nd400/nd110 banding problems

[night86mare]

hi guys,

i have mentioned this quite often, just throwing it up properly for discussion.

i remember emlee used a term once to describe this problem, but i cannot seem to find it anywhere, despite doing searches using google, clubsnap..

when i use nd400 or nd110, sometimes, just sometimes, there will be a horizontal strip across the image, some days it is really bad, some days it is not so bad, but the thing is, it seems entirely random. i can take a picture using a tripod, same exposure, same settings, it will appear in one picture, less in the other.

this is a page that i found when snooping around describing approximately the same problem:

link

image posted there

i am wondering what is causing this - whether it is a camera problem, since it shouldn't be the filter problem. if it is , i might consider getting pentax to look at my k20d.

anyways, i was googling around, there is something on photo.net here about the horizon 202, there is both dark banding and bright banding, but the problem i experience tends to be bright banding.

could this be TIR (total internal reflection problem) due to the extremity of the filter being used? after all, it is 9-10 stops, i am sure the optics wise will not be as easy to handle during manufacturing as compared to more normal nd2/nd4/nd8 filters.

thanks in advance for your replies.

 

[splim]

just thinking if light ever leaks in from viewfinder :think:

 

[monolime]

Could be stray light entering thru the viewfinder thus affecting the exposure. Perhaps can try covering the viewfinder.

Source: flickr ND110 group discussion.

 

[spheredome]

Don't know what is it but is there a change this only affects that Pentax model?

 

[romeo tango]

How often is the occurance ?

you might want to try this, just to confirm it is not light going thru' the VF :

1) take 10 shots of the same setting - see how many affected
2) take another 10 shots of the using the above setting, but this time cover the VF

See if the second set is ok. Just a suggestion

 

[night86mare]

just thinking if light ever leaks in from viewfinder :think:

Could be stray light entering thru the viewfinder thus affecting the exposure. Perhaps can try covering the viewfinder.

Source: flickr ND110 group discussion.

that would make sense. i will give it a try the next time i have an opportunity.

have any of the nd400 / nd110 users experienced this banding problem?

i wonder if it has anything to do with this VPN noise issue that i am seeing for k20d being discussed elsewhere.

 

[Lolrence]

I've never got that problem with my Canon camera... but I do get problems where sometimes, the metering will go haywire after taking the filter off (after I've took photos with the filter for long exposures)... It might be because of it being an old model (20d)...

I don't cover my viewfinder when taking long exposures (partly lazy ;p)... for your case, it looks like a reflection of sorts to me... I've not experienced it, so I can't comment much..

 

[night86mare]

that might be because of metering time issue, my camera can vary the time taken for metering, etc.. maybe your 20d is set to longer period of metering.

hrm. i wonder if it's a sensor issue.

in any case, i've lived with it so far, just wondering if it is just me who's experiencing this, or just k20d users, or more than a few people doing it.

lypklypk, you always use spirit level? for some funny reason, everytime the camera is level, there is no such issue, which leads me to think about the reflection thing again.

 

[Yapster]

lypklypk, you always use spirit level? for some funny reason, everytime the camera is level, there is no such issue, which leads me to think about the reflection thing again.

Hmm, not sure if this image of mine is due to banding or reflection from the sun/water.

This

My camera was aiming downwards at less than 45 degree with the ND400...

I am also looking for the reason.

So far, this is the only encounter i have. I don't have a spirit level though. :sweat:

Based on the link you gave, the user seems to be aiming downwards and he mentioned there were fairly strong side lighting.

It is most pronounced in vertical images but is also present in horizontal photos as well. I do not believe that there is a problem with the B+W filter, but thought one of your photography experts might know what is going on. There was fairly strong side-lighting and if I had been able to see these artifacts on my LCD, I would have tried to block some of that light. Any thoughts?

 

[Lolrence]

that might be because of metering time issue, my camera can vary the time taken for metering, etc.. maybe your 20d is set to longer period of metering.

hrm. i wonder if it's a sensor issue.

in any case, i've lived with it so far, just wondering if it is just me who's experiencing this, or just k20d users, or more than a few people doing it.

lypklypk, you always use spirit level? for some funny reason, everytime the camera is level, there is no such issue, which leads me to think about the reflection thing again.

I gotta get the nick changed, I hate it now :bsmilie: Just call me by name lol. You should know it already

I don't use a spirit level at all... I've even shot into the sun (never really had light shining in from an angle though), and I don't get reflections (I really do suspect they are) like that in my photos... Do a test, shine a light while taking a long exposure and see whether you get the same thing happening to your photos.

As for my cam, I think it's the cam going haywire lol.... the metering goes off for quite a time, I've to turn on and off the cam many times and let it rest for a while (off by 3-5 stops, can't remember... shooting in bright daylight at f5.6 gets me a non hand-holdable shutter speed lol)

 

[catchlights]

I don't have the ND110, and didn't use ND400 to shoot at f22, so have not experience this

light enter from viewfinder will affect the metering, but will not affect the exposure, do remember the mirror will be filp up to cover up the focusing screen before the shutter open, and it will be holding up till the shutter closed and return to normal position.

one possible explanation is the chamber itself are not dark enough, certain part reflex light more, or another possible thing is the seal of mirror is not light tight, so it has light leak when it is in up position.

 

[night86mare]

yapster:

yeah, i think mine only seems to happen when i aim downwards. after all, for landscapes, not much point in aiming upwards. lighting also tends to be side, from memory.

i am thinking it is reflection, in part because at vietnam area, i got a few pictures where it happened a lot more, like just happy vertical overexposed strips all over the picture. i am thinking this is probably because of wave moment and sun position and some sort of total internal reflection, based on that.

since you seem to be getting it as well, at least i'm relieved that it isn't a camera or sensor problem. what are the chances that both cameras are problematic?


terence - yes, maybe i'll try it tonight, the torchlight thing. (hope i didn't get the name wrong)

uncle catchlights - yes, i thought so too. ir people mention the same thing before for viewfinder only affecting metering..



i am looking at photos of "light leaks", it doesn't seem quite the same... hrm

 

[Yapster]

yapster:

yeah, i think mine only seems to happen when i aim downwards. after all, for landscapes, not much point in aiming upwards. lighting also tends to be side, from memory.

i am thinking it is reflection, in part because at vietnam area, i got a few pictures where it happened a lot more, like just happy vertical overexposed strips all over the picture. i am thinking this is probably because of wave moment and sun position and some sort of total internal reflection, based on that.

since you seem to be getting it as well, at least i'm relieved that it isn't a camera or sensor problem. what are the chances that both cameras are problematic?

Ya, maybe it is how the lights reflect internally when we tilt the lens downwards.

Here's another shot where i didn't tilt the cam (was on lower ground with wide angle), the light was strong too, but no such banding.

This

Another possibility i can think of is the ND filter is not convex while our WA front element is. This, since the 2 pcs of optics are not hmm, parallel (?), when we tilt the lens, the stray lights may reflect/refract from the corner. Thus the banding. Haha, i not lens engineer, i also :dunno:.

Ya, don't think it is the camera ba.

 

[Lolrence]

Lol it's Lawrence...

Yea, test it out and let us know... I'm quite sure it's to do with reflection/refraction occuring...

 

[billycadiz]

:thumbsup:
TFS guys!!!