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Technical question

Postby lostcoyote » Sun Oct 03, 2010 11:20 am

not sure whre to post this so i am posting it here:

technical question regarding digital cameras:
i get some pretty severe banding occuring in the sky in most of my images which point near the sun.
i am using a point and shoot canon sd870 and i am petty sure it's because it's just a cheap point and shoot. maybe it's because they are JPEGs???

i am including 4 images: the left side being the unprocessed image and the right side having the brightness reduced to exagerate the effect that i am getting.

Image Image

Image Image

Image Image

Image Image


since i am interested in stepping back into 35mm and maverick has recommended either a Canon 5d or 1d, does anyone see this effect in their SLR's?
i read a report that canon has issued a statement that banding can occur in their 5d model.... so before i go out and spend several thousand dollars on a good quality DSLR, i want to see if this effect occurs in other peoples cameras whether it be canon or nikon. thanks.



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Re: Technical question

Postby maverick » Sun Oct 03, 2010 12:32 pm

Hi Lostcoyote

I have been working with Canon DSLR's for several years, and the 1ds Mark 3 for
3, and have not had any issues with banding, but Nikon, Sony, and other companies
make good dslr"s too.
IMO, if you want to make large prints to sell, then yes, get a dslr, otherwise if you
only want to make small prints, and post them on forums, than no.
I believe you have gone beyond the limit of extractable information you can get from
your jpeg files which is a good reason to shoot in raw since your latitude in both your
shadows and highlights will be greatly expanded.
Also try shooting one shot for you highlights, and one for your shadows, then combining
the images, which will expand you dynamic range.
This works mostly with static subjects, and you must use a tripod for perfect alignment.
Also do not forget every time open a jpeg file it degrades the file unlike a raw or tiff
file, which is something to consider for archival purposes.
If you want, you can send me a file of one of the pic's, and I can see what the exactly the
issue is, let me know.
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Re: Technical question

Postby copeg » Sun Oct 03, 2010 1:00 pm

lostcoyote wrote:since i am interested in stepping back into 35mm and maverick has recommended either a Canon 5d or 1d, does anyone see this effect in their SLR's?


I've seen this effect in quite a few situations, both digital and film converted to digital. When contrast is boosted up high in areas of tight contrast, a low bit value is used (eg 8 bit), or images are highly compressed into jpegs (or a combination of those) banding can result. There are ways around it...shooting raw, don't push the contrast in area's where it shouldn't be pushed, use 16-bit or higher when processing photos. Better quality cameras and descent processing software give you more flexibility to use these options and deal with artifacts such as this.
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Re: Technical question

Postby lostcoyote » Sun Oct 03, 2010 4:40 pm

okay maverick, i will send you the "untouched" file as it came from the camera.
you can lower the brightness to exagerate the problem to see just what it is.
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Re: Technical question

Postby maverick » Sun Oct 03, 2010 4:42 pm

Send to: pa.perfectlightphotography@gmail.com
From looking at the photo's more closely the problem is that the photos are jpeg
which are 8 bit of info instead of 12 bit, and you have blown the highlights, which will be unretrievable since they have fallen outside of the levels which your software can retrieve
any info.
Your trying to compensate or extract info (get blue back into the sky) cannot be done
since the info does not exist (the color blue you would like was not recorded), and there
for are getting banding because you have pushing past your jpeg files upper tolerance
levels (you can only get some much juice from a lemon).
There are things that can be done in Photoshop, and softwares like Vivenza that may
help, but in the long run it requires some work, and degrades the quality of the file
which is another reason to use Raw, but I still would like to see the file.
Here is an article about Raw which will give you some understanding about the differences
and the advantages to using Raw over Jpeg.
http://luminous-landscape.com/tutorials ... iles.shtml
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Re: Technical question

Postby lostcoyote » Sun Oct 03, 2010 4:52 pm

copeg wrote:
I've seen this effect in quite a few situations, both digital and film converted to digital. When contrast is boosted up high in areas of tight contrast, a low bit value is used (eg 8 bit), or images are highly compressed into jpegs (or a combination of those) banding can result. There are ways around it...shooting raw, don't push the contrast in area's where it shouldn't be pushed, use 16-bit or higher when processing photos. Better quality cameras and descent processing software give you more flexibility to use these options and deal with artifacts such as this.


it might be a jpeg issue. i don't know yet. the problem can be seen in the unprocessed (photoshop post prossed) images i got directly out of the camera. all of the shots in question were angled towards the sun but i did shield the lens from direct sunlight to prevent flare.

upon research, i noted that canon has acknowledged this as a problem, tho it's a different kind of banding:
http://www.digitalcamerainfo.com/conten ... -19629.htm

anyway, since my lil camera won't do RAW, i'm stuck here.... which motivates me to get a better camera. i was spoiled with the quality i got from my 4x5. and abandoned it because of the weight issue... so i went to the other extreme and have been using a cheapie point and shoot. i guess i'll have to compromise... cuz these banding issues do bother me, even tho i never plan to sell my work including the 4x5's.

post edit:
here is what a friend of mine just told me in email - it makes sense:
"It is an interesting problem. I looked at all the pictures in photoshop. The primary problem is as the highlights are blown in the original they lose the dynamic range and when you try to recover by darkening you see this by the effect which is similar to posterizing. All my camera equipment would do similar. I usually underexpose and pull up the darker areas in photoshop if a small amount is needed. The shadow highlight adjustment in PS CS or the backlight adjustment in Elements can be useful. Some cameras , my Canon 40D SLR for instance have a highlight tone priority setting (enable or disable) which increases the dynamic range from the 18% gray to the bright highlights (with some caveats). If possible the best solution would be multiple shots bracketed and blended together with a program like photomatix. A quick look at samples on photomatix will illustrate"
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Re: Technical question

Postby maverick » Sun Oct 03, 2010 5:23 pm

Yes, this is what I was referring to when saying that you can take 1 photo for the
highlight, and 1 for the shadows combining them to get a wider dynamic range
and then use Photomatix Pro Fusion, which I use also, to combine them.
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Re: Technical question

Postby lostcoyote » Sun Oct 03, 2010 7:40 pm

okay, thank you guys for all of the feedback. i think i understand what is going on. has everything to do with quantization noise & compression artifacts. i'll have to employ the 2 exposure technique and see if that fixes the problem.

this topic is sorta disruptive to "high sierra photography" as it has nothing to do with the high sierra photography category per se.
so if you want to delete it, that's fine with me.
thanks again :)
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Re: Technical question

Postby ericZ » Tue Oct 19, 2010 2:45 pm

i hope it's not deleted, it's important information for those just getting (back) into photography.

it sounds like you're on the right track. if you've been around photography for awhile, it's like shooting with chrome film. expose for the highlights. the more things change, the more they stay the same...

the images you posted show the "original" files are overexposed (from what i see on my monitor). maverick's right about the lack of digital information. it's just not there. i typically shoot with a canon 5D, Mark II, Mark III and a 7D on a daily basis. and just added, a little optio W90. big difference in image quality. the trick for the W90 point and shoot is to set the exposure compensation to 1.3 stops under for most sky scenes. shooting RAW would help (i guess, i never do with my pro cams and not possible with my P&S) but i'd say it's not entirely necessary.

also, i think banding can happen when the file capture size is too small. or rather a bigger file size might help. try increasing the file capture size in your P&S. in the end, RAW helps with situations like what you showed and the newer cameras like the 5D Mark II will offer what you need to insure no banding will occur. it takes some time in post production (which is something i cannot afford when on deadline so working with 8 bit images is just fine) but may just be up your alley, so to speak.

eric
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