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Macro Lenses

Discussion in 'Lens Matters' started by SAW, Feb 8, 2019.

  1. SAW

    SAW Member


    Basic question but what's the difference between a normal lens and a macro one ?

    I do astrophotography and I'm looking for a lens to fit the whole of the Orion constellation in on the crop sensor. The EF-S 24mm would work but it's a little too wide, the EF-S 35mm would probably be better but it's a macro lens so is it still suitable for astrophotography as it's a macro ?

  2. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    Short answer: a matter of opinion.

    Long answer: In theory a macro lens is optimised for very short camera to subject distances and typically has a mount that allows the user to focus down to an object:image size ratio of 1:1. Some lenses such as the Tamron AD2 focussed to 1:2 but came with an extension tube to extend the range to 1:1. Because true macro lenses are designed for very short subject:image distances they may not be as good for astronomical photography as a lens designed for more general use. On the other hand many photographers use true macro lenses for general photography and achieve impressive sharpness.

    Important point: a lot of manufacturers put the word "macro" on lenses that are anything but. You need to do a fair bit of research if you're new to this.
  3. Benchista

    Benchista Which Tyler

    Literally, it means they focus to life size, and they should be optimised for close focus work. In the past, that sometimes meant that they weren't very good at distance, but that's never been the case with the best macro lenses, and is seldom the case these days with any modern macro lens.
    I've no experience with the 35mm EF-S, but I do use the fairly similar 28mm EF-M macro, and that's actually excellent at distance, so I don't see why the 35 EF-S wouldn't be.
  4. PeteRob

    PeteRob Well-Known Member

    The only thing I've noticed about using a macro lens (the Canon 100 mm F2.8 IS) for non-macro photography is that autofocusing can be a bit slower. I think this is because of the lower gearing that allows much more precise positioning of the lens elements. The further away the subject the less noticeable this is.

    The EF-S 35mm, despite the best efforts of the Canon site to not work, appears to be a true macro lens allowing 1:1 reproduction.

    I don't know if either of the EF 35mm lenses would be better for astro-work as their wider image circle may mean better definition at the edge of the crop sensor.
  5. daft_biker

    daft_biker Action Man!

    The macro lens is likely to be sharper at infinity focus. The focus closer bit is less likely to be of use when shooting distant objects.

    Macro lenses of the infinity to life-size variety tend to be sharpest at infinity and then get less sharp as the focus gets closer. I've never used one that didn't behave like that....same with zooms....better at infinity than minimum focus. Suspect it would be a very old lens or something highly specialised if it did something different.
  6. Petrochemist

    Petrochemist Well-Known Member

    Many lenses with macro on them are nothing of the kind. A true macro lens is designed for close focus work and will produce images at least half life size on the sensor.
    Those that are labelled macro but can't manage this are merely close focusing versions, of normal lenses.
    Nearly all macro lenses will focus to infinity without any issues (there are a few like the Canon MP-E 65 that wont focus beyond a few feet)

    At close distances (true) macro lenses will usually be sharper than other lenses that have had extras added to enable closer focusing. Some of these macro lenses are also unusually sharp at infinity, others can be noticeably softer at distances.

    Macro lenses tend to have smaller apertures than normal lenses but they can still be good for astrophotography, not all are by any means.
    In general I wouldn't expect any particular correlation (positive or negative) between a lens being labelled as macro & it's suitability for astro.
  7. Benchista

    Benchista Which Tyler

    The 35mm EF-S certainly is, it goes up to life size, and has a built-in macro light.
  8. Jack D3200

    Jack D3200 Well-Known Member

    The free astro programme, "Stellarium" has a facility where you can enter details of lenses, telescopes etc and it will show you the area covered against any chosen celestial object.
    Learning likes this.

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