Olympus in-camera focus bracketing with 10x inf objective

[Lou Jost]

Yes, if the camera is focused at infinity it has nowhere to go. Focus bracketing always goes from near to far. On my PEN F, focus bracketing works even in MF, untethered. That's how I always use it. I am not sure what else might cause it not to run. Maybe you need to set it for multiple shots in the shutter options menu?

As I've mentioned before, the 100-300mm lens vignettes badly.

You are probably right about the need for closer adherence to the rules when NA=0.40

[zzffnn]

Thanks again, Lou.

I just tried it again with MF focus bkt, without infinity microscope objective on. It works now, consistently. I probably did not focus the lenses correctly when I tried it last time. Sorry for my brain cramp

I still like to know how much to back away from infinity, when starting focus bracketing though. 8 turns of focus ring (don't know if that is the same as 8 clicks of Jean-Marc's "<<<" button)? Or maybe focus to a closer item XYZ meters away? Does that matter much for 4x NA 0.10 infinity objective? Probably yes for 10x NA 0.25 objective?

[Lou Jost]

I can't tell you that, you'll have to try it yourself. For low m and a normal (non-macro) lens, I have no problems starting at the closest focus setting. But for high NA objectives (which i have not used with focus bracketing) I agree with you that you probably should be more conservative. But the answer will depend on your lens, your final use of the image (web size, billboard size, etc) so you'll have to test that for yourself. Let us know the results.

[zzffnn]

Lou,

When I put my AO Spencer infinity 4x on my Panasonic 100-300mm, it did not seem to vignette after 160mm or 200mm (cannot remember which).

But I did not have proper ring adapter and there was some light leakage around the objective base, causing square shaped light reflection/artifacts after 160mm or 200mm. Maybe that complicated things a bit.

I will report back once I have proper adapters. I would still be happy, if 4x on P100-300 produces less vignetting, than on my Oly kit zoom 40-150 (which has slight but visible vignetting at 150mm).

Maybe your Mitu 7.5x produces a smaller light cone than my AO 4x? Just guessing. I will confirm it soon.

[Lou Jost]

I am glad to hear that. Maybe the 100-300 isn't as useless as it seemed. But my 7.5x Mitu is known for having a bigger image cone than most objectives. Maybe I should double-check my previous observations.

[jojm]

I don't see that "<<<" or ">>>" button on my camera. So I cannot do 8x "<<<", as Jean-Marc did. I would like to focus to a closer subject, say at XYZ meters away. But how do I determine that XYZ value?

These buttons are on the Olympus Capture software, not on the camera.
Before using this software, my first operating mode was by action on the MF ring on the zoom.
When you put it in MF mode a focus distance scale appears.
By experimentation, I find that slices between the "10 ft" graduation and infinity gave me rather good results. These slices was 1,5x deeper than those I now use with the software.


Unfortunately for you, I think that none of your objectives have focus scale when you use them with MF mode.
This is also a big difference between the Olympus macro 60mm and the 30mm and explains why I always give advice to buy the 60 mm as he got a focus scale on it.

[zzffnn]

Thank you very much, Jean-Marc. You are very kind and helpful.

I will go with your 10 feet focus distance.

I am guessing I can put an resolution target at 10 feet away and manually focus my lens on that?

[zzffnn]

I noticed that focus points (on manual focus wheel) for infinity and 10 feet floated a bit almost every time I changed focus manually, with my Oly kit zoom 40-150mm F/4.0-5.6 and Panasonic 100-300mm F/4.0-5.6.

That did not change, after I turned off in-body stabilization, face recognition and lens stabilization of P100-300 (Oly 40-150 has none).

On the manual focus wheel though, relative distance between infinity and 10 feet seemed somewhat constant.

Maybe that is why those two lenses do not have marks for infinity or 10 feet (because those points drift and rarely reside stably)?

Their manual focus wheels do not stop at infinity either.

[Lou Jost]

Some focus-by-wire lenses are sensitive to the speed at which you turn the focus collar!

[zzffnn]

Thank you, Lou.

I just read about that too and it may explains it.

It is indeed nice to have a focus scale / distance marks. But that Oly 40-150 pro is $1000 USD used Is there another not-so-expensive auto m4/3 tele that works well as tube lens and has distance marks?

[Lou Jost]

Not that I know of...

[zzffnn]

Indeed, I was able to consistently return to the same focus points (infinity vs 10 feet), by turning the manual focus wheel VERY slowly.

With my Oly 40-150 kit zoom, it was smooth and took almost one full turn.

With my Panasonic 100-400 zoom, damping was too high and it took a little more than two turns and quite a long time.

I feel like I need to practise Yoga for this.........

[zzffnn]

Jean-Marc,

For a 4x NA 0.10 infinity objective, what step size do you use? Do you also use 10 feet focus point as start point for focus bracketing, or do you use a different focus start point?

Thank you very much,
Fan

[jojm]

Fan,
It's now quite a long time since the last time I used the Nikon 4x.
I have to check one more time before my answer, it will take a couple of days.

[zzffnn]

No rush at all, thank you very much, Jean-Marc!