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Author Topic: What is wrong with this image ?  (Read 993 times)

jeremyrh

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What is wrong with this image ?
« on: April 29, 2019, 07:49:50 am »

OK - I know that from a technical and aesthetic perspective there is a list of things that are wrong, but what I am specifically looking at is the dark strip covering approximately the left hand quarter of the image. A few other images from this outing show a similar stripe, but not all of the same width. It was shot with a Nikon Z7, 24-70 f/4 and (I think this may be key ...) a ND grad (vertical, not horizontal!!) and a CPOL filter. The stripe is seen on the un-processed file in Capture One and also Nikon Capture (or whatever it's called these days!).

Any ideas what it might be, or tests to run?
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kers

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Re: What is wrong with this image ?
« Reply #1 on: April 29, 2019, 07:52:14 am »

just shoot wth and without the filters and see the difference...
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jeremyrh

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Re: What is wrong with this image ?
« Reply #2 on: April 29, 2019, 07:57:59 am »

just shoot wth and without the filters and see the difference...

Yeah - I did that back home shooting a plain wall and there was no stripe visible, so I was wondering about it being some weird thing to do with a combination of the light conditions and the filters.
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rabanito

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Re: What is wrong with this image ?
« Reply #3 on: April 29, 2019, 09:10:04 am »

Yeah - I did that back home shooting a plain wall and there was no stripe visible, so I was wondering about it being some weird thing to do with a combination of the light conditions and the filters.

I know you are interested only in that strip on the left but the whole picture has some "inexplicable" problems, such as the inhomogeneous colors on the sand bank and on the rocks
Or is it noise and the image is just part of a big enlargement of the original?
The sky looks also very uneven
Maybe all these effects are related?
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PeterAit

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Re: What is wrong with this image ?
« Reply #4 on: April 29, 2019, 09:16:44 am »

Sauron is coming!
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jeremyrh

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Re: What is wrong with this image ?
« Reply #5 on: April 29, 2019, 09:58:25 am »

I know you are interested only in that strip on the left but the whole picture has some "inexplicable" problems, such as the inhomogeneous colors on the sand bank and on the rocks
Or is it noise and the image is just part of a big enlargement of the original?
The sky looks also very uneven
Maybe all these effects are related?

For the colours I think there is some over-enthusiastic use of sliders. For the sky maybe that is the effect of the polariser.
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kers

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Re: What is wrong with this image ?
« Reply #6 on: April 29, 2019, 10:05:10 am »

What i noticed; polaroid filters with wide angle lenses always gives problems for the polarizer woks in one direction, resulting in uneven colors/densities across the frame.
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Slobodan Blagojevic

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Re: What is wrong with this image ?
« Reply #7 on: April 29, 2019, 10:13:59 am »

Missing info:

- focal length (24?)
- aperture (f/16-22 range?)
- type of GND filter (hard?)

If my assumptions above are correct, the stripe is actually the GND filter.

jeremyrh

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Re: What is wrong with this image ?
« Reply #8 on: April 29, 2019, 12:27:41 pm »

Hi Slobodan

The GND was 3 stop medium. F8 and about 30mm focal length. The GND had the dark bit at the top :-). I am trying to concoct some sort of explanation in terms of the very low and directional light interacting somehow with the vertical edge of the filter but it makes no sense. Of course using a new camera I immediately thought "OMG MY SENSOR IS HOSED"  but that doesn't fit the observation that different pics have different width stripes
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Dave (Isle of Skye)

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Re: What is wrong with this image ?
« Reply #9 on: April 29, 2019, 01:34:58 pm »

Have you tried setting your kit up in exactly the same way and then taking a shot of a blank surface such as a wall? If the fault is there again, then it is something in the camera or GND, if not, then it was something to do with the direction of light and how it was passing through lens or your GND.

It could also be just a natural phenomenon of the lower light reflections from under the cloud layer on the left, even though it looks like a straight line of darker pixels, reflections can sometimes do this kind of weird thing.

But as I say, if you can replicate under controlled conditions, then something is a amiss with your kit, if you can't then it was just the light on that particular day or something.

Dave
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jeremyrh

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Re: What is wrong with this image ?
« Reply #10 on: April 29, 2019, 01:43:11 pm »

Hi Dave

Yes - I tried to reproduce the "fault" by shooting a blank wall with the same camera setup, and did not see any "stripes" so I think you are right - it's "one of those things". On the next frame to the one I posted, with very similar composition, there is a stripe about half the width of the one you saw, suggesting it's light-related and not, say, a sensor problem.
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KMRennie

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Re: What is wrong with this image ?
« Reply #11 on: April 29, 2019, 05:37:12 pm »

Very difficult to say when you post such a small image with all of the exif data stripped from it. Looking at this image you have more colour noise than I have ever seen on an image, even from an old phone. Blacks are blocked and highlights are blown. What ISO were you using, I suspect very high? I don't understand your comment about the orientation of the nd grad. As others have written try setting your camera to ISO 64, remove all filters, sun over the left shouder and shoot a series of "easy" landscapes with the histogram not quite hitting the right hand edge. If the resulting image looks like this then return the camera. Ken
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Slobodan Blagojevic

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Re: What is wrong with this image ?
« Reply #12 on: April 29, 2019, 06:22:53 pm »

... I am trying to concoct some sort of explanation in terms of the very low and directional light interacting somehow with the vertical edge of the filter but it makes no sense...

Hi Jeremy,

It actually makes a lot sense. Back in the day when I was fiddling with GND filters (ancient history) I remember some filter-holder manufacturers had a contraption that used to cover the top of filters to block any stray light. I speak from memory, so it may not be a contraption, but just an advice. In any case, it makes sense, given that GND filters are rather thick pieces of plastic. I used to cover the top by a little piece of lens-cleaning cloth.

John R

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Re: What is wrong with this image ?
« Reply #13 on: April 29, 2019, 07:05:57 pm »

I had an issue with images turning green and then purple, depending on how the filters were turned. It turned out to be the use of two filters from two different brands. One was polarizer, the other 8x neutral density filter. I would show you, but I think I have since deleted them. To Slobodan's point, not only may he be right but if I am not mistaken the issue of stray light with square and rectangular filters that sit on holders, is well known. Some brands make a big deal about it and make a point to indicate that their filter system has dealt with the issue. I found a link to that illustrates what we are discussing and resolves the issue by creating a filter frame to cover the edges of the filter.

JR

https://www.youtube.com/watch?v=jMVPuc4N0V4

https://www.barkerphotographic.ie/benro-100-x-100mm-filter-protecting-frame-fr1010/camera-accessories/filters
« Last Edit: April 29, 2019, 07:24:38 pm by John R »
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KMRennie

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Re: What is wrong with this image ?
« Reply #14 on: April 30, 2019, 05:56:17 am »

Hi Jeremy I am another of the dinosaurs that still use ND grads. I tried to replicate your effect and although not identical it is close enough to make me think that they have a common cause. I used a 10 stop ND filter and din't put it in the rear slot, this will allow light to leak around the edges, I used a sunset grad with a darker band and it can be seen, I also used a polariser. I also allowed the sun to strike the edges and full onto the filters, I also allowed light in through the eyepiece not a problem with the Z7. Your image had incredible noise and I replicated it by increasing the ISO to 25,600 the max on my D810 but your Z7 goes a few stops higher. This lot gives an exposure of 1/20s @f6.3 looking at the waves in your image this would seem to be in the correct ballpark. This lot gives the first image(DSC7093). I then swopped the positions to put the ND at the correct rear slot and the grad in front and still allowed the sun to strike what it would and this gives the second image (DSC7094).
I have once produced results like this before when at Bamburgh I tried for the long exposure look and started to apply ever stronger ND filters without noticing that I had my camera set to auto ISO and the greater the filter factor applied the higher the camera pushed the ISO and I got a smudgy mess. I hope that this helps. Ken
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