Disassembly – 7artisans 12mm F2.8 lens

Finally I found some time to discover more details about 7artisans 12mm F2.8. I’ve been sparingly shooting with it and posted some samples from Fuji X-E2s on related Flickr public group .

I’ve recently reviewed 7artisans 12mm F2.8 on 35MMC , and during that review noticed that aperture blades are not completely opened at F2.8. Another reason for the disassembly was quite large dust particle under the rear glass in my sample.

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7artisans 12mm F2.8 lens. The custom drop of red paint just helps to read F value faster.

7artisans engineers designed this 12mm ultra-wide lens without filter thread, though I see that the metal ring with letters around front glass is sitting in thread. I was not able to easy unscrew it so skipped frontal disassembly for the next time.

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7artisans 12mm F2.8 lens – FX-Mount

My lens sample has Fuji FX-Mount secured with three Torx bolts. It’s important to remember each bolt location (you’ll see later why). So gently unscrew them and store in exact order.

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The Torx bolt closer to the mount lock hole has few thin aluminum shims. They simply serve to lift bolt head position, so camera locking pin will pass the bolt without catching its position. 7artisans engineers are using good amount of blue securing adhesive.

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Once the mount is removed you can see that aperture ring is connected to the inner aperture mechanism through the separate (lighter gray) transmission ring. Just pull the aperture ring up to remove it. The ring can be put back in reverse order so check the aperture numbers orientation during the assembly.

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You can skip unscrewing the brass pin (like it’s needed for 7artisans 35mm F1.2 disassembly), the aperture transmission ring can be easily pulled up.

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7artisans 12mm F2.8 – aperture transmission ring

The aperture transmission ring rotation is limited by the outer brass pin. However once it’s removed you can use tweezers to gently move inner brass pin that controls the aperture blades. Surprisingly it can be moved CW a little furhter!

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7artisans 12mm F2.8 – inner brass pin position at F2.8
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7artisans 12mm F2.8 – inner brass pin position rotated CW much further than F2.8.

You can see that aperture opening is now perfectly round! I’ll experiment with it in my new post to see how it affects the image. The opening area is not significantly bigger, so we can’t say it’s more than F2, so I’ll call it “F2.?” , OK? I suppose 7artisans engineers initially created the aperture module to be opened wider, but probably opening was too wide for F2.8 so the production samples are fine tuned to stop aperture opening at that point that fits F2.8.

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There is quite massive (but light) aluminum ring around the rear glass. It can be simply unscrewed CCW without any tools. But be careful! Nothing is holding the glass inside to fall out, so better keep the lens  facing front element down.

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Here’s the final stage of this particular disassembly. It unveils access to four rear glass elements of 7artisans 12mm F2.8, that can be gently pulled out, cleaned, and inserted back (which I successfully did and cleaned the dust).

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Here’s my article on 7artisans 12mm F2.8 wider aperture opening mod.

12 comments

  1. Hi Iurii

    If you haven’t guessed already, I’m nar53 over on the Fuji-X forum. So I’ve given my copy a good looking at this morning & luckily I can’t see any dust. However mine too has the not fully open aperture. Before I pull my lens apart to adjust it can you tell me if on re-assembly can you maintain the increase in aperture size?

    Cheers, Nigel

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  2. I feel you are probably the right person to ask this question:

    Do you think it is possible to change the existing bayonet mount to a Sigma SA mount? My idea is to remove the existing mount and use a M42 to SA mount adapter and drill (if needed) the 3 fixing holes into the adapter.

    Two things on my mind are:

    1.) The 44mm Sigma SA flange focal distance (Canon EF uses same)
    2.) Can the M42 adapter (inner diameter = 41mm) fit over the black inner part of the lens

    Reason is the lack of SA mount lenses, there are also very few very wide angle M42 lenses.

    Happy new year!

    Jens

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    • Hi Jens, thank you for very interesting question. I think it is possible.
      The diameter of inner focusing module rear area is about 28mm, so it will definitely fit inside M42-SigmaSA ring.
      Idea of replacing 7Artisans mount ring to M42-SigmaSA ring is very good. You just need to test if the lens can be positioned close enough to SigmaSA camera mount to fit the adapter thickness, and keep proper focusing range.
      BTW, 7Artisans 12mm should have a bit of focusing calibration range, though it’s quite limited due to very little distance is needed to focus 12mm lens.

      Liked by 1 person

      • What worries me it the flange focal distance. Do I need to match what the lens was designed for?

        Sigma SA uses 44mm, Sony E 18mm, OM 46mm, Canon also uses 44mm.

        So when the new adapter hat the same thickness as the original, in case I use Canon EF, it should be a perfect fit? Or are there any other adjustments?

        An optically better lens would be probably the Laowa 9mm (more expensive though). The 9mm is very tempting.

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        • Jens, sorry I missed the point that your camera still requires 44mm flange focal distance. Your concern is correct – it will NOT be possible to move 7Artisans 12mm lens so much closer to the sensor. Most modern mirrorless lens are designed to sit very close to the sensor to make systems more compact and because there is no need to save space for the mirrors chamber.
          What exact camera do you use?

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          • I had some hope since the 12mm also comes in a Canon EF version, but that is EF-M (for APS-C) and requires a 18mm flange focal distance. The Laowa 9mm will be most likely the same. This is probably the point where I can end my research with a ‘can’t be done’.

            I have a Sigma SD Quattro. It has “interesting” colors and is amazing in b/w (people think I shot film). Hard to find lenses with SA mount though and I miss a very wide angle lens (I use a Canon FD 17mm on my Sony a7 and like that format). I have the Sigma 17-70mm zoom, but since it’s APS-C the 35mm format is more like a 28mm lens,

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  3. Just checked more details on Sigma SD Quattro, looks like there is a filter between sensor and mount chamber that will definitely not allow to move mirrorless lens close enough even if the lens diameter is smaller than mount inner diameter, so yes it’s time to consider DSLR lens alternatives. I used to shoot with APS-C lens Tokina 11-16mm F2.8 which is 16.5-24mm in 35mm format, it’s exceptionally great lens though a bit large and lacking external control of aperture, I’d think if it’s reasonable to adapt it on Sigma. I’d also consider Samyang/Rokinon 14mm F2.8 manual focus lens.

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  4. Hello, can you tell me why by training the 3 screws of the barrel I cannot adjust the focus of infinity? Even without the screws, the lens body moves together with the ring. Thank you

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    • Sounds like in your lens sample external focus ring sits quite tight on top of internal focus ring, so even after removing 3 screws internal friction resistance keeps it on place. Please try to remove all three screws completely, then focus to middle position and try to shift focus ring up/down a little, and try to rapidly turn it left/right to about 5-10 degrees to help loosening it from internal focus ring.

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