to be very susceptible to flare when filters are added to the front element.
Both the Nikon 300mm f2.8 and the 600mm f4 I have feature a special curved meniscus non refractive front element (acting like a traditional UV filter) on them to protect the first refractive element. A flat one would presumably cause reflections and flare.
They have have a filter drawer at the rear of the lens to add effects filters.

EJ also stresses the need for the use of the lens hood. I agree - use it on ALL occasions! Even when not shooting directly into the light. It will dramatically improve the contrast of your images.

John Sibley

Thanks everybody for your responses. I just tried to repeat the ghosting effect by taking some shots with the same filter setup and pointing near the setting sun, but it didn't happen. Which makes the experience I had at Treasure Island even more mysterious.

I think it is caused by reflections on the filter surface. Preventing stray light to reach those filters would be a good practice, the lens hood is not an option, though. These are slide filters with a Cokin holder that is attached to the lens via a screwed-on adapter. I do have an accordion style hood that attaches to the holder, but it will leave the filters exposed to stray light. I will keep a black cloth handy to hang over the filters in case the phenomenon occurs again.

Thanks again.

If any light is hitting the back of slide on filters and the filter holder doesn't provide a complete seal of the backside of the filter you will get ghosting. that's why the Lee filter holders have a light sealing rubber backside. Many filter holders do not so it is imperative on those that the backside is shielded from any light at time of exposure - even wearing light colored shirts is enough to cause that. Some sort of shroud would be advisable or switch to a Lee or Wine Country filter holder.

John, you mention a meniscus front element possibly reducing flare. What I have found in shooting IR with an aspherical(4 asph elements) lens, although very different (but still non-flat), is that the flare is rendered as doughnut circles with the filters. I don't know how that would work in a non-IR capture, but it is very obvious in certain IR situations. I don't know if a meniscus lens would work similarly, but anyway I guess the point is moot on the large lenses you mention, since it is unlikely that anyone would be using front mounted filters of that size.

Joe

Here's a link to an article on the Wine Country filter system:

https://luminous-landscape.com/wine-cou ... em-review/

Joe