Moire...ugggggggggggggggggggg

[Mike Hollingshead]

Does anyone know any good tricks to correcting this issue either before hand or after the fact? It's driving me nuts and I'm getting really sick of seeing it. I'm starting to wonder what causes this more, the camera or the lens. The rebel or it's lens is terrible at this when shooting storms. It's not only in the strong contrast areas but many times just smeared across the clouds. Bluring seems to never work well without bluring your detail. I've tried to desaturate that exact color but that sometimes doesn't work well either(and it's a royal pain if many images have the problem). Thoughts?

 

[Jeff Lawson]

If it's a true moire pattern, it's probably the camera, but it's strange that it would be visible in non-detailed areas like clouds. Do you have an example?

 

[Mike Hollingshead]

[Broken External Image]:http://www.extremeinstability.com/stormpics/ex1.jpg

[Broken External Image]:http://www.extremeinstability.com/stormpics/ex2.jpg

Maybe it's not moire but just a lens issue(I am hoping). It's a pain in the butt if you try and make any decent sized prints.

 

[Jeff Lawson]

Strange. That does indeed look like a moire pattern, but why it shows up there, of all places, I don't quite understand. Were you using any filters?

From the thumbnail, I'm guessing the image has already been post-processed. Is that zoomed portion from the post-processed image or the original?

 

[Mike Hollingshead]

No I wasn't using any. This is actually pretty typical for storms I'm finding. It is post-processed. When I grabbed the larger part I did a quick auto-levels just to show it a little better(didn't enhance the problem too much more then what is in the thumbnail. I can get rid of it, but it's a pain and sort of tricky to do right(since my monitor sucks to begin with). It'd just be nice to know what to do to keep it from happening or what is the actuall cause. Also, see the st logo? The area where the sun is the strongest on the right had quite a bit of it in arcing lines(this is also common). Edges like the horizon also love chromatic aberations side effects(red line). Seems like every problem comes out when shooting storms and most other instance are fine, lol...fantastic.

 

[Aaron Kennedy]

Moire typcially *that I know of* shows up in fine patterns. Why it would be in clouds I don't know. Were you shooting through filters or glass? Can you see it in the original? IT is probably some other optical phenomana.

Aaron

 

[Mike Hollingshead]

No, I never shoot through glass(cept for the lens..for you smart people out there about to comment). It's typical. I bet it's a lens issue(that or I'm really hoping it is).

 

[Aaron Kennedy]

What lens?

 

[Mike Hollingshead]

The crappy kit lens, EF-s 18-55mm. Anyone else with the rebel notice this problem with storm photography?

 

[Jeff Lawson]

I have the 18-55 (and a 300D), but haven't used it for shooting storms. I've never noticed the problem myself in photos I have shot with it, but I don't use that particular lens much anymore, so I'm working with a small sample.

Chances are, it's some lens funkiness. I know you've mentioned problems with the lens before, so perhaps you have a bad copy. The 18-55 is indeed a finicky lens - I only use mine when I need the wide angle. Otherwise, the softness near the edges when wide open annoys the heck out of me.

 

[mark humpage]

Is it a true 35mm lens or 35mm lens designed for digital.

One of the problems you have highlighted comes with incompatibility with the sensor (new technology) and 35mm lenses (old technology). It would be interesting to get the Canon answer to this one.

To combat this and take the steer from Olympus, who were the first to design a FULLY compatible digital system (E1 camera and lenses), most other lens manufacturers are now jumping on the digi lens bandwagon.

Mark

 

[John Diel]

What ISO were you shooting at? This appears to be a typical High ISO noise pattern. The color shifts are due to the way the Sensor records the light patterns.

Digital "noise" is kind of like Film "grain". The higher the ISO rating, the more grain/noise you get. It shows up as color bands and shifts in the photo. Even on a good day and you mistakingly use a high ISO, the color shifts out like this. I've done portraits where I was supposed to shoot at ISO 100 and shot at ISO 800. The shifts were there and then disappeared when I got the proper ISO.

The 10D and the Rebel use the same sensor and algorythms so the ISO "noise" is similar. Try a product called "Noise Ninja" http://www.picturecode.com/. This is about the best product I've found for reducing the ISO noise. It also does a pretty fair job of cleaning up pictures on other counts as well.

Also, the image ghosting (Chromatic aberration) is due to the lens. Poor quality lens will do this consistently. Get a better lens and this should go away. I'm using a sigma lens (nothing special about it, standard 28-90mm) and haven't seen any issues (so far) with the magenta ghosting.

Mark wrote: One of the problems you have highlighted comes with incompatibility with the sensor (new technology) and 35mm lenses (old technology). It would be interesting to get the Canon answer to this one.
Mark,
I would like to know your source of information on that comment. Most of the compatibility issues I've heard of are electronic related, not due to a lens. There are great lenses, mediocre lenses and downright bad lenses, but a compatibility issue? I can't say I've heard of that one yet. Granted, sensor size makes a difference in the way the final image is projected on the sensor (resulting in the famed 1.4x - 1.6x magnification factors which are really crop factors). The glass itself should not make a difference on how colors are reproduced to the sensor.

Of course we all know this isn't true. There are factors in how the glass bends the light to the image plane and this sometimes results in color phasing (the magenta ghost on objects of high contrast, aka Chromatic Aberration) but with decent lens I haven't seen this issue on the 10D.

I might add here that I also use the Olympus E-1 and believe it puts to shame just about any other DSLR styled camera when it comes to portraits. As an action camera, it really doesn't work out. But for a landscape/portrait camera, it's still tops!

John Diel

 

[Mike Hollingshead]

Thanks for the thoughts/posts on this. I believe this was actually shot at ISO 100(as I have sworn off anything higher). I'll have to check when I'm back home but being it was an August chase I think by then I was pretty learned to stay the heck off anything over ISO 100(for storms or low contrast shots). I have had Neat Image for a couple years now and love it at times....though I've not taken the time to use it at it's fullest capabilities. I hope the color lines are due to the lens and not something I may of done to the camera. I have noticed the colors are sometimes really bad with this lens. I get alot of "yellow" where it should be closer to white(no, adjusting the white balance doesn't fix this).

As for the lens being designed for digital, it is the kit lens(EF-S that was made for digital I guess). I'm not sure that is the issue as most lenses being used on DSLR's are old "film" lenses.

I don't think it's a noise issue either though. You might be right there, but I've never heard of noise coming in patterns(but it's interesting noise is often in these very colors). A lens distortion issue seems like more of the culprit. Aaron can you mail me your new L glass to use for a bit? I promise I'll ship it right back.

 

[John Diel]

Mike,
You may be right on with the issue being the lens. I haven't paid much attention to the ED-S lens as my camera won't support it. I've shot lots of cloud shots and storm shots with the sigma and not had any issues at ISO 100 & 200. White balance would have been my next bet, but it sounds like you have that covered as well.

Next question: Are you shooting RAW or JPG? RAW is exactly what it says it is. It's the RAW information as the sensor sees the light. There is no in camera processing. White Balance is not applied, nor any sharpening routines. Any adjustments are made when the RAW information is converted using Canon's RAW Converter or a third party conversion (Photoshop CS has one built in and there are others). This creates a TIF file (Generally uncompressed, hence a large file).

To find out if it's the lens, try shooting a couple of shots of some with plany of colors over the spectrum. Shoot it in the various modes of the camera. If you know someone, get them to loan you a lens for the test.

If the same issues show up across the test shots AND between RAW and JPG, I woul say it's most likely the lens. If you are able to get a loaner, and the same thing happens, it's a more serious problem with the sensor or firmware.

Hope that helps!

John

 

[Carey Walton]

The pattern noise you are seeing is probably due to a number of reasons and the bottom line is that you are viewing the signal to noise ratio of your camera. This pattern noise appears to resemble a moire like pattern due to the layout of the pixels and their associated analog to digital converters, and is most visible in low contrast areas such as sky and clouds. Areas with lots of detail tend to mask the noise visually.

The pixels in a sensor are all very close in sensitivity, but they aren't perfect. Each pixel may output a a slightly different value relative to all receiving the same amount of light. Add to this the errors introduced by the analog to digital converter and the fact that the lower luminance levels occupy fewer steps on the histogram all add up to produce noise.

This accumulation of noise is further enhanced visually by increasing the contrast in post processing.

Unfortunately, storm photography involves scenes with very low contrast and high dynamic ranges, but there are couple of things that can be done to minimize the effects of noise.

1. Shoot to the right, and what this means is to use the histogram display on the camera to get the exposure towards the bright end of the scale. A very good article about this can be found at http://www.luminous-landscape.com/tutorial...ose-right.shtml.

2. In post processing, use of the curves and levels tools in Photoshop can make a big difference, but I'm still struggling with this one.

3. Sharpening further aggrevates the effect. Use minimal sharpening in the begining and try unsharp masking as the final step in processing. Careful selection of the threshold values along with the amount and radius can minimize the noise in flat areas while still sharpening the areas with detail and higher contrast.

Hope this helps!
Carey