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Difference in magnification

 
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clarnibass



Joined: 10 Jun 2016
Posts: 75

PostPosted: Tue Jun 21, 2016 5:14 am    Post subject: Difference in magnification Reply with quote

Hi

I'm wondering if anyone happens to know this or has a link to info that could save me the time testing this?

The lenses and accessories are:
- 105mm macro lens max magnification 1:1
- 55m macro lens macro lens max magnification 1:2 (1:1 with extension tube)
- Up to 148mm length of extension tubes

I hope to find what (approximate) magnification each setup would give and which would have higher magnification.

Possible setups are:
- 105mm lens with all extensions
- 55mm lens with all extensions
- Reversed 55mm with all extensions
- 105mm with all extensions and reversed 55mm

I also assume that for the reversed lens setups extension tubes would still give a higher magnification but I could be wrong.

I'm used to macro with extension tubes but new to reversing lenses.

Thanks!
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mjkzz



Joined: 01 Jul 2015
Posts: 1151
Location: California/Shenzhen

PostPosted: Tue Jun 21, 2016 9:14 am    Post subject: Reply with quote

I think you can try to work it out yourself by using calculators here:

http://extreme-macro.co.uk/calculators/


Peter
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clarnibass



Joined: 10 Jun 2016
Posts: 75

PostPosted: Tue Jun 21, 2016 8:04 pm    Post subject: Reply with quote

Exactly what I was looking for, thank you.
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clarnibass



Joined: 10 Jun 2016
Posts: 75

PostPosted: Wed Jun 22, 2016 12:30 am    Post subject: Reply with quote

I looked at those calculated and they answer almost everything I wanted to know.

There's one thing I can't find yet and maybe someone would know? When mounting a reversed lens over another lens, does it matter if the first lens is macro? I know that the longer FL of the first lens, the higher the magnification. I have a 105mm macro lens and a 300mm non-macro lens. Would the 300mm still allow higher magnification in this case even though the 105mm is macro? The former has a max mag of about 1:4.
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rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 20097
Location: Richland, Washington State, USA

PostPosted: Wed Jun 22, 2016 10:35 am    Post subject: Reply with quote

Quote:
When mounting a reversed lens over another lens, does it matter if the first lens is macro?

When the rear lens is focused at infinity, magnification depends only on the focal lengths. It does not matter if the lens labels happen to say "macro".

If you focus the rear lens closer than infinity, then life gets more complicated. In that case, magnification depends on the spacing between lenses. Again it doesn't matter whether a lens is labeled macro, per se.

But lenses that are labeled "macro" do tend to be thicker, with more space between the front and rear elements.

That extra space affects the interaction when the rear lens is focused closer than infinity.

The extra space also makes the combo more likely to vignette, even in the simple case where the rear lens is focused at infinity.

There are some other interesting and confusing aspects to lens combos. See the FAQ: Stopping down a lens combo.

If you're getting the idea that lens combos -- short reversed in front of long -- are complicated and difficult to predict, then I think you're on the right path. For more discussion of this aspect, see http://www.photomacrography.net/forum/viewtopic.php?p=52311#52311. (That's post #9 in the aforementioned FAQ.)

Reversing a lens on empty extension, like tubes or bellows, is much simpler to understand and more likely to work OK with randomly selected lenses.

--Rik
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