Who steps down?

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geetee50
Posts: 91
Joined: Tue Mar 06, 2012 1:23 pm

Who steps down?

Post by geetee50 »

Hi, I seen a few posts on Flickr regarding people stepping down their last shot in a set for stacking to gain a smoother transition to OOF, When working with such a fine area of focus like a plan apo are there any real noticeable benefits to stepping down?


Here is the iris adapter for the Mitz or BD objective

http://www.ebay.co.uk/itm/200619040662? ... 1423.l2648

Can anyone with this adapter or similar show two single shots of its effect on the dof.

Thanks Gary

Harold Gough
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Post by Harold Gough »

Gary,

Is this what you mean? (My circumstances were a particular need rather than planned).

This was one of my very first stacking attempts:

http://www.photomacrography.net/forum/v ... 2048#82048

Harold
My images are a medium for sharing some of my experiences: they are not me.

enricosavazzi
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Re: Who steps down?

Post by enricosavazzi »

geetee50 wrote:...
Here is the iris adapter for the Mitz or BD objective

http://www.ebay.co.uk/itm/200619040662? ... 1423.l2648
...
Just to avoid potential confusion, the eBay ad is only for the Mitutoyo to M42 adapter. The picture shows the adapter mounted on a diaphragm which is available as a separate item from the same seller.
--ES

geetee50
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Joined: Tue Mar 06, 2012 1:23 pm

Post by geetee50 »

Thanks Harold the question relates to 5x and above, Enricosavazzi the sample link was to show the item pictured but thanks for pointing this out, the item in the picture is designed to hold a powerful objective but is it designed to work with one?

Example questions based on Mitutoyo plan apo's

1:
We are shooting at say 5x mag and stepping down the last shot to improve a softer transition to oof, if using an NA of 0.14 we will be at f:3.5 so in theory I can see this working, but if our depth of focus is only 14.0μm is stepping down 2 stops going to improve the transition?

2:
We are now shooting at say 10x mag, with a NA of 0.28 we will be at f:1.8 and our depth of focus is now only 3.5μm is stepping down 2 stops going to improve any transition?

Harold Gough
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Location: Reading, Berkshire, England

Post by Harold Gough »

5x is out of my operating range until I get practice with some old and some new, unused lenses.

Harold
My images are a medium for sharing some of my experiences: they are not me.

Craig Gerard
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Location: Australia

Post by Craig Gerard »

Gary,

There may be some information in this thread relevant to your enquiry.

http://www.photomacrography.net/forum/v ... php?t=9321



Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

seta666
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Re: Who steps down?

Post by seta666 »

geetee50 wrote:Hi, I seen a few posts on Flickr regarding people stepping down their last shot in a set for stacking to gain a smoother transition to OOF, When working with such a fine area of focus like a plan apo are there any real noticeable benefits to stepping down?
I normally step down for the last shot in my 3D subjects, for flat subjects I do not normally do it
Here is the iris adapter for the Mitz or BD objective

http://www.ebay.co.uk/itm/200619040662? ... 1423.l2648

Can anyone with this adapter or similar show two single shots of its effect on the dof.

Thanks Gary
Je, je; I designed that adapter! ;-) I was fed up of trying to find the right one from dissasembled enlarger lenses and seeing jinfinance had Iris for sale I asked him to make a M42 case for it

This is the original post were I anounced it, on the second page there is a test

http://www.photomacrography.net/forum/v ... is&start=0

Regards
Javier

geetee50
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Joined: Tue Mar 06, 2012 1:23 pm

Post by geetee50 »

Superb little iris Javier i think it would be worth the few pounds of investment, works with great effect on 5x. If using with a 10x objective how many shots do you step down to get best effect, i see John Hallmens test showed best results with 4 stopped down IMO. In Craigs link http://www.photomacrography.net/forum/v ... php?t=9321


I've seen that link many moons ago craig, thanks for posting, funny how we forget. I'll put it in a favorites folder this time.

seta666
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Location: Castellon, Spain

Post by seta666 »

It depends, sometimes I stop 2EV sometimes 4EV; sometimes only one las shot stoped down and sometimes I stack a few stopped down shots at the end.

The search tool in the forum works pretty well, I do not use favorites ;-)

regards
Javier

rjlittlefield
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Post by rjlittlefield »

geetee50 wrote:Can anyone with this adapter or similar show two single shots of its effect on the dof.
I think the info you're looking for can be seen HERE, top left versus top right picture. Ignore all the in-focus stuff and just look at the out-of-focus background.
We are now shooting at say 10x mag, with a NA of 0.28 we will be at f:1.8 and our depth of focus is now only 3.5μm is stepping down 2 stops going to improve any transition?
To my eye, the major effect is not the additional ~15 microns of good focus that you get by stopping down.

Instead, it is the appearance of far background, where things are horribly out of focus. In those areas, the added aperture will reduce the blur radius by a factor of 2X at 2 stops and 4X at 4 stops.

That much reduction in blur can make the difference between a completely unrecognizable background and one that's at least suggestive although still very blurred.

--Rik

geetee50
Posts: 91
Joined: Tue Mar 06, 2012 1:23 pm

Post by geetee50 »

Yes I see that one thanks Rik, Makes sense and without seeing it for real i didn't think any blur could be improved with such a fine depth of focus.
That much reduction in blur can make the difference between a completely unrecognisable background and one that's at least suggestive although still very blurred.
I was thinking there was just a gradual blur from sharp to unrecognisable with a iris rather than the hard transition without but the effect of a suggestive shape gives this piece of equipment a place in my box.

thanks guys.

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