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Moire Patterns?
Old 12-19-2004, 03:25 PM   #1 (permalink)
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All,

Sorry this is going to long. This post will be a test of your patience with a newbie that is just starting to take pictures with a decent camera. [img]/ubbthreads/images/graemlins/smile.gif[/img]

I received my Canon EOS Digital Rebel two days ago. Prior to that, I had never played with things like White Balance, F-stop, shutter speed, etc. I am reading eveything I can, but I definitely have a lot to learn.

That being said ... I took the camera to church today because I was asked to take some pictures of a children's event in our Chapel. I have the standard EOS kit which means I have the 18-55mm lens and the built-in flash. I went in early to take some test shots and the Auto Everything shots looked bad in the lighting, I could not find an exposure and white balance that looked right, and using the flash made everyone's face look very white and washed out (told you I was a newbie).

I finally did a custom whte balance (without flash) and was able to get pretty even color across the pictures. They looked good on the LCD display. I took a bunch of pictures and when I got home to look at them in Photoshop, they looked a lot darker on the PC screen. I then applied the Photoshop CS Shadow/Highlight option and it created major moire patterns across the their clothes and background. I tried using a simple level adjustment to brighten them up, but they were still dark, so I had to use the levels and the hightlights (resulting in moire). Luckily, once I shrunk them down for the church's web site, they don't show the moire patterns.

With all this in mind ..... Here are my questions if you have the time:

1) What causes moire patterns and is there anything I can do to prevent it up front? The shots were taken with no flash using a custom white balance, an ISO of 1600 (I took some test shots at 800, but the movement of the kids caused a blur so I turned it to the highest setting allowed), f/4.5 and shutter speed set at 1/40 sec.

2) Is it normal for the picture to look brighter on the LCD that it acutally looks on the PC? If so, should I adjust on the camera until it looks brighter than needed?

3) Is it normal for the flash to casue the background to look good and the faces to looked white and washed out when the WB is set to indoor lights? Is that a camera setting I messed up (f/stop, shutter, etc.)?

4) Could the picture quality setting have anything to do with the above? I shot the pictures at JPG Large, but not at the "finest" setting.

Thanks again for your help! We are heading out of town in the morning for the Christmas holiday, and I plan to take a bunch of pictures on the trip. I hope to play with the camera some more this afternoon to try to answer some of these questions on my own, but packing the car will limit that time.

Earl
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Re: Moire Patterns?
Old 12-19-2004, 04:10 PM   #2 (permalink)
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[ QUOTE ]
I went in early to take some test shots and the Auto Everything shots looked bad in the lighting, I could not find an exposure and white balance that looked right, and using the flash made everyone's face look very white and washed out (told you I was a newbie).

[/ QUOTE ]

You must must must buy an external flash if you don't have one! It must be a flash with pan/tilt bounce capabilities, either a 420EX, a 550EX, or a 580EX! I have spoken!

Well, unless you're broke, like me. Then it's okay if you save up as best you can and buy one as soon as you can.

[ QUOTE ]
1) What causes moire patterns and is there anything I can do to prevent it up front? The shots were taken with no flash using a custom white balance, an ISO of 1600 (I took some test shots at 800, but the movement of the kids caused a blur so I turned it to the highest setting allowed), f/4.5 and shutter speed set at 1/40 sec.


[/ QUOTE ]

The usual suspect for moire patterns is compression. You were shooting at a medium to high compression setting at a high ISO which would have been very noisy which means it has to compress even harder. Other things can cause them but I think we've found our perp.

[ QUOTE ]
2) Is it normal for the picture to look brighter on the LCD that it acutally looks on the PC? If so, should I adjust on the camera until it looks brighter than needed?

[/ QUOTE ]

Yes, it is, and yes, it's very, very annoying. If you try to match it you will just get an unusable LCD display. The histogram is your friend. If you're reviewing a shot you should be looking at the histogram.

[ QUOTE ]
3) Is it normal for the flash to casue the background to look good and the faces to looked white and washed out when the WB is set to indoor lights? Is that a camera setting I messed up (f/stop, shutter, etc.)?

[/ QUOTE ]

It has nothing to do with the white balance. The faces are overexposed because they're a) closer to the flash and b) probably more reflective than the background. The typical solution to this is to drag the shutter but that does not work for action shots, obviously. There are just some shots where you have to decide which thing is going to be lighted properly and the rest is going to be off. There's no help for it, especially with a non-bounce flash.

[ QUOTE ]
4) Could the picture quality setting have anything to do with the above? I shot the pictures at JPG Large, but not at the "finest" setting.


[/ QUOTE ]

Yes. Also, the graininess inherent in shooting at ISO1600 will confuse Photoshop when you try to run certain correction filters.

The Digital Rebel is a good camera but it has all the limitations of any other camera plus some of its own. You'll get the hang of it.

M
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Re: Moire Patterns?
Old 12-19-2004, 04:21 PM   #3 (permalink)
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M,

Thank you! Thank you! Thank you! It makes sense now. Just more things to add to the list of what I need to understand with the new camera.

As far as the flash goes ... YES that is the next thing on my wish list. Christmas expenses (including this camera) has put the funds in a bind for a while.

Thanks again!

Earl
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Re: Moire Patterns?
Old 12-19-2004, 04:40 PM   #4 (permalink)
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You are welcome.

You wanna see noisy compression, try putting in the hack and shooting at ISO3200. [img]/ubbthreads/images/graemlins/smile.gif[/img] It *does* work, but it's... a bit grainy. Just a bit.

M
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