Squiggly (dirt?) lines on MP-E 65mm lens

[traveler582]

Has anyone come upon this problem using the MP-E 65mm lens where you get these squiggly lines across the image?

I'm using a Canon 6D with the lens and also stack images for my macro work.

I've been told it's dirt and that this is common for this lens, especially if you change lenses often (which I really don't).

I've cleaned both ends of the lens yet it doesn't seem to always help.

Is this something I just have to live with? I am able to photoshop them out, but I find it annoying...

Thanks!

[RobertTheFat]

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@traveler582 wrote:

Has anyone come upon this problem using the MP-E 65mm lens where you get these squiggly lines across the image?

I'm using a Canon 6D with the lens and also stack images for my macro work.

I've been told it's dirt and that this is common for this lens, especially if you change lenses often (which I really don't).

I've cleaned both ends of the lens yet it doesn't seem to always help.

Is this something I just have to live with? I am able to photoshop them out, but I find it annoying...

Thanks!

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Lens dirt that matters is usually inside the lens; otherwise you could just dust it off (which you did). So you should probably have the lens professionally cleaned. If that doesn't cure the problem, have the camera's sensor cleaned. (Although I agree that it's probably inside the lens, since not all of the contaminants are in focus.)

Note, however, that dirt inside the lens has little or nothing to do with how often you change lenses. It has more to do with how often you use the lens, since dirt usually gets sucked in during focussing or zooming. Dirt on the sensor is what you get from changing lenses.

[traveler582]

In response to your post RTF; since I'm stacking photo's, most of my shots take about average 90 shots, on occassion 150, and a few times up to 200. That's for one insect pose. 

Hundreds and hundreds of photos with the body and lens.

[TCampbell]

There's really no focal point "inside" the lens.  If you deliberately placed dirt in the lens it would not show up in an image.  But now that you explain that this is actually a focus-stacked image, it makes more sense that dirt could appear to migrate if the camera is on a focus rail.

Have you checked to see if this is dust on the sensor?

Put any lens on the camera, use a very high f-stop (e.g. f/22... or even f/32 if the lens supports it) and then take a photo fo a plain white wall or ceiling.   Any dust on the sensor would be visible in that shot, but that means you'd need to clean the sensor.

It's not technically the sensor, but the low-pass filter in front of the sensor (this is the thing that vibrates to shake off the dust when you power the camera on or off.)  

I find that sometimes simply removing the lens, pointing the camera at the ground, and using the menu to invoke the sensor cleaning cycle may be enough to clear it.  If that doesn't work, I use a hand-squeezed blower (like a Gioto Rocket Blower) -- avoid cans of "compressed air" because they use a liquid propellant and if that can is not perfectly level it can spew propellant onto the sensor and it leaves a residue which then has to be wet-cleaned.

I also keep a pristinely clean brush (and I give it a few solid whacks with the brisles hanging off the edge of my desk just to force it to shake loose any dust that might possibly be on the brush) and gently brush the sensor if the air squeeze bulb didn't clean it.

If that isn't enough... I grab my mangifier (sensor scope) and inspect to see what's actually on it so I know what I'm dealing with... then use "Eclipse" cleaning solution (by "Photographic Solutions").  This is a solution of nearly pure methanol so it evaporates without leaving any residue.  Photographic Solutions also makes the "sensor swabs" that go with the solution.  Use once, throw away. 

[TCampbell]

I don't think that's dirt.  It looks like something was moving in your image.

There are very few points along the optical path in which something is able to come to focus.  I've taken a tiny piece of paper (a post-it note cut down to about 1/4" x 1/4" square), stuck it on a filter, and attached it to the front of the lens just to demonstrate that this will NOT show up in the image.  Dirt cannot show up in an image unless it's located at a focus point in the image path.  Typically that's at the focus distance and also at the sensor.  

Also... these squiggles look like something was moving.  Dirt is normally not going to move.  So this makes me wonder... what were the exposure settings for this shot?  What was the aperture setting and how long was the shutter open?  Also what was the camera orientation (was it below the insect and pointing upward, by chance?)  It almost makes me wonder if the camera could possibly have imaged floating bits of dust in the air... which is why I'm wondering how long the shutter was open.

[traveler582]

In response to your post TC;

My settings are shutter speed of 200, but the MT-24EX only sync's at 1/180 sec. ISO auto (comes in @ 400), f/5.6 with the mirror locked in the up position and the lens at 5X, in RAW setting.

I use the stackshot rail system and can take upwards of 200 per insect pose, but normally average 90 per pose. Hundreds of pictures over time. The SS is set at 40um, auto number of shots. 

The attached picture was cropped since the most of the squiggly lines appear in the upper right side. Some actually appear to be different colors. I try to take the straight on shots at the face, I can't angle the camera since it's fixed.

[ScottyP]

All the squiggles are aligned in a uniform pattern and are basically the same shape as the ones next to them. Tim must be right that they were points of dirt but the focus stacking is making them appear to stretch.
I assume that if you took a single shot rather than stacked shots the squiggles would just be points/specks?

[traveler582]

Very interesting about them just being specks and the focus rail is elongating them through the series of stacks!!!

Thx!

[Skirball]

Definitely a stacking error.  As you focus the lens zooms in/out slightly, so little specs such as dirt/shadows/light/etc will move location.  Probably just little imperections on the background that are showing in the sidelight.  The program tries to align based on small sections of a pattern it can match up, but it can't match up single points or specs.  So it just stacks them up as it moves to align all the photos, and you get those squiggles.

As a side note, 90 frames is a lot, and 200 is kind of insane.  If you're getting good results, by all means, knock yourself out.  But personally I found I had better results giving the computer less options to think about, and it certainly decreased compiling time.

BTW, what software are you using?

[traveler582]

My system as shown above is anchored (maybe not the best way, I know, but tied down) and I use the StackShot automated rail system for focus stacking along with Zerene Stacker software. 

I pick a start point of focus on the insect and a stop point of focus. The camera moves along the rail and takes the shots automatically. At 5x depending on the angle of the insect could determine how many stack shots, or how much you want in focus. If he is mounted sideways, probably less. Lengthwise it could be 200 stacks, if only a small portion of the head maybe 40. It all depends..

I'm a beginner, not an expert, but have taken some nice in focus shots, and semtimes using 150 stacks...