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Pentard !pjwjmEQ1RM
Photo question for the PRO PHOTOGS in the house.

I was shooting a model wearing some messenger bags in the alley behind my office yesterday and I got this really fugly moire effect on some of the bags.

Does anybody know what causes this kind of thing, and how can I avoid it in the future? It wasn't on all the bags, just this specific design...
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Camera-Specific Properties:Equipment MakePENTAX CorporationCamera ModelPENTAX K10DCamera SoftwareAdobe Photoshop CS3 MacintoshSensing MethodOne-Chip Color AreaFocal Length (35mm Equiv)60 mmImage-Specific Properties:Pixel CompositionUnknownImage OrientationTop, Left-HandHorizontal Resolution72 dpiVertical Resolution72 dpiImage Created2008:06:27 12:08:34Exposure Time1/350 secF-Numberf/4.5Exposure ProgramAperture PriorityISO Speed Rating100Exposure Bias0 EVMetering ModeSpotFlashNo FlashFocal Length40.00 mmColor Space InformationsRGBImage Width1024Image Height646RenderingNormalExposure ModeAutoWhite BalanceManualScene Capture TypeStandardContrastNormalSaturationHighSharpnessHardSubject Distance RangeClose View
>> Anonymous
Bayer interpolation artifacts maybe? If you shot RAW you might be able to fix it if you switch to a different interpolation algorithm.
>> Pentard !pjwjmEQ1RM
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>>213745

Interesting hypothesis!
I used to always shoot in JPEG since I'm an idiot, but switched to RAW 3 or 4 weeks ago after seeing how bad /p/ will RAGE when folks talk about shooting not-in-RAW.

Here's a different shot of the same design on a smaller bag, without the weird pattern. This one was shot in the shade, though, which I think is why the fabric didn't freak the camera out.

Camera-Specific Properties:Equipment MakePENTAX CorporationCamera ModelPENTAX K10DCamera SoftwareAdobe Photoshop CS3 MacintoshSensing MethodOne-Chip Color AreaFocal Length (35mm Equiv)64 mmImage-Specific Properties:Pixel CompositionUnknownImage OrientationTop, Left-HandHorizontal Resolution72 dpiVertical Resolution72 dpiImage Created2008:06:27 12:10:18Exposure Time1/90 secF-Numberf/5.6Exposure ProgramNormal ProgramISO Speed Rating100Exposure Bias0 EVMetering ModeSpotFlashNo FlashFocal Length43.00 mmColor Space InformationsRGBImage Width931Image Height931RenderingNormalExposure ModeAutoWhite BalanceManualScene Capture TypeStandardContrastNormalSaturationHighSharpnessHardSubject Distance RangeClose View
>> Pentard !pjwjmEQ1RM
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Camera-Specific Properties:Equipment MakePENTAX CorporationCamera ModelPENTAX K10DCamera SoftwareAdobe Photoshop CS3 MacintoshSensing MethodOne-Chip Color AreaFocal Length (35mm Equiv)49 mmImage-Specific Properties:Pixel CompositionUnknownImage OrientationTop, Left-HandHorizontal Resolution72 dpiVertical Resolution72 dpiImage Created2008:06:27 12:12:51Exposure Time1/500 secF-Numberf/4.0Exposure ProgramAperture PriorityISO Speed Rating100Exposure Bias0 EVMetering ModeSpotFlashNo FlashFocal Length33.00 mmColor Space InformationsRGBImage Width1024Image Height1024RenderingNormalExposure ModeAutoWhite BalanceManualScene Capture TypeStandardContrastNormalSaturationHighSharpnessHardSubject Distance RangeClose View
>> Anonymous
>>213746
What's going on with the top of the T-Shirt there?
>> Pentard !pjwjmEQ1RM
>>213752

Shitty artifacting from over-editing I assume.
The light was really fucked up from all the smoke in the air (california wildfires) so I had to tweak the color balance a lot to get the orange out.

Thankfully these images all end up at around 275x275px for viewing on the web, so my ineptitude is normally masked.
>> Anonymous
>>213744
Does that style of bag have a bunch of fine lines on it? I mean, do you see that effect with your eyes too? If you don't I must say that's really weird.
/notaprophotog
>> Anonymous
You're not using a polarizer? Those can cause funky patterns depending on surfaces and whether you're catching some of it full-on and some of it with indirect lighting. Specular surfaces and all that.
>> Anonymous
I get a lot of moire as well when I'm reducing the size of a JPEG that has a large area of close lines, like in knit clothes or window blinds. In particularly, the moire occurs when I reduce my 12MP image to something small, like 800x533.

I can reduce the moire effect by reducing the size of the image in relatively small steps when I get close to the small size. Since I sometimes do this often, I've created a Photoshop action for myself. I suggest you do the same.

Here are my reductions.
1. Start with your natural image size (e.g. 4000x3000)
2. reduce to 2000x1500
3. reduce to 1800x...
4. reduce to 1600x...
...
reduce to 800x...

Note that in Photoshop's "change size" dialog box, you can enter in one of the dimensions, and it will fill in the other dimensions to proportion.
>> Anonymous
>>213748
this picture is too dark. There is no separation between the bag and the girl's jeans. Use fill flash.
>> Anonymous
Am I the only one not bothered by moire? I just mentally write it off, the same way people write off what focal plane shutters do to car tires.
>> Pentard !pjwjmEQ1RM
>>213772
The bag doesn't have lines. I think the problem is with the weave of the nylon fabric.

>>213773
I wasn't using a polarizer, but that's a good idea. If the problem is a result of reflections off the nylon bag then a CPL might cut down on that quite a bit.

>>213783
Yeah. I know. Dunno why she decided to wear black jeans, since blue jeans are always better for shots like this. I have an off-camera flash on order through Amazon, but the bastards in their shipping department have been sitting on the order for almost a month now. ;_;
>> Anonymous
Too much unsharp mask, fag.