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darth mollusk

Canon RF100 (1.4x mag) + UCL

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I've been shooting with the Canon R5 + RF 100 macro. The RF 100 has a minimum working distance of 8.5 cm from the front element – at this distance magnification is 1.4x. I'm considering the addition of a wet close up lens but have some questions: 

1. Would a +10 diopter be the equivalent of +15 or more when in front of a lens that already shoots at 1.4x magnification? 

2. The older EF 100 minimum working distance is reduced from 14.6 to 6.9cm when behind the Inon UCL 90 (+11 diopter). Would the RF 100 minimum working distance then be reduced from 8.5 to 4cm? I would guess that DOF would be razer thin at this distance...

Edit: after writing this I think I've answered my own questions. Seems somewhat obvious now that both statements (1 + 2) should be roughly true. Any recommendations on a sharp +5 or +6 UCL with a reasonable minimum working distance?

Edited by darth mollusk

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1 hour ago, darth mollusk said:

I've been shooting with the Canon R5 + RF 100 macro. The RF 100 has a minimum working distance of 8.5 cm from the front element – at this distance magnification is 1.4x. I'm considering the addition of a wet close up lens but have some questions: 

1. Would a +10 diopter be the equivalent of +15 or more when in front of a lens that already shoots at 1.4x magnification? 

2. The older EF 100 minimum working distance is reduced from 14.6 to 6.9cm when behind the Inon UCL 90 (+11 diopter). Would the RF 100 minimum working distance then be reduced from 8.5 to 4cm? I would guess that DOF would be razer thin at this distance...

Edit: after writing this I think I've answered my own questions. Seems somewhat obvious now that both statements (1 + 2) should be roughly true. Any recommendations on a sharp +5 or +6 UCL with a reasonable minimum working distance?

The RF-100 working distances and magnification with SMC-1 are on the  Nauticam RF port chart,  Working distance is 29-80mm  and 2.3x maximum magnification.  This shows that you only have a relatively a small gap in magnification compared to the main lens.    At min focus no diopter you are 1.4x and 85mm working distance Put the SMC-1 on and at infinity focus you'll have 80mm working distance and you can work down towards 29mm working distance and 2.3x. 

I would expect you would get 1.5x when focused at infinity on the lens approximately with the SMC in place and you can steadily reduce that working distance for more magnification.  This assumes linear increase in magnification with distance it will probably be a little more if there is significant focus breathing in the RF 100mm maybe 1.6-1.7x at a guess.  Depth of field of course is proportional to magnification.

As I recall from other threads the INON UCL-90 is fairly close in magnification and is said to give slightly more working distance.  I would expect similar changes in working distances for the INON UCL-90. The next lens along in INON lineup is the UCL-165 - most of the +5 to +6 diopters seem to be similar 2 element construction.

 

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Thanks Chris – exactly the information I was looking for!

An 80mm working distance for the SMC-1 is amazing. I looked up the EF 100 on the Nauticam port charts and it has a working distance of 53–93mm. Considering that the naked EF lens has a min working distance of 146mm, that leaves room for the use of a weaker UCL in the 93 to 146mm gap.

As there's only a 5mm gap between the RF 100 (85mm) and SMC-1 (80mm) there's no reason to purchase a weaker UCL. This must be unique to the RF 100 lens design as I've not seen any other examples of strong UCL (+11 / 2.3x or equivalent) focusing right up to the 100mm macro lens minimum working distance.

I've also read that the Inon UCL lenses have more working distance than the Nauticam equivalents – though in this case there's not much room to improve.

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6 hours ago, darth mollusk said:

Thanks Chris – exactly the information I was looking for!

An 80mm working distance for the SMC-1 is amazing. I looked up the EF 100 on the Nauticam port charts and it has a working distance of 53–93mm. Considering that the naked EF lens has a min working distance of 146mm, that leaves room for the use of a weaker UCL in the 93 to 146mm gap.

As there's only a 5mm gap between the RF 100 (85mm) and SMC-1 (80mm) there's no reason to purchase a weaker UCL. This must be unique to the RF 100 lens design as I've not seen any other examples of strong UCL (+11 / 2.3x or equivalent) focusing right up to the 100mm macro lens minimum working distance.

I've also read that the Inon UCL lenses have more working distance than the Nauticam equivalents – though in this case there's not much room to improve.

Yes, the distances are quite close, I expect the RF-100 has quite a bit of focus breathing as the magnifications for the 100mm EF and 100mm RF with SMC- 1 are quite close at 2.2 and 2.3x even though the RF lens is 1.4x bare.  The shorter focal length due to focus breathing means that magnification by the diopter is les, but at infinity focus, the focal length is 100mm and the diopter has a larger effect.  This may mean that  there is a small working distance gap but a rather larger magnification gap?  Only way to find out for sure is to take some shots of a ruler.

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That makes sense. Brian Carnathan at 'the digital picture' noted in his review that the RF100 exhibits "moderately strong" breathing. It also exhibits noticeable focus shift when stopping down at close focus distances – this is usually masked by increasing DoF at smaller apertures, but I wonder if it will be a problem with the razor thin DoF even at f22+ when using a UCL... probably.

Like you said, only one way to find out. 

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