Old 05-07-2007, 06:51 PM   #1
conrail_8123
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Hello All,


I am new in the digtal world and I have some questions about taking digital photos. I am using a Cannon Digital Rebel XT with a 28mm to 105 mm lens.

I am wondering if someone would be able to suggest what are good eposures for sunny and cloudy weather. I am guessing that iso 100 or iso 200 would be used for sunny weather and iso 400 on cloudy days. But what would be a good enough exposure that they will accept my photos. I have been using iso 200 @ F8 1/500 for my pictures.


Also can someone explain to me what soft means in the digtal world? Most of my pictures are rejected for being soft.

Can someone also tell me why the attached photo was rejected for being dirty. Maybe my eyesight is going. The picture looks fiine to me.


Thank you in advance for your help.

Chris
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Old 05-07-2007, 07:20 PM   #2
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On sunny days, my setting are generally around the "Sunny 16" rule. F16 & a shutter speed that matches your ISO (usually 200 for both). It's an old habit from my film days & I find it's still practical with digital.

Soft means your images are lacking clarity.

Your image is dirty because of the big dust spot in the sky. You probably have dust on your sensor...I'd recommend a blower of some sort.

Good luck...
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Old 05-07-2007, 07:42 PM   #3
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The smudge above the second unit is dust on the sensor. Do not blow on it or use dust off. Either use a digital sensor cleaning swab, or hold the unit with the sensor facing down and use a squeeze bulb to gently blow on it. Otherwise take it to a dealer and have them clean it for you.

Then try not to change lenses outside if you can help it.

Your pictures are soft because you are probably not using the sharpen tool in your photo software. Digital is different from film and because of the way the pixels and sensor filters work, all images require some sharpening. Cannon uses a sensor filter that requires a bit more sharpening than Nikon's do, but the result is the same once you have sharpened your image.

If you have some version of PhotoShop, your best bet is to use UnSharp Mask (USM) a term that sounds confusing, but is actually the best way to sharpen a photo. There have been a number of discussions in the forums and we all use different levels of sharpening. You will need to use a radius of between 0.5 and 1.5 and a percentage level between 70% and as high as 200% with a threshold of zero. Watch for "grain" or noise to appear and watch for a white border to appear around objects. When this happens, back off until the shot looks good. Do this as the last step in your image processing and do it with the screen showing the image at 100%.

Good luck.

Michael Allen
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Old 05-08-2007, 03:40 AM   #4
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Hi Chris,

In the attached image you should be able to see the difference a little bit of Unsharp Mask makes. I also cloned out the dust spot, most image editing software packages will have these features have a hunt around for them. If you follow Michael's advise your acceptance rate should improve just don't fall into the trap of over doing the unsharp mask.

Cheers,

Christine.
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Old 05-08-2007, 08:07 PM   #5
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Thank you for your help so far. I looked around and the photo software I have is ARCsoft Photo studio 5.5. I can not seem to find anything to do with the UnSharp Mask (USM). I did however find out how to clone things. Perhaps it is called something else or maybe I just don't have it. I did clean the sensor with a squeze bulb. I hope that will clear up my dust spot.

Thanks again,

Chris
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Old 05-08-2007, 08:16 PM   #6
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Quote:
I have is ARCsoft Photo studio 5.5. I can not seem to find anything to do with the UnSharp Mask (USM).
I don't have a copy in front of me, but look across the top for Enhancements. It should be listed under 'Sharpening Filters' or something like that, but definitely look under the Enhancements. That should narrow it down for you...

EDIT: If you don't find it, I'll update the info when I get home and look at Photo Studio...
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Old 05-08-2007, 10:39 PM   #7
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I was mostly correct. Using PhotoStudio, go Enhance->Sharpen Filters->Unsharp Mask.

The USM feature and parameters are a little different in PhotoStudio comapred to Photoshop, but when I used the program, I would set the Square Size to either 2 or 3, Effect 100, and Threshold 0 for the full size image. When I would size it down to 1024 pixels, I'd put the effect somewhere between 30 and 50 to see what it gave me.

Hope that helps...
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Old 05-08-2007, 11:10 PM   #8
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Quote:
Originally Posted by Ween
The USM feature and parameters are a little different in PhotoStudio comapred to Photoshop, but when I used the program, I would set the Square Size to either 2 or 3, Effect 100, and Threshold 0 for the full size image. When I would size it down to 1024 pixels, I'd put the effect somewhere between 30 and 50 to see what it gave me.
Chris, you may have confused a bit here by referencing two different file sizes - well, at least you did for me, were I the one wanting advice!

I have found it common advice to sharpen as the last step, and in particular do it after you have resized (to 1024x or whatever) so that you can see the effect, as that effect will vary depending on the number of pixels in the file. So I personally never sharpen a full-sized file (one not downsized for the web) prior to resizing.

If I am printing, and so saving a file that I have not resized, I will zoom the image until its size on the screen is the same as when it will be printed, and sharpen appropriately.

BTW, another reason to sharpen last is to make sure you sharpen after any noise reduction, so that you don't end up sharpening the noise and making it harder to subsequently eliminate.
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Old 05-09-2007, 04:44 AM   #9
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I always sharpen the full-size image (usually 125%, 0.5, 0) then the web-sized one (50%, 0.3-0.5, 0) as a last step. That's how I learned to sharpen and it's worked fine so far, and if you think about, technically I am sharpening as the last step!

And, I rarely, rarely do any noise reduction. The only time I do is on the occasional B&W shots where the noise shows up in the sky when converting to B&W. But I took a shot last night at ISO 800 (crazy, I know) that had little if any noticable noise.

BTW, Alan Crotty, Christine (the PS guru!), John West and Michael Allen all do the sharpen-resize-sharpen technique. See this thread:
http://www.railpictures.net/forums/s...ead.php?t=4522
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Old 05-09-2007, 12:32 PM   #10
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Interesting!

Actually, now that I look back at it, I also do some sharpening at the very beginning, in raw conversion. So count me in the club! Although I had forgotten; I had messed with it a bit two years ago and not revisited the choice since; it just defaults to a 25.

I shoot regularly at ISO 800 (I like the higher shutter speed when handheld) so I am used to seeing a bit of noise from time to time.
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