Sensor Spots and f-Stop: I just noticed while cleaning up some photos that some appeared to not have spots while others did, same lens. The difference was the f-stop. f5.6 cannot see...

malaneystuff Loc: SE Wisconsin

I just noticed while cleaning up some photos that some appeared to not have spots while others did, same lens. The difference was the f-stop. f5.6 cannot see any. f14 they begin to appear. Did some followup testing and it was consistent the higher (smaller) the f-stop the more pronounced the spots. This was the same for multiple lenses. I'm using a Nikon D7100. Its there a reasonable explanation for this?

Thanks

wdross Loc: Castle Rock, Colorado

malaneystuff wrote:

I just noticed while cleaning up some photos that some appeared to not have spots while others did, same lens. The difference was the f-stop. f5.6 cannot see any. f14 they begin to appear. Did some followup testing and it was consistent the higher (smaller) the f-stop the more pronounced the spots. This was the same for multiple lenses. I'm using a Nikon D7100. Its there a reasonable explanation for this?

Thanks

There is likely to be contamination on the front or rear lense elements. If it is not there, then it is likely inside on the front or rear element. My bet is on the rear lens element.

f8lee Loc: New Mexico

Actually, dust on the sensor can be rendered visible at smaller apertures - odds are that is what you are seeing.

Obviously you can test this by putting a different lens on the camera and shooting a few frames wide open and then stopped down (use an area of sky or light colored wall to allow for the best visibility of the spots).

oafrank Loc: Cedar City Ut and Beaver Dam AZ

Multiple lens!!!!!! Sensor dirty

MT Shooter Loc: Montana

malaneystuff wrote:

I just noticed while cleaning up some photos that some appeared to not have spots while others did, same lens. The difference was the f-stop. f5.6 cannot see any. f14 they begin to appear. Did some followup testing and it was consistent the higher (smaller) the f-stop the more pronounced the spots. This was the same for multiple lenses. I'm using a Nikon D7100. Its there a reasonable explanation for this?

Thanks

Smaller apertures yield greater depth of field causing the sensor dust spots to become more pronounced.
You will also notice many more at the top of your image than the bottom of it. That is because your image is inverted from how the sensor captures it and your cameras automatic sensor cleaning shakes the dust to the bottom of the sensor.

wdross Loc: Castle Rock, Colorado

oafrank wrote:

Multiple lens!!!!!! Sensor dirty

I am mistaken! OP DOES say multiple lenses.

juanbalv Loc: Los Angeles / Hawthorne

No the mistake is all yours. OP stated multiple lenses.

wdross wrote:

I am mistaken! OP DOES say multiple lenses.

GoofyNewfie Loc: Kansas City

MT Shooter wrote:

You will also notice many more at the top of your image than the bottom of it. That is because your image is inverted from how the sensor captures it and your cameras automatic sensor cleaning shakes the dust to the bottom of the sensor.

I never thought about the dust spots being more likely to be on the upper part of the image, lower part of the sensor.
I just thought it was because the top part is usually lighter with sky. Will have to watch for that.

MT Shooter Loc: Montana

GoofyNewfie wrote:

I never thought about the dust spots being more likely to be on the upper part of the image, lower part of the sensor.
I just thought it was because the top part is usually lighter with sky. Will have to watch for that.

I guess you learned something new today then!

LoneRangeFinder Loc: Left field

MT Shooter wrote:

Smaller apertures yield greater depth of field causing the sensor dust spots to become more pronounced.
You will also notice many more at the top of your image than the bottom of it. That is because your image is inverted from how the sensor captures it and your cameras automatic sensor cleaning shakes the dust to the bottom of the sensor.

GoofyNewfie Loc: Kansas City

MT Shooter wrote:

I guess you learned something new today then!

That’s always good!

jcboy3

MT Shooter wrote:

Smaller apertures yield greater depth of field causing the sensor dust spots to become more pronounced.
You will also notice many more at the top of your image than the bottom of it. That is because your image is inverted from how the sensor captures it and your cameras automatic sensor cleaning shakes the dust to the bottom of the sensor.

Depth of field is not the issue when dealing with sensor dust spots, and only marginally when dealing with spots on the lens. The actual mechanism is simply that the larger aperture will focus light from a wider path through the lens, and the spots are thus relatively smaller. Stop down the aperture, the light path is narrower, and the spots are proportionally larger and thus more visible in the image.

MT Shooter Loc: Montana

jcboy3 wrote:

Depth of field is not the issue when dealing with sensor dust spots, and only marginally when dealing with spots on the lens. The actual mechanism is simply that the larger aperture will focus light from a wider path through the lens, and the spots are thus relatively smaller. Stop down the aperture, the light path is narrower, and the spots are proportionally larger and thus more visible in the image.

You are welcome to believe whatever you wish.

jcboy3

MT Shooter wrote:

You are welcome to believe whatever you wish.

How very kind of you.

Joe Blow

malaneystuff wrote:

I just noticed while cleaning up some photos that some appeared to not have spots while others did, same lens. The difference was the f-stop. f5.6 cannot see any. f14 they begin to appear. Did some followup testing and it was consistent the higher (smaller) the f-stop the more pronounced the spots. This was the same for multiple lenses. I'm using a Nikon D7100. Its there a reasonable explanation for this?

Thanks

While it helps if you had posted some shots with and without, I'm going with a dirty sensor.

Remove the lens and lift the mirror. You might need to read the manual for that. With a blower, give the sensor a good blow. If your blower has a brush, gently clean the sensor.

Put the mirror down and put the lens back on. Shoot a blank wall and see if the dust is still there.

Good luck.