50mm f1.8 photos at f11 or higher show spot

Laryl · May 31, 2005

After viewing an aircraft shot I took this afternoon I realized how dirty my ccd is, so I cleaned it. went outside with the 50mm and shot the blue sky to check my cleaning job and noted a "fingerprint sized" spot just to the right barely of dead center of the frame. This spot is brighter than the surrounding area, bleached out looking. The edges of it are soft but it is fairly well rounded.

Trying to determine what was causing it, I took a series and found the spot shows up at F11 barely but is obvious at anything higher.. from F1.8 up to F10 I really can't see it. This lens is fairly new.. haven't really used it much other than some test shots, but those weren't something I'd catch this lighter dot on, so here I sit wondering what the heck...

Have any of you ever noted this? Is it a lens defect? ..just the way it is? .. I took shots with my zoom at 50mm and it doesn't do it, so it's definately the lens. I took shots of the sky, the garage door across the street and the clouds in a different direction over the course of about an hour... the dot remains exactly in the same spot, even after cleaning and since it seems related to the aperature.... well that's all I know.

Will really appreciate hearing from anyone with info..
Laryl

Removed User 2 · May 31, 2005

Yes, it's normal.

The 50 1.8 and the 85 1.8 show this at smaller apertures. Something to do with light reflecting on the sensor, hitting the lens and then going back onto the sensor. I'm not the expert but it's normal with that lens.

Just keep the lens at f8 and below and enjoy the crisp images it give you

Laryl · May 31, 2005

wow.. learning everyday. thanks much!

sarhento · May 31, 2005

Hi Laryl,

What do you use to clean your CCD? A major cleaning of my D1x is long overdue. I have just been using a wimpy blower and it does not do a good job.

Sarhento

Laryl · May 31, 2005

I use the eclipse/pecpads/swipe Sensor Care Kit that I picked up from Nicholas R site.. he has great instructions that come with it.

http://www.pbase.com/copperhill/ccd_cleaning

Living in the dusty desert I have to clean mine every few months.. those specks just won't go away by blowing them where I come from

nfoto · May 31, 2005

Hot-spots are caused by stray light bouncing inside the mirror box, between the shiny mirror-like surface of the imager, and the rear surfaces of the llens. The spot is perfectly circular with diffuse edges, because it really represents a Gaussian distribution of the stray light. You do see a lot more of this when you shoot in infrared, because the lens coating is much less efficient in IR.

Although the new "made in China" 50/1.8 tends to show this issue, it is by no means typical for all 50/1.8 lenses. My manual 50/1.8 doesn't have this at all, and I see more hot-spots on D70 than my D2H or D2X. This mean the camera body has an influence, too.

Other lenses I've seen with hot-spots (in IR) are 12-24 DX (on Fuji S2), 28/2 (on D70), 35/1.4 (on D70 and D2H), 105/2.8 MF Micro-Nikkor (on D70 and D2H). So this is a fairly common issue.

Removed User 2 · May 31, 2005

I was actually waiting for you to come in and explain this well...

Laryl · May 31, 2005

I'm not happy with the spot but happy to understand what causes it exactly.. bummer tho to buy a nikon lens able to shoot up to f22 and be told to be careful over F10.. sigh.

Laryl

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50mm f1.8 photos at f11 or higher show spot

Laryl

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Laryl