Thickness of Aluminum Foil

Started Aug 25, 2017 | Discussions
Marianne Oelund Veteran Member • Posts: 7,788
Thickness of Aluminum Foil
19

A web source says it's about 0.016mm for typical kitchen grade, and 0.024mm for heavy-duty grade.  I found out that's about right.

Why do I care?

A number of about that magnitude popped out of my calculation, when I went to figure out how much image tilt there is at the sensor, with my 105/1.4E.  When I was running field-curvature checks a few months ago, I found that a number of my lenses have various degrees of field tilt (focusing slightly closer on one side, than the other).  The 105 had a moderate amount, but it was enough to show up in astrophotography, even when stopped down to f/2.8.

Being adventurous, and not wanting the performance of an otherwise very fine optic to be compromised, I started experimenting by inserting various shims, made of - you guessed it - aluminum foil.

I wasn't too excited about the prospect of removing the lens mount ring multiple times to fiddle with the shims until I had a good solution (too many tiny screws involved), so I decided to start with my D800E's mount ring, which only has 5 of the larger screws to remove and replace.

It only took a few tries to find a shim arrangement that worked well, then I transferred it to the lens and gave it a final test.  I'm very pleased with the outcome, especially after taking some astrophotos with it, and ending up with equally-focused corners.  A very satisfying result, and I'm especially pleased that the lens won't be needing the multiple trips to Nikon service that probably would have been required.

Focusing for Astro

Astrophotos are basically large sets of lens point-spread functions, which make every aberration painfully obvious.  Getting focus optimized - and getting it even across the frame - takes some practice and technique.

One of those techniques requires being aware of how gravity works with, or against, your focusing mechanism.  You always want to move the focus group in the direction that goes against gravity, so the focus group will be resting against the helicoid and any backlash in the cams/followers is taken up.

Usually this means starting with focus a little past infinity, then carefully moving it closer until you have best image across the frame.  With that setting method, you can then point the lens higher and lower in the sky and expect that focus will remain where you set it, since gravity will help to hold it there.

However, on my first night out with the 105/1.4E, I got a nasty surprise when I tilted the camera vertically upwards to photograph Lyra and Cygnus which were near the zenith.  Focus went seriously tilted.  At the time I didn't understand why, but when I was working with the lens to add the mount shims, I made a point of examining how the focus group moves.  Surprise - it moves forward as you focus towards infinity, which is exactly the opposite of most lenses.

Armed with the mount shims and new knowledge of the focus group movement, I was able to obtain a very nice set of astro photos the other evening, using the 105E.

Now I just need to get busy and shim a few other lenses, some of which will require material much thicker than single-layer aluminum foil.

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Source credit: Prov 2:6
- Marianne

fishy wishy
fishy wishy Veteran Member • Posts: 9,358
Re: Thickness of Aluminum Foil

Hmm, I have a zoom that is seriously decentered at the long end and a mount screw periodically needs tightening. Since I have to take the mount off to see what I can do I might as well experiment with it.

Eric Calabros
Eric Calabros Regular Member • Posts: 203
Re: Thickness of Aluminum Foil
1

I wonder how fly-by-wire mechanism will change things in this regard

ormdig
ormdig Senior Member • Posts: 2,562
Re: Thickness of Aluminum Foil

Excellent Marianne! Your advice: "One of those techniques requires being aware of how gravity works with, or against, your focusing mechanism. You always want to move the focus group in the direction that goes against gravity, so the focus group will be resting against the helicoid and any backlash in the cams/followers is taken up." is very pertinent to any vertical fine focusing.

So....where are the images? Cygnus to Hercules is one of my favorite sections of the sky,

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Pete

 ormdig's gear list:ormdig's gear list
Nikon D7000 Nikon D800 Nikon AF-S Nikkor 24-70mm f/2.8G ED Nikon AF-S Nikkor 70-200mm f/2.8G ED VR II Nikon AF-S 105mm F1.4E ED +7 more
OP Marianne Oelund Veteran Member • Posts: 7,788
Flight Controls?

Eric Calabros wrote:

I wonder how fly-by-wire mechanism will change things in this regard

Fly-by-wire is rather important to me:  It's where I earn a living (my company makes primary and secondary flight control electronics for a number of airframe manufacturers, including Boeing and Airbus).

Other than that, I'm not sure how you are making the connection with lens-tilt correction.

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Source credit: Prov 2:6
- Marianne

maljo@inreach.com Veteran Member • Posts: 8,085
No longer ILC?

You have a body dedicated to one lens.

What if you want to use that lens on others bodies?

maljo

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Olympus E-M1 Nikon D500 Nikon D850 Olympus M.Zuiko Digital ED 40-150mm F4-5.6 R
OP Marianne Oelund Veteran Member • Posts: 7,788
Re: No longer ILC?
3

maljo@inreach.com wrote:

You have a body dedicated to one lens.

What if you want to use that lens on others bodies?

If you're referring to my opening post, then no, I was correcting a lens issue which applies to its use on all bodies, so the final shim placement was under the mount ring on the lens, not in the camera.

With over 50 different lenses on hand, and a half dozen camera bodies, it's not difficult to determine whether an issue is in the lens, or in the camera body.

Also, I didn't mention it earlier, but my D800E has a slight back-focus issue in the lower left across a large number of lenses, so I'm keeping one thin shim under its mount.

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Source credit: Prov 2:6
- Marianne

incoherent1 Contributing Member • Posts: 632
Re: Thickness of Aluminum Foil
2

Now I just need to get busy and shim a few other lenses, some of which will require material much thicker than single-layer aluminum foil.

You are aware, I assume, that shim stock is available in various thicknesses and (I think) materials. Check with a local machine shop or automotive/industrial supply store. No need to make do with 'found' materials.

 incoherent1's gear list:incoherent1's gear list
Nikon D810 Nikon AF-S Micro-Nikkor 105mm F2.8G IF-ED VR Nikon AF-S Nikkor 24-120mm F4G ED VR Sigma 50mm F1.4 DG HSM | A Nikon 200-500mm F5.6E ED VR +1 more
OP Marianne Oelund Veteran Member • Posts: 7,788
Source Reference
3

incoherent1 wrote:

Now I just need to get busy and shim a few other lenses, some of which will require material much thicker than single-layer aluminum foil.

You are aware, I assume, that shim stock is available in various thicknesses and (I think) materials. Check with a local machine shop or automotive/industrial supply store. No need to make do with 'found' materials.

Here's one source I found.  Stainless steel 301 can be obtained in thicknesses down to 0.5 mil (0.0127mm), and then in 0.5 mil increments up to 2 mil, then 1 mil increments up to 10 mil:

http://products.trinitybrand.com/viewitems/stainless-steel-shim/stainless-steel-shim-flat-sheets?

Trinity has a $30 minimum order, but a small sheet of each thickness from 0.5 mil to 2 mil will meet that.

By comparison, ordinary aluminum foil is about 0.6 mil and heavy-duty is about 0.9 mil.  Nothing wrong with using those when they are appropriate.

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Source credit: Prov 2:6
- Marianne

Leonard Migliore
Leonard Migliore Forum Pro • Posts: 18,660
Reread the original post

maljo@inreach.com wrote:

You have a body dedicated to one lens.

What if you want to use that lens on others bodies?

maljo

Marianne was just testing out the shim thickness on the camera body because it was quicker to remove the camera's lens mount than to work on the lens itself; once she found the correct shim thickness, she applied it to the lens.

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Leonard Migliore

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Canon PowerShot G12 Nikon D300 Nikon D750 Nikon AF-S DX Nikkor 16-85mm f/3.5-5.6G ED VR Nikon AF-S DX Nikkor 35mm F1.8G +11 more
lickity split
lickity split Veteran Member • Posts: 6,170
Re: Thickness of Aluminum Foil

Marianne Oelund wrote:

A web source says it's about 0.016mm for typical kitchen grade, and 0.024mm for heavy-duty grade. I found out that's about right.

Why do I care?

A number of about that magnitude popped out of my calculation, when I went to figure out how much image tilt there is at the sensor, with my 105/1.4E. When I was running field-curvature checks a few months ago, I found that a number of my lenses have various degrees of field tilt (focusing slightly closer on one side, than the other). The 105 had a moderate amount, but it was enough to show up in astrophotography, even when stopped down to f/2.8.

Being adventurous, and not wanting the performance of an otherwise very fine optic to be compromised, I started experimenting by inserting various shims, made of - you guessed it - aluminum foil.

I wasn't too excited about the prospect of removing the lens mount ring multiple times to fiddle with the shims until I had a good solution (too many tiny screws involved), so I decided to start with my D800E's mount ring, which only has 5 of the larger screws to remove and replace.

It only took a few tries to find a shim arrangement that worked well, then I transferred it to the lens and gave it a final test. I'm very pleased with the outcome, especially after taking some astrophotos with it, and ending up with equally-focused corners. A very satisfying result, and I'm especially pleased that the lens won't be needing the multiple trips to Nikon service that probably would have been required.

Focusing for Astro

Astrophotos are basically large sets of lens point-spread functions, which make every aberration painfully obvious. Getting focus optimized - and getting it even across the frame - takes some practice and technique.

One of those techniques requires being aware of how gravity works with, or against, your focusing mechanism. You always want to move the focus group in the direction that goes against gravity, so the focus group will be resting against the helicoid and any backlash in the cams/followers is taken up.

Usually this means starting with focus a little past infinity, then carefully moving it closer until you have best image across the frame. With that setting method, you can then point the lens higher and lower in the sky and expect that focus will remain where you set it, since gravity will help to hold it there.

However, on my first night out with the 105/1.4E, I got a nasty surprise when I tilted the camera vertically upwards to photograph Lyra and Cygnus which were near the zenith. Focus went seriously tilted. At the time I didn't understand why, but when I was working with the lens to add the mount shims, I made a point of examining how the focus group moves. Surprise - it moves forward as you focus towards infinity, which is exactly the opposite of most lenses.

Armed with the mount shims and new knowledge of the focus group movement, I was able to obtain a very nice set of astro photos the other evening, using the 105E.

Now I just need to get busy and shim a few other lenses, some of which will require material much thicker than single-layer aluminum foil.

Where's the pics , of the astro not the shims ?  

 lickity split's gear list:lickity split's gear list
Nikon D850 Nikon AF-S Nikkor 24-70mm f/2.8G ED Nikon AF-S Nikkor 300mm f/2.8G ED VR II Nikon AF Micro-Nikkor 200mm f/4D ED-IF Sigma 15mm F2.8 EX DG Diagonal Fisheye +11 more
photoreddi Veteran Member • Posts: 7,973
Re: Thickness of Aluminum Foil

Marianne Oelund wrote:

A web source says it's about 0.016mm for typical kitchen grade, and 0.024mm for heavy-duty grade. I found out that's about right.

...

Now I just need to get busy and shim a few other lenses, some of which will require material much thicker than single-layer aluminum foil.

There are many sources for metal foils (aluminum, copper, brass, etc.) but they tend to be quite thick. Here's one company that sells aluminum sheet foils that are quite inexpensive but at 36 guage would it be too thick?

HEAVY ALUMINUM SHEET FOIL - For embossing, Tooling & Fine Craft

http://www.whimsie.com/aluminumsheetmetal.html

.

A screen cap. of their web page is more informative than my description would have been :

.

Edit:

Here's one source I found. Stainless steel 301 can be obtained in thicknesses down to 0.5 mil (0.0127mm), and then in 0.5 mil increments up to 2 mil, then 1 mil increments up to 10 mil:

http://products.trinitybrand.com/viewitems/stainless-steel-shim/stainless-steel-shim-flat-sheets?

I should have known that your sheet metal sources would be legion.

OP Marianne Oelund Veteran Member • Posts: 7,788
Zeiss Milvus 35/1.4
6

Last winter, I set out to test a few 35mm-class lenses for astrophotography, including the new Sigma 40 Art and Nikon Z 35/1.8 S, to see how they performed compared to my other 35's.

Normally I use a rather meticulous approach to setting focus for astro, checking both center and corner for optimum focus.  In this case, I was in a bit of a hurry (it was winter), so I only optimized focus at the upper left corner.  That worked well for most of the lenses, but when I checked the images from the Milvus 35, I discovered that approach didn't work very well.  Focus gradually goes out from left to right, and not even the center is in focus:

Out-of-focus Orion.  Actual aperture f/2.2

That's a large discrepancy.  Translated to terrestrial scenes, it means that the left side of the image is focused at infinity, while the right side is focused at about 35' (11m).  That could be useful in a few special cases, but generally, it's unacceptable.

We could speculate at length, about Zeiss (Cosina) QC and how a $2000 lens ended up in such a poor state, but I prefer to skip ahead to the solution.

If you've read the opening of this thread, you already know what the solution entails:  Placement of thin shims under the lens mount ring to correct the waywardness.  My initial estimate suggested at least 0.1mm thickness, but that struck me as a large number, so being the cautious type, I started with 0.05mm.

Turns out I was being far too cautious, and 0.05mm hardly helped the problem.  So I went up to 0.1mm - but that also turned out to be insufficient.  Feeling a little exasperated, I put in some 0.2mm material, and finally, the problem was corrected, but slightly overcompensated.  Dropping back to 0.17mm, it looked virtually perfect for the distant landscape setting I was using for the test.

The next opportunity for an astro check was on a night of the full moon, so I waited until pre-dawn for it to settle lower in the sky and reduce the sky glow.  Because there was still scattered moonlight, I had to use a lower exposure.  The star images are not as bright (also because it's a less interesting area of the sky), but it's obvious that not only has focus improved, but edge aberrations are also better controlled.  There is just a mild amount of bat wing coma at the far right in this image at f/2:

It might be possible to improve the coma at the right side by dropping the shim thickness down a little more, perhaps to 0.15mm, but for now I'll leave it where it is until I have more experience using the lens in various settings.

Another calibration issue with this lens, concerns the aperture-control gearing, at least when used on the Z7.  I need to use settings about 2/3 stop narrower in order to achieve the desired true aperture.  I made some measurements to characterize the offset more accurately:

Setting - True aperture

f/1.6 - f/1.4
f/1.8 - f/1.5
f/2 - f/1.7
f/2.2 - f/1.85
f/2.5 - f/2
f/2.8 - f/2.3
f/3.2 - f/2.45
f/3.5 - f/2.85
f/4 - f/3.2
f/4.5 - f/3.5
f/5 - f/4
f/5.6 - f/4.5
f/6.3 - f/4.9
f/7.1 - f/5.6
f/8 - f/6.2

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- Marianne

SteveCooper
SteveCooper Senior Member • Posts: 1,555
Re: Zeiss Milvus 35/1.4

Hi Marianne,

You are so smart! Most of your discussion goes over my head, BUT I did find it interesting and I hope to experiment with astro-photography using a new Sigma 14-24mm f/2.8 Art lens on my Z7 when it gets a little warmer.

Do you have any pointers for a newbie?

I know I'll need to use a tripod and and remote shutter release would be preferable. Beyond that, I'm clueless.

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(that "thing" I'm playing is called an EVI, short for Electronic Valve Instrument

 SteveCooper's gear list:SteveCooper's gear list
Sony Cyber-shot DSC-F828 Nikon D500 Nikon Z7 Nikon Z6 Nikon AF-S DX Nikkor 18-105mm F3.5-5.6G ED VR +16 more
OP Marianne Oelund Veteran Member • Posts: 7,788
Re: Zeiss Milvus 35/1.4
3

SteveCooper wrote:

I hope to experiment with astro-photography using a new Sigma 14-24mm f/2.8 Art lens on my Z7 when it gets a little warmer.

Do you have any pointers for a newbie?

I know I'll need to use a tripod and and remote shutter release would be preferable. Beyond that, I'm clueless.

This is a huge topic, but it helps to know you intend to do wide-angle astro.

If you're interested in photos that include some landscape, then you just need the tripod, as you can't do very long exposures.  For this kind of astro photo, you will likely shoot wide open and at fairly high ISO to keep exposure time down.

With a Z7 at 24mm, you can go up to at least 3 sec exposure before incurring noticeable motion blur (star trailing).  At 14mm that goes up to 5 sec.  At those exposure times, shutter shock isn't really a problem; I just use exposure delay to prevent the shutter-press from disturbing the camera.

If you want to do longer exposure times (excluding landscape) then there are a number of handy devices that you can mount your camera on, which will allow it to track the moving stars.  Examples are the Vixen Polarie and Astrotrac as described at geartacular and there are many others.

The brightness of the sky may be the limiting factor to how high you can set the camera sensitivity (ISO) or exposure.  To find a good location with dark skies, there are dark-sky websites such as darksitefinder.com.

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Source credit: Prov 2:6
- Marianne

breivogel Senior Member • Posts: 2,403
Re: Zeiss Milvus 35/1.4
1

Marianne Oelund wrote:

SteveCooper wrote:

I hope to experiment with astro-photography using a new Sigma 14-24mm f/2.8 Art lens on my Z7 when it gets a little warmer.

Do you have any pointers for a newbie?

I know I'll need to use a tripod and and remote shutter release would be preferable. Beyond that, I'm clueless.

This is a huge topic, but it helps to know you intend to do wide-angle astro.

If you're interested in photos that include some landscape, then you just need the tripod, as you can't do very long exposures. For this kind of astro photo, you will likely shoot wide open and at fairly high ISO to keep exposure time down.

With a Z7 at 24mm, you can go up to at least 3 sec exposure before incurring noticeable motion blur (star trailing). At 14mm that goes up to 5 sec. At those exposure times, shutter shock isn't really a problem; I just use exposure delay to prevent the shutter-press from disturbing the camera.

If you want to do longer exposure times (excluding landscape) then there are a number of handy devices that you can mount your camera on, which will allow it to track the moving stars. Examples are the Vixen Polarie and Astrotrac as described at geartacular and there are many others.

The brightness of the sky may be the limiting factor to how high you can set the camera sensitivity (ISO) or exposure. To find a good location with dark skies, there are dark-sky websites such as darksitefinder.com.

The exposure time depends on how much blur you find unacceptable and how far you are away from the  pole.  I get acceptable milky way shots at 30 sec with 15mm lens.

 breivogel's gear list:breivogel's gear list
Panasonic Lumix DMC-LX7 Sony Cyber-shot DSC-RX10 Sony RX100 III Sony RX100 IV Olympus TG-5 +19 more
just Tony
just Tony Veteran Member • Posts: 3,676
Re: Thickness of Aluminum Foil

Marianne Oelund wrote:

One of those techniques requires being aware of how gravity works with, or against, your focusing mechanism. You always want to move the focus group in the direction that goes against gravity, so the focus group will be resting against the helicoid and any backlash in the cams/followers is taken up.

Usually this means starting with focus a little past infinity, then carefully moving it closer until you have best image across the frame. With that setting method, you can then point the lens higher and lower in the sky and expect that focus will remain where you set it, since gravity will help to hold it there.

However, on my first night out with the 105/1.4E, I got a nasty surprise when I tilted the camera vertically upwards to photograph Lyra and Cygnus which were near the zenith. Focus went seriously tilted. At the time I didn't understand why, but when I was working with the lens to add the mount shims, I made a point of examining how the focus group moves. Surprise - it moves forward as you focus towards infinity, which is exactly the opposite of most lenses.

Armed with the mount shims and new knowledge of the focus group movement, I was able to obtain a very nice set of astro photos the other evening, using the 105E.

Now I just need to get busy and shim a few other lenses, some of which will require material much thicker than single-layer aluminum foil.

Good catch on the motion direction. I could imagine wasting a night while discovering that.

Interesting read. It reminded me of the days I was doing astrophotography on a German equatorial mount, where I always made the East side slightly heavy in the balancing.

You might already know about McMaster-Carr as another good mechanical parts source with overnight shipping on, well, everything we've bought from them over the years. I've even purchased fiber optic coupling lenses from them. But that's not what they happen to be called in the catalog.

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Render unto Digital, that which is Digital's,
and unto Analog, that which is Analog's

OP Marianne Oelund Veteran Member • Posts: 7,788
Re: Zeiss Milvus 35/1.4
5

breivogel wrote:

The exposure time depends on how much blur you find unacceptable and how far you are away from the pole. I get acceptable milky way shots at 30 sec with 15mm lens.

That's image movement up to 33 microns, or nearly 8 times the sensor pitch of the Z7.

We all have different standards of acceptability, but that one falls into my category of "star trails."

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Source credit: Prov 2:6
- Marianne

just Tony
just Tony Veteran Member • Posts: 3,676
The factor of presentation size

Marianne Oelund wrote:

breivogel wrote:

The exposure time depends on how much blur you find unacceptable and how far you are away from the pole. I get acceptable milky way shots at 30 sec with 15mm lens.

That's image movement up to 33 microns, or nearly 8 times the sensor pitch of the Z7.

We all have different standards of acceptability, but that one falls into my category of "star trails."

Those may look acceptable to just about anyone if displayed not larger than about 10" on the long side. On typical LCD monitors those trails will be shoehorned into 1 output pixel. That same downsampling also helps tremendously with the noise.

Glossy prints at that size might not hold up to super close inspection.

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Render unto Digital, that which is Digital's,
and unto Analog, that which is Analog's

OP Marianne Oelund Veteran Member • Posts: 7,788
Decision aid
1

just Tony wrote:

Marianne Oelund wrote:

breivogel wrote:

The exposure time depends on how much blur you find unacceptable and how far you are away from the pole. I get acceptable milky way shots at 30 sec with 15mm lens.

That's image movement up to 33 microns, or nearly 8 times the sensor pitch of the Z7.

We all have different standards of acceptability, but that one falls into my category of "star trails."

Those may look acceptable to just about anyone if displayed not larger than about 10" on the long side. On typical LCD monitors those trails will be shoehorned into 1 output pixel.

More like two.

That same downsampling also helps tremendously with the noise.

Glossy prints at that size might not hold up to super close inspection.

A 30 sec exposure time at 15mm is equivalent to 13 sec at 35mm.  Here's an example of the latter that can be used to judge acceptability:

Z7 short star trails

Here's how I look at it:  If the appearance on a typical monitor is to be the criterion, why aren't we all still using 2-6Mpix cameras?

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Source credit: Prov 2:6
- Marianne

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