Green/purple hue on certain images but not on others.

[andy53]

<p>Hi <br /> I hope i address the right forum for this question. If not please accept my apologies.<br /> Some of my images are showing green on the centre portion and purple on the edge when i zoom in and use F6.4 or smaller but it clears on full zoom or no zoom at all and no problem on larger than F6 in any zoom level. Sent camera to Fuji for repair got it back after 5 weeks they stated to replace something on it but nothing changed and i don't know what else i could do. This is happening in every possible combination of setting / low ISO high/slow shutter, high ISO/fast shutter, auto, manual,pre set program. The only setting i can use is either no zoom or full zoom and large F stop. I tried it in bright sun and shade and in between with the same result.<br /> Thank you for your understanding and time.<br /> Andy Klamar</p>

<p> </p><div></div>

[Alan Marcus]

<p>There are 7 major lens defects called aberrations (Latin to go astray). One of these aberrations is called chromatic (Greek for color). This is an inability to make a lens that causes light rays of different colors to come to a focus at the same distance from the lens. What you are seeing is called Lateral Chromatic or Transverse Chromatic Aberration. This is seen as fringes of color at the edges of images. The blue image forms inward and the red image forms outward. <br>

<br>

Now a convex lens and a concave lens have exactly the opposite chromatic aberrations. For the camera lens we need the lens to be convex which is known as a positive lens. To correct, the camera lens is made using a strong positive sandwiched with a weak concave (negative) lens. The result is an array of lenses of different shaped surfaces made of different types of glass. The idea is to mitigate as much as possible the 7 aberrations that plague us. <br>

<br>

In the end we can’t totally correct out all the aberrations. The better lenses are very expensive. </p>

[andy53]

<p>Hi Alan<br>

Thank you for your very quick response.<br>

I anticipated your answer and but i was hoping for a different one, - mechanical defect and they missed it the first time so send it back....- or similar.<br>

Now i think i have to convince my wife/treasurer to let me replace this one.<br>

Thanks again for your help.<br>

Andy</p>

 

[paddler4]

<blockquote>

<p>mechanical defect and they missed it the first time so send it back....- or similar.</p>

</blockquote>

<p>Not necessarily. It is not necessarily a defect. Lenses are not perfect, and many will show chromatic aberration under some conditions, typically on a region of high contrast (like the edges of your birds against the snow). That's why software like Lightroom has functions to help correct it. </p>

<p>It has nothing to do with ISO, shutter speed, or settings like manual or auto. It will be influenced primarily by aperture and the nature of the scene. </p>

<p>To explore it, find a high-contrast edge that isn't moving, put the camera on aperture priority mode so that the shutter speed will automatically adjust when you change the aperture. Start wide open (the smallest number you can set) and progressively close the aperture down (larger numbers). </p>

<p> </p>

[lex_jenkins]

Lightroom, DxO and others make software to help

correct chromatic aberrations. These work well.

Don't give up on a lens until you've tried these

tools.

[q.g._de_bakker]

This green hue in the center, with normal colour around it as your sample shows, is not (!) one of the lens aberrations, not chromatic aberation.<br>I haven't the answer yet what it is (have to look again), but it looks more like a reflection issue. Haze.

[paddler4]

<blockquote>

<p>This green hue in the center, with normal colour around it as your sample shows, is not (!) one of the lens aberrations, not chromatic aberation.</p>

</blockquote>

<p>right you are. Sorry, I focused on the fringing issue and didn't pay attention to the green tint--didn't notice that it wasn't uniform. I have never seen anything like the green center, but I agree that this does not look like a lens aberration. Looks more like a problem with the sensor, the firmware, or the electronics.</p>

[Alan Marcus]

<p>Not surprised by the greenish expanses in the center. This is surly not an optical phenomenon. I term it “subject failure”. Calling this “SF” is likely not valid in the digital world, to me it is reminiscent of printing errors commonly seen when printing color negatives on automated high speed photofinishing printers. <br>

<br>

Anyway; This snow vista sports large mundane areas of white snow taken under overcast conditions. We commonly see snow reproduce with a bluish tint because some blue sky contributes illumination. While this is likely not the case, let me theorize:<br>

<br>

The camera software is pre-programed to compress the file. These are various algorithms that cast out and then restores data. Mundane expanses are prime models. The software, seeing pixel after pixel with the same value, inserts a footnote and then deletes. The viewing software is commanded to restore the missing pixels. It is easy to understand that the restoration is keying in data that is slightly erroneous. You would never notice if the expanses are large and mundane. <br>

<br>

Next assumed: During exposure, photosites on the imaging chip are bombarded by photon hits. This action causes a charge to accumulate. This charge will eventually be assigned a numerical value that describes intensity and hue. This is digitizing, we often count on our digits (fingers), thus the origin of the name.<br>

<br>

Photosites that receive excessive photon hits are in danger of becoming saturated. In this state, some of the charge leaks out and influences adjacent photosites. This action is called “blooming”. This act induces false information which is what I think is happening as snow is highly reflective thus an overexposure, thus “blooming” is the likely cause. </p>

[lex_jenkins]

<p>The central greenish discoloration might be flare from the snow. If it appeared in only some photos and not others taken the same day, it's almost certainly veiling flare. That's a "softer" type of flare than the distinctive edged ghosting flare artifacts that are shaped like the iris (determined by the number of diaphragm leaves) and lens elements. Veiling flare is often colorless and tends to reduce contrast, but in some cases it may be tinted.</p>

<p>EXIF data shows you're using a Fuji bridge camera with a zoom. The many complex lens elements could contribute to this type of flare.</p>

<p>Were you using any filters, including a protective filter or polarizer? I see very similar flare in some of my recent infrared photos taken on a bright overcast day during a snowfall. I use three stacked filters, including two stacked polarizers, so there's lots of surfaces for flare. Usually I can minimize ghosting flare by shading the lens. But veiling flare and odd coloration artifacts will still occur in some photos, particularly when the sky and ground were both white.</p>

<p>I'm attaching a resized version of your photo, with the color exaggerated to show the green center and magenta corners. This is very similar to the effects I saw last week in some of my own snow photos, using one or more polarizers.</p><div></div>

[andy53]

<p>Hi Everybody<br>

First, thanks for all the comments. Looks like i started a lively discussion with this issue. Just to add to the confusion here is a couple more example to try to narrow the possibilities. The original warranty will expire in 14 days. Just showed the issue to the sales person where i bought the camera, he agreed the camera has a flaw but couldn't go further advised me to contact Fuji / again../.<br>

Thank you for all.<br>

Andy Klamar</p>

[andy53]

<p>Hi Lex<br>

Thank you for your thoughts. No i wasn't using any filters or polarisers, On the last example i left the zoom on wide and only went from F/3.6 and shutter 1/2 to F/10.0 and 4.0 sec. <br>

Thank you for your time and comment.<br>

Andy Klamar</p><div></div>

[curt wiler]

<p>This definitely appears to be a sensor or electronics problem. If the warranty has that little time left, I would want to have a written record that there is still a problem. Maybe dated correspondence or emails will suffice, but a work order from the store would be better. Having said that, I will add that I got very good service from Fuji when they had problems with the S2 sensor and mine went bad after the warranty period. They replaced it without question. That support is one of the reasons I jumped into the XF system when the reviews started looking extremely good.</p>

[paddler4]

<p>Well, there are at least two hypotheses on the table. One is that it is a failure of the senor or electronics. The other is that it is a result of the particular image.</p>

<p>Seems to me that it should be easy to get more information relevant to these. Take shots of a number of plain white surfaces. Paper would even do. First take the meter reading as is, then put in -2 exposure compensation, and then finally +2 exposure compensation. See if you have the same pattern of purple and green.</p>

[q.g._de_bakker]

It's flare: enough light bouncing off and between lens elements and sensor to rival the image forming light.

[andy53]

<p>Thanks for all of you. The camera was sent back to the manufacturer, let them figure it out.<br>

Hope this time they will.<br>

Best regards.<br>

Andy Klamar </p>