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Old Apr 10, 2003, 3:58 AM   #1
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Default Beware of 'sudden' dust at smaller apertures

I recently snapped a few dozen macro shots using my new 100mm macro lens, while on a field trip. I was quite pleased until I later noticed on the PC almost all images had a distinctive pattern of dark blotches. As it turns out it was dust on the sensor which wasn’t visible using larger apertures – I later checked some of my previous images with standard lenses and sure enough the dust was also there, but only visible after serious magnification under photoshop – not a real problem on those images. But, the macro pics were clearly a mess.

I would recommend that digital SLR users take a few test shots before embarking on any serious macro work. Use a small aperture (e.g. f/22) against a light backgound. Any dust that usually doesn’t present itself as a serious flaw on most images will reveal itself as huge boulders on the macro images if you’re trying to get max depth of field– at least they did on mine.

Incidentally, I followed the procedures in the manual for cleaning the sensor and it worked like a charm, except one stubborn ‘boulder’. Since I work about 10 minutes from the Singapore Canon Service Centre I brought it in and they had it clean as a whistle in just a couple minutes, free of charge.

Hopefully this saves somebody from experiencing the same thing I did.
Regards,
Roy
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Old Apr 10, 2003, 10:34 PM   #2
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Good advice.

I have a separate question for you. How do you like that macro lens? I'm been thinking of getting something for Macro work, but I've only just started the research.
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Old Apr 11, 2003, 12:03 PM   #3
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eric_s,
Iím relatively new to macro photography and therefore donít have much to compare the 100mm macro with - this is my first quasi-true macro lens (i.e. 1:1). That said, I do like the lens. Iíve never had so much Ďfuní with a lens before. I primarily use it outside and am still struggling to get really crisp images at small apertures usually due to subject movement. But when I get it right the images are great. I think a lens like this can really tests your skills. I try to use existing light where possible but, more than not, itís impossible with some of the skittish creatures Iím dealing with while maintaining sufficient depth of field. Also, the slightest whisper of air movement creates havoc with a large flower under this magnification Ė timing seems to be the the key; knowing when to release the shutter. I canít afford a dedicated macro flash now, so Iíve been experimenting with my Speedlite (off-camera). I find when held at a 45% angle to its usual on-camera position, and the flash face in the same plane as the front of the lens, it produces pretty good results. If anyone has other tips on using a single flash for macro work, Iíd love to hear them.

For the most part I donít find the auto-focus on the 100mm very useful for macro work. If there is slight subject movement, it usually zooms into oblivion for a few hours (or at least thatís what it seems like). It may be just me, but I get better results when I keep the focus on manual and move the camera position slightly instead, albeit sometimes difficult while in an awkward position on the tripod. Auto-focus for the non-macro shots is very quick and responsive, but not quite up to the capabilities of my 28-70mm L (which, incidentally, is the reason I canít afford the macro flash). Iím going to Thailand next week and hope to give the macro a workout there....

BTW, since getting the 28-70mm L, Iím finding it tougher and tougher to use my non-L lenses with the exception of the 100mm macro Ė both are wonderful lenses, and the wide 2.8 aperture is extremely useful in low light. I was lucky to get my shopís last 28-70mm L at a good price before they brought in the replacement 26-70. If you can find a 28-70 and can afford it, buy it. Chances are it wonít be there by the time you convince your spouse and go back. Iím now saving for the 16-35mm L. Anybody wanna buy a car...
Regards,
Roy
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Old Apr 12, 2003, 11:15 AM   #4
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Thanks for the advice. I greatly appreciate it.

I actually know a place which has the 28-70L used. Maybe I should jump on it. Humm. Part of me likes the longer range and IS of the 28-135L (?), but I saw a comparison between it and the 28-70, and the 28-135 fell down badly. It just wasn't nearly as sharp. Sigh. What's $500 more anyways? (I wish!)
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