Canon MP-E65 - Getting weird spots in images

[ktuli]

All,

I've been seeing these spots from time to time in some of my images, and I was starting to think that I had dirt or something on my sensor. My 7D has the auto-clean cycle that runs every time the camera is turned on and off, plus I've run the manual internal sensor cleaning cycle a couple times. I was all set to either clean the sensor myself, or take it to a shop for cleaning, when I noticed the spots where not there when I used my 100mm lens the other day.

So I ran a little test... I took a photo with my 100mm macro, then with the MP-E 65mm at 1x magnification, then a couple at 5x magnification. Sure enough, the spots only show up (at least that I can tell) when I have the lens at 5x magnification. The spots are always in the exact same locations, so whatever the problem is, I don't think it is going away.

Does anyone have any ideas what these might be? I just want to have a pretty good idea of what is happening before I go about trying to get the seller or Canon to replace the lens...

I just took photos of a piece of paper real quick to illustrate this. Is there something better I should use to illustrate the problem?

100mm macro:


mp-e 65mm at 1x:


mp-e 65mm at 5x:



Any and all help is greatly appreciated!

- Bill

[William W]

Stick another lens on it (the 100 macro will do) set to ∞ focus and set Aperture to F/22 and take a shot of clear blue sky and then pixel peep – if the spots are in the same place then my bet is that they are small specs of dirt or grim on the sensor.

WW

[Steve S]

Do what william said, but pull up photoshop and fill a layer with sky blue. Turn to highest f/stop and don't worry about focus, turn it off. Hold the camera infront of the computor screen and move it in small circles untill the exposure is complete. Then upload the photo and you will see any dirt on the sensor.

The dirt that gets on the sensor , sometimes won't fall off from the auto sensor cleaning. It is more like a water spot on a glass. It has to be removed manually. It's not a big deal to clean it. If you want i'll walk you through the cleaning process. You'll have to order some supplies first though.

[Snarkbyte]

Ditto previous responders comments. Meanwhile, you might try the "Dust Delete Data" function of the 7D; see pg. 185 of the 7D User's Manual.

[William W]

. . . pull up photoshop and fill a layer with sky blue. Turn to highest f/stop and don't worry about focus, turn it off. Hold the camera infront of the computor screen and move it in small circles untill the exposure is complete. Then upload the photo and you will see any dirt on the sensor.

Love your technique!

Very suitable, it has been raining here all week!


WW

[ktuli]

The spots do not show up with another lens... heck, they don't even show up with the same lens at 1x magnification. They only appear when I put the lens at 5x magnification.

- Bill

[William W]

. . . Then logic dictates it is more likely something to do with the lens . . .
so get (borrow) another camera . . . and do the same test with that lens.

WW

[Steve S]

It really looks like dirt on the sensor to me. Did you check it like suggested? (dirt spots on a sensor will only show up when the f/stop is cranked up to 11 or better. Do a quick check of the sensor with another lens on. If it is dirt, it will show up in the same place. If not, you might have some dirt specks in the lens.

[revi]

If you judge the spots on your pictures of the paper (as shown here), then don't be misled by the paper structure. Such a structure can easily hide the spots, so you'll really have to do the tests on a homogeneous surface. That's also the reason to do the test with the subject out of focus (to smooth out any texture left in the subject).

Also, try the test with very small and very large apertures:
- dust spots on the sensor will show up at F16 and over (and might be invisible at F5.6 or lower) (dirt in the lens might show a different behaviour)
- sensor problems (dead pixels) would show up independent of F-stop.

As to why the spots would show up at the 5x magnification and not at the 1x:
at 5x you 'spread out' your texture, so the spots are easier to recognise for what they are, since they have become smaller than the paper structure (different frequencies), at 1x the spots and the paper texture have about the same 'frequency' in the texture.

[Jim B.]

From the review site "The Digital Picture".

The Canon MP-E 65mm Macro Lens also enlightens you to a whole new world of sensor dust. Make sure your sensor is spotless - or plan to spend a lot of time with Photoshop's healing brush!

[rene3580]

Hello,

I have the same problem.
This are minimini dust particles, that are still or again there after cleaning the sensor.
As far as my experience: they are always there...

Regards,

René

[William W]

I agree. . . but do use the lens on another camera, just to show that the spots are in a different place. . . and "it is someting to do with the lens."



WW

[ktuli]

Excellent point - I will put the lens on my Rebel XT tonight. If it is sensor dirt, then I'd expect spots, but in different places (that camera is old enough that I can almost guarantee it has sensor dirt). If it is lens based, then the spots will be in the same places that they appear on the 7D.

I'll be trying the other tests as well for sure, but this one will definitely say whether the problem is lens based or not.

- Bill

[ktuli]

Sure enough, the additional techniques provided helped to draw this out... it is definitely dirt on the sensor. Looks like it is time to do some more thorough sensor cleaning.

Thanks for all the help everyone! Greatly appreciated!

- Bill

[William W]

Sure enough, the additional techniques provided helped to draw this out... it is definitely dirt on the sensor. Looks like it is time to do some more thorough sensor cleaning.

Or never use that lens at 5:1 macro. . .

[DanK]

the greater the magnification, the smaller the dust spots that will show up.

I agree that you should not test this with paper, particularly with a high level of magnification. I use this instead of sky:
http://www.pbase.com/copperhill/image/95174363/original


If you have not cleaned a sensor before, you can find lots of advice, but here is my drill, for what it is worth:
1. Use a big rocket blower, with the camera positioned with the sensor at the top. do NOT use canned air.
2. If that does not work, I use a static brush, again in the same position.
3. If that also does not work, I give in and do a wet cleaning. I have only had to do two or three--the first two steps usually suffice.

I use Copper Hill's materials--not too expensive, and they have very good tutorials.

[Glenn NK]

To check for dust spots on a sensor, it is not necessary to shoot any particular sky; a cloudy sky will do. You can also shoot a light coloured ceiling - just make sure it's well out of focus.

Set the lens to minimum focus distance and a small aperture - f/16 or smaller. The point is to not have anything in focus that could project onto the sensor - leaving only spots on the sensor itself that will show up in the image.

The nice thing about shooting the sky or a ceiling is that most of us have access to the sky during the daytime, and many also have a ceiling to use in the night time.

Glenn

[ktuli]

Or never use that lens at 5:1 macro. . .

Kind of defeats the purpose of spending the money on the only lens on the market today that does 5:1 macro if I never use it at 5:1 macro.... That is the whole reason I bought this lens.

[revi]

the greater the magnification, the smaller the dust spots that will show up.
...

That depends on what magnification you talk about... If it's the magnification of the image on screen, then yes, until you see individual pixels.
If you mean the magnification wrt the subject (as in macro photography), then no, magnification won't play a role, as the spots are formed on the sensor, independent of the subject. All that can happen is that tonal changes in the projected image can hide the dust spots, but they'll still be there.

[ktuli]

Glenn and Dan,

Thank you for the additional comments. Yes - I did end up using a wall to shoot my tests. I used the combination of defocusing the lens as well as moving the camera during exposure - that certainly made the sensor dirt spots stand out.

Additionally, it made it *very* apparent that I also need to clean my XT's sensor as the dirt spots found there were much larger.

Luckily, having the XT also means I have a practice camera to work on before working on my main camera - the 7D. I have tried the rocket blower already, and that didn't even budge the spots. Additionally, the internal sensor cleaning cycle did nothing to them either... so I'm betting this'll end up being what Steve first mentioned, which likely means a wet cleaning.

- Bill