This 250mm f/4.9 lens is the “world’s sharpest” and has interchangeable camera mounts

Feb 21, 2019

John Aldred

John Aldred is a photographer with over 20 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.

This 250mm f/4.9 lens is the “world’s sharpest” and has interchangeable camera mounts

Feb 21, 2019

John Aldred

John Aldred is a photographer with over 20 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.

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It’s a pretty bold claim to say you’re the world’s something-est anything. But that’s what William Optics are doing with their new Redcat 250mm f/4.9 lens, hailing it as the “World’s Sharpest” 250mm lens ever made for full frame cameras. Which, to be fair, is possibly true, as very few 250mm lenses have ever been made for full frame cameras.

Interestingly, though, it’s based on a Petzval design, which is typically more associated with “swirly bokeh” than sharpness. But this lens uses a pair of synthetic fluorite elements to correct those issues in an attempt to produce sharpness across the entire frame. At least, that’s what their Kickstarter campaign says.

YouTube video

Designed primarily for astrophotography, Taiwan based William Optics is no stranger to such application. Their About section says that they’re “one of the world leaders in short-tube, highly-portable refractors”, producing equipment at both entry-level and high ends of the user spectrum.

The new lens, known as the RedCat 51 APO 250mm f/4.9 is a fast Apochromatic refractor that’s both small and lightweight with a full frame 35mm field of view. As mentioned, it uses a Petzval design with synthetic fluorite elements to produce a flat field image and overcome the issues inherent with the Petzval design.

Looking at the sample photos on the campaign, as well as this footage shot on the Panasonic GH5, it certainly does seem to live up to its sharp claim. Whether it’s the sharpest or not will have to wait until we can see some real side-by-sides, but for now, I think it’s definitely sharp enough.

YouTube video

Of course, the Panasonic GH5 is a 2x crop body, not full frame. So, again, we’ll have to see how well it performs on full frame once the lens ships and is out there in the world for people to play with.

One of the interesting things about it, is that it comes with an interchangeable lens mount. Essentially, it’s an M48 thread, and adapters will be available for Nikon F, Canon EF, Pentax K, Sony E and Micro Four Thirds. But the design offers future-proofing for other cameras, like the Nikon Z mount, Canon RF, and Leica L. All it needs is a new adapter.

  • Focal length: 250mm
  • Diameter: 51mm
  • Aperture: f/4.9
  • Format: Full Frame, APS-C & Micro Four Thirds
  • Image Circle: 44mm
  • Mount: Nikon F, Canon EF, Pentax K, Sony E & Micro Four Thirds (interchangeable)
  • Optics: 4 elements in 3 groups (Petzvcal)
  • Dimensions: 225 x 80mm
  • Weight: 1.47kg

It’s an interesting lens, that looks rather good for wildlife as well as astro, given the footage above and the sample photos on the campaign page. I’m curious how well it would work for portraits, although being a manual focus lens, I’m not curious enough to back the project myself.

If you want to, though, you’ll want to hurry. It’s already doubled its funding goal, and only has three days left to go. You can pledge through Kickstarter now for $649 (93% of the final retail cost once the campaign’s over), which includes the lens, Nikon Canon or Sony mount adapter, a soft carry case and their patented Bahtinov Mask. Lenses are expected to start shipping at some point in March.

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John Aldred

John Aldred

John Aldred is a photographer with over 20 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.

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20 responses to “This 250mm f/4.9 lens is the “world’s sharpest” and has interchangeable camera mounts”

  1. Tj Ó Seamállaigh Avatar
    Tj Ó Seamállaigh

    Check Astrobackyard on youtube. His last 2 videos (or maybe 3 can’t remember) goes through this lens and its specs. He uses it as a telescope on its own.

  2. Stewart Norton Avatar
    Stewart Norton

    World’s sharpest 250mm f4.9 lens…how many others are there…none, so claims are sort of true ?

    1. just me Avatar
      just me

      That’s what I thought. I can’t think of any other 250mm lens and I am 67. Can anyone help out here? Making a claim that It’s the sharpest 250mm out there where are no others is….by definition…a true statement, but…..

    2. CrashingOut Avatar
      CrashingOut

      It’s in a class of it’s own truly, as it’s designed for astrophotos the optical standards it has to deal with are already extreme. Using anything but the finest DSLR lenses for astrophotos is comical folly – this Petzval lens design should equal or outperform even exotic high speed flagship glass from any camera maker.
      I really effing want one ha.

  3. Duncan Knifton Avatar
    Duncan Knifton

    beats the white Canon lenses ;)

  4. Jia Chen Lu Avatar
    Jia Chen Lu

    Autofocus?

    1. Duncan Knifton Avatar
      Duncan Knifton

      Looks manual focus to me.

    2. Blane J. Nasveschuk Avatar
      Blane J. Nasveschuk

      Take a look at Deep Sky Dad’s AF3 with RedCat 51 f4.9. There are some setup options to consider, as usual. AF3 ASCOM compatible.

  5. Alexander L. Harris Avatar
    Alexander L. Harris

    Well it’s definitely not subtle.

  6. Milky Avatar
    Milky

    Trevor from astrobackyard does a fine unboxing and review.

    This is great because it doesn’t need a flattener. But at 250mm and this price, I’d go for the z61 or a 72mm Apo. If you like refractors that is.

  7. Kryn Sporry Avatar
    Kryn Sporry

    Who cares how the lens looks? And how to judge its results on a phone…?

  8. billss Avatar
    billss

    Interchangeable mounts. I wondered when someone was going to finally do that.

    1. Paul Kent Avatar
      Paul Kent

      Someone like Tamron in the 70’s?

      1. billss Avatar
        billss

        Good one Paul…didn’t know that…I was in high school in the 70’s…no money for camera gear! :)

        1. Paul Kent Avatar
          Paul Kent

          Hopefully the were be more interchangeable mounts and at a time when we have more money.

          I may buy a few Sigma lenses because they can at least be sent in for conversion.

  9. Alexandru Busuioceanu Avatar
    Alexandru Busuioceanu

    interchangeable lens mounts, nothing could go wrong there

  10. David Art Avatar
    David Art

    Good decision not to make a Fuji mount, I will stick with Fujinon

  11. Jarno Kylmänen Avatar
    Jarno Kylmänen

    …when the red stripe on your lens isn’t enough ?

  12. Floh Poschenrieder Avatar
    Floh Poschenrieder

    Kai Rademacher evtl was für dich

  13. just me Avatar
    just me

    I just replied to Stewert Norton…..can anyone think of another 250mm lens? I’m struggling with this .To make this claim is…by definition…true if there are no other 250mm lenses out there, but……