Sony Alpha 1, SEL 200-600 or Canon R5, RF 100-500

Started 4 months ago | Discussions thread
daran Contributing Member • Posts: 595
Re: Sony Alpha 1, SEL 200-600 or Canon R5, RF 100-500

win10-64 wrote:

Is there a easy way to find out whether a 200-600mm is a good copy or not.

The usual way is to do a four corner comparison, see various variants of the same test idea:

The test has the advantage that it is comparatively easy to do, without requiring highly precise anything. Almost foolproof. It will tell you whether your copy is reasonably straight, which covers the majority of issues. Bear in mind that this is all analog tech and there is no perfect copy.

If you are particularly nerdy, or really wana make sure, there are other tests:

* a static scene that you can use across time and all your lenses, e.g. an indoor brick wall or (my case) a hallway with Siemens-stars and some feathers or hair; flash light the scene to be repeatable; be very careful about being orthogonal; use tripod and timer or remote

* best: use above static scene and compare different copies back to back

* use an artificial star (extremely small light source, 0.05mm or less); you could use distant street lights at night, but you'd need very good seeing and it would not be repeatable; check whether the star focuses to a single pixel when centered (beware of the star-eater, no long exposures); check whether the de-focused light spot is round when centered; check whether the de-focused light spot has symmetric shape when comparing corners

Is the difference between a good copy and bad copy more noticable the further the subject is away or even at close distances?

Typically no. If there is any slanted or shifted lens in the assembly, it would affect all focus distances and all focal lengths of a zoom at least to some degree.

I have wondered whether mine is a good copy when wide open, but hopefully it is more a DOF issue and needing the focus point to be more precise on the head and eye with such a shallow DOF especially with the TC 1.4 on.

So far I was content with any lens that "passed" the four corner test. See roger-cicala for why that is no suprise:

 daran's gear list:daran's gear list
Sony a1 Sony FE 90mm F2.8 macro Sony FE 135mm F1.8 GM Sony FE 200-600 F5.6-6.3 Sony FE 35mm F2.8 +5 more
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