a7rMk4/FE 200-600mm sharpness help

Started 2 months ago | Questions thread
Michael Fritzen Veteran Member • Posts: 6,371
Re: a7rMk4/FE 200-600mm sharpness help
2

Glenn Barber wrote:

There have been numerous postings of focus frustration with the A7R4 and the 200-600. Sony even did some research on this internally . Some well know pro's have also noted this frequently. It might be sample variation, but sometimes it just doesn't lock down the focus quite right. I have lots of examples where the focus is just slightly off or it seemed blurred when it should not. Waviness is atmospheric - uniform softness is usually not.

Here are some suggestions to help spot where the issue might be.

1. Take off all filters and retest

2. Shoot on a solid tripod with exposure delay to eliminate vibration

3. Use much higher shutter speeds

4. Turn off IS or change to 2 and see if it makes a difference.

Some have suggested that IS stabilization has something to do with this.

I did see focus accuracy and consistency improve on the A1

All true certainly. But this applies in any case to shooting situations which are not in any way limited by the atmospheric conditions.

When the OP mentions "noise" then we're straight loosing track because noise issues certainly are not related to the performance of the lens mounted on a cam.

What needs to be clear - and new owners of the 200-600 over on the Sony E-Mount APS-C forum face similar difficulties - is that photographing in the long telephoto range runs into some challenges which are the less relevant the shorter the FL one's working with: it's about the "package of air" between the photographer and the subject and what it contains / what happens. It's summer in the northern hemisphere and when we can see with the naked eye already the heat oscillating (and which doesn't do any good for our perception of detail) and if we look a bit more conscient, how much dust there's airborne, how many insects fly around then we're on the way to get a notion of what "bad" the "enlarging", the compression of that view by the long FL does. Let's think about a landscape shot: the best we'd get is an almost aquarell looking image with perhaps some black dots - insects caught in flight.

IAW it's a misconception for the use of a long FL lens to shoot over distances longer than a "few" meters to get high detail resolution on the subject. In cool clear atmospheric conditions the range extends a bit but even then it's not the main purpose for such a lens and the lack of detail gets the more noticeable the longer the distance.

Based on this, any lens testing makes only sense when the mentioned circumstances are considered and under control. If not, it's only time wasted by testing and showing off that a lens didn't well in a situation when it's clear that it couldn't perform. Then it's not "testing a lens" but (one more) confirmation only that atmospheric conditions matter (and have to be taken into account).

Now if you want to test your lens for any possible optical flaws then it's better to place a fine detailled target on a wall, perhaps about 10-15m away and take some test shots - best using a tripod but could be also freehand if the exposure time is short enough - and then analize the detail rendition.

On a side note perhaps it's worth to do some inquiry about paparazzi shots of some people of the world of rich and famous. There were shots taken with exotic and extremely expensive lenses like a Minolta MD Mirror f/16-1,600mm (a jaw dropping piece of optics which I saw once at the Cologne Photokina show) . But the depicted persons were hardly recognizeable because of the lack of detail - and the reason was not the flawed optics, the grainy film, it was simply the toll to be paid to the atmospheric disturbances over the long distance. No miracles since.... However, I think the photographer who took such a shot was pretty well paid....

HTH.

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Cheers,
Michael Fritzen

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