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Author Topic: Sigma 150 Macro Something I've never seen before  (Read 13739 times)

Cinto

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Sigma 150 Macro Something I've never seen before
« on: October 09, 2014, 07:25:06 PM »
A reflection of the diaphragm blades. 5D2, off camera flash.

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Sigma 150 Macro Something I've never seen before
« on: October 09, 2014, 07:25:06 PM »

pdirestajr

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Re: Sigma 150 Macro Something I've never seen before
« Reply #1 on: October 09, 2014, 07:57:25 PM »
Wow! That actually looks really cool though!

ajfotofilmagem

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Re: Sigma 150 Macro Something I've never seen before
« Reply #2 on: October 09, 2014, 08:23:31 PM »
It seems a lack of synchronization between the exact moment the shutter opens and closes the diaphragm (stopped down). Difficult to identify the cause of the problem. But it would be very strange to anticipate the diaphragm, and it seems more plausible that the camera shutter had delayed it.

risc32

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Re: Sigma 150 Macro Something I've never seen before
« Reply #3 on: October 09, 2014, 08:40:00 PM »
weird. were you using some sort of filter? the spider wasn't behind glass? weird, and cool. not that i'd want that on all my shots or anything...

ajfotofilmagem

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Re: Sigma 150 Macro Something I've never seen before
« Reply #4 on: October 09, 2014, 08:51:34 PM »
I imagined another possibility. If the mirror does not respect the right moment to go up and down, could reflect the sunlight entering through the optical viewfinder, and that light reaches the diaphragm of the lens backwards.
« Last Edit: October 09, 2014, 08:53:39 PM by ajfotofilmagem »

Canon1

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Re: Sigma 150 Macro Something I've never seen before
« Reply #5 on: October 09, 2014, 09:08:23 PM »
It looks like a reflection off of a pane of glass.  Were you shooting through a window at this spider?

chromophore

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Re: Sigma 150 Macro Something I've never seen before
« Reply #6 on: October 09, 2014, 09:45:07 PM »
To be able to see the diaphragm in the image, there must be an optically flat surface in front of the lens, such as a filter.  If this flat surface is sufficiently close to the subject in focus, and the lens is stopped down, then the reflection of the diaphragm can be within the depth of field, and will appear in the image, especially if there is enough incoming light to the lens that it bounces off the diaphragm (such as if an off-camera flash is pointed at the lens).

Without a flat surface from which a reflection of the lens' interior can be seen, such a phenomenon cannot occur because any internal reflections off the glass-air interfaces on individual elements would not be image-forming.

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Re: Sigma 150 Macro Something I've never seen before
« Reply #6 on: October 09, 2014, 09:45:07 PM »

Cinto

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Re: Sigma 150 Macro Something I've never seen before
« Reply #7 on: October 09, 2014, 10:14:05 PM »
Sorry i was away, I was using an after market flash extension cord, I was around 120th I think and yes I had a B&W pro filter on.
« Last Edit: October 09, 2014, 10:17:03 PM by Cinto »

Cinto

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Re: Sigma 150 Macro Something I've never seen before
« Reply #8 on: October 09, 2014, 10:26:03 PM »
I think its from the flash as Images taken from the exact same place only show it when the veiling flare becomes intense.

chromophore

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Re: Sigma 150 Macro Something I've never seen before
« Reply #9 on: October 09, 2014, 10:47:58 PM »
Sorry i was away, I was using an after market flash extension cord, I was around 120th I think and yes I had a B&W pro filter on.

Hmm, makes me think less of B&W pro filters. Those things should be multicoated to prevent this.

Even the best multicoating won't completely stop this phenomenon.  Think of it this way:  if you can *see* a piece of glass, that necessarily means it reflects some incident light, otherwise it would be completely invisible to you.  To be immune to this phenomenon, you'd need a glass that would look invisible and fail to show any reflected light over a wide range of viewing angles.

The fact that the flash is throwing a ton of light directly into the lens at an angle that is not image-forming virtually guarantees that there will be a lot of veiling glare.  That non-image-forming light bounces off the lens sub-barrel and diaphragm, comes back out, hits the filter, and because it's a macro shot, ends up forming a very nice detailed ghost of the inside of the lens.

TexPhoto

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Re: Sigma 150 Macro Something I've never seen before
« Reply #10 on: October 10, 2014, 01:00:03 AM »
Sorry i was away, I was using an after market flash extension cord, I was around 120th I think and yes I had a B&W pro filter on.

Hmm, makes me think less of B&W pro filters. Those things should be multicoated to prevent this.

Sorry to be obtuse here, but when light hits surface of the glass on both surfaces, there is reflection, and refraction.  But in the glass there is transmission and absorption.  Some light will always be lost to being absorbed.  It makes heat.  So

Even the best multicoating won't completely stop this phenomenon.  Think of it this way:  if you can *see* a piece of glass, that necessarily means it reflects some incident light, otherwise it would be completely invisible to you.  To be immune to this phenomenon, you'd need a glass that would look invisible and fail to show any reflected light over a wide range of viewing angles.

The fact that the flash is throwing a ton of light directly into the lens at an angle that is not image-forming virtually guarantees that there will be a lot of veiling glare.  That non-image-forming light bounces off the lens sub-barrel and diaphragm, comes back out, hits the filter, and because it's a macro shot, ends up forming a very nice detailed ghost of the inside of the lens.

Sure, without doing something more drastic, such a reflection is pretty much guaranteed. I'd love to see a filter like this with a nanocoating. Where multicoating can cancel out enough reflections to allow up to 97% transmission, that's still 3% reflection. A nanocoating, on the other hand, can simply prevent reflections entirely, resulting in 99.95% or better transmission. I bet a nanocoated UV/protect filter would have handled this situation nicely. ;)

Jaccop

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Re: Sigma 150 Macro Something I've never seen before
« Reply #11 on: December 31, 2016, 02:08:44 PM »
Nice sharp lens, only af hunt to much.
Canon 1dx, Canon 7d mark II, sigma 150-600 sport, canon ef 300 mm f4, canon ef 16-40L 4.0, sigma 150 macro 2.8, canon 50 mm 1.8 stm.

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Click

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Re: Sigma 150 Macro Something I've never seen before
« Reply #12 on: December 31, 2016, 02:36:10 PM »
Nice sharp lens, only af hunt to much.

Very nice picture, Jacco.

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Re: Sigma 150 Macro Something I've never seen before
« Reply #12 on: December 31, 2016, 02:36:10 PM »

Jaccop

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Re: Sigma 150 Macro Something I've never seen before
« Reply #13 on: December 31, 2016, 04:22:27 PM »
Thanks, made with 5 d mark iii that i had for a few days
Canon 1dx, Canon 7d mark II, sigma 150-600 sport, canon ef 300 mm f4, canon ef 16-40L 4.0, sigma 150 macro 2.8, canon 50 mm 1.8 stm.

Flickr.  https://www.flickr.com/photos/91447801@N03/31789925305/

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Re: Sigma 150 Macro Something I've never seen before
« Reply #13 on: December 31, 2016, 04:22:27 PM »