6 responses

  1. Greg Randall
    November 25, 2010

    Re:
    “FX lenses cannot be used on DX cameras because the final image output would only be a cropped version …”
    My old AIs (FX format) lenses work perfectly on my D200 (DX) camera. Some Nikon DX cameras will not work with these lenses but most off thr higher range will.

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  2. Mark Carroll
    March 13, 2011

    The crop factor is from the ratio for the focal length, 1.5x on most cameras that use the smaller APS-C sized sensors. This means my old 50mm lens will operate on my 35mm like a 50mm, and on my digital like a 75mm. But it is the same great lens. My zoom 300mm is a 450mm. I don’t notice any loss in my composition. BTW a DX lens gets the same CROP… read more here
    http://en.wikipedia.org/wiki/Crop_factor

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  3. Peter
    February 17, 2014

    “FX lenses cannot be used on DX cameras because the final image output would only be a cropped version of the image you wish to capture.

    In short, if you have a DX camera, don’t buy FX lenses. And if you have an FX camera, you should probably stay away from DX lenses. But if you already have a DX lens, you can use it on your FX camera.”

    ===> You really got this wrong and should correct it or drop the article. FX full frame lenses work fine on DX cameras – just multiple the focal length by 1.5. My vintage 50mm/f1.4 from my Nikon F works fine on my DX – its a fast 75mm equiv portrait lens. You cannot go easily from DX lens to full frame.

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  4. Joseph
    January 20, 2016

    It is extremely hard not to be negative about this article. The author is clearly not in-depth knowledge of photography concepts, especially sensors and lenses.

    If you are beginning with a starter DX camera, when it comes time for you to purchase your first quality lens, if you can afford the better FX lens, purchase the FX lens!!! Period!!!

    First, as the author initially pointed out but then later failed to comprehend, a DX lens will never be able to cover the sensor of a FX camera, so every single DX lens you purchase will in effect be a complete waste of money when you upgrade to a FX body, unless you want to demote your new FX camera down to a DX camera, which defeats the benefits of the FX body. Your goal, if you want to improve your images, should be to eventually obtain a FX body.

    Second, an FX lens will practically always be sharper on a DX body than ‘any’ DX lens. The reason is because a DX lens on a DX body has the same dispersion of light and coverage of the sensor as a FX lens on a FX body. A lens allows a ‘circle’ of light through the aperture blades that is barely large enough to cover the four corners of the sensor. The dispersion of light and other effects on this circle of light are increased the closer you get to the outer edge of this circle, which is why the four corners of images tend to be less sharp and vignette (darken), especially at small apertures such as f/22 or greater. When you put a FX lens on a DX body, this circle is much wider than the width of the sensor. Since the edges of the projected circle of light coming through a lens is the most soft (less focused/fuzzy) and darker), if you eliminate the darker/fuzzy area from the sensor, you are left with a complete coverage area of near equal sharpness and brightness.

    To refine this, a DX lens is designed to project a circle of light just large enough to cover an approximately 24mm x 16mm sensor, a minimum of the 29mm circle just larger than the diagonal width of the sensor (and therefore the minimum width of the coverage area). The FX lens on the other hand covers a 36mm x 24mm sensor, a minimum of the 43mm circle just larger than the diagonal width of the sensor.

    So a typical DX lens will project around 25mm +/- circle on a 24mm diagonal sensor, causing vignetting and loss of sharpness at the four corners that are close to the edge of the circle of light. Now, instead, project a 43mm circle over a 24mm diagonal sensor and voila, the vignette danger area and degradation of focus around the edge of the circle of light is now far beyond the corners of the sensor’s corners completely eliminating any chance of it reaching the sensor.

    This larger circle of light from the FX lens being projected on a DX sensor is where you get the Nikon x1.5 or Canon x1.6 focal length multiplier because you are only recording a smaller portion of the circle of light from a FX lens on the DX sensor, which effectively covers a smaller area, which would be replicated with a FX lens by ‘zooming’ in to cover the smaller area as viewed/recorded by the DX camera.

    The problem with a DX sensor is that it is smaller than a FX sensor. This means that a DX sensor can only record 66.66% (Nikon) or 62.5% (Canon) of the amount of light of a FX sensor for the equivalent amount of time for an equivalently sensitive set of pixels. Less light recorded means lower quality and less resolution! Keeping this in mind, this is why professional shoot with FX cameras instead of DX cameras, especially when we need to shoot in low light conditions and/or need high resolution images. So, my suggestion is that your goal is to eventually ‘upgrade’ to a FX body if you want/need to in order to take better images for a myriad of reasons, both technical and aesthetic.

    DX bodies are always being improved, but each improved DX body is usually an off-shoot of a new FX body and FX technology, so each time a new and exciting DX camera comes out you are inevitably passing up a FAR greater FX camera, albeit more expensive in most cases, but still far better.

    We always, ALWAYS, suggest you purchase a FX lens, NOT a DX lens. When you eventually purchase a FX body, you’ll throw your DX only lens in a box and cringe over the money you ‘lost’ and ‘wasted’ because some uneducated person convinced you to purchase one. The creation of DX lenses was nothing more than a gimmick and scam to sell ‘more’ lenses at a cheaper price to people who had invested in cheaper starter camera kits. And keep in mind, when you put a DX lens on a modern FX body, your FX camera steps down to a DX sensor area, taking the smaller DX shots with all of the same problems (vignetting and loss of sharpness at the edges at some apertures) as all of the existing DX cameras. It’s like putting a four cylinder engine in a formula one race car.

    Hopefully this post hasn’t overwhelmed anyone, but I feel that this article truly required something of merit instead of the misinformation detailed in it along with no actual usable content.

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