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Archive 2013 · Flare spot (hot spot) with Mamiya 120/4
  
 
JohnJ
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p.2 #1 · p.2 #1 · Flare spot (hot spot) with Mamiya 120/4


RustyBug wrote:
Mine was definitely spot flare from internal reflection.

I was able to reduce it somewhat with some flocking material, but due to certain design issues, I couldn't get the flocking to contend with it fully. BTW ... mine was a shift capable adapter. I replaced it with my Fotodiox Pro ... no more issues (but no movements either).

Obviously the Mirex has its value in its movements ... wondering if there's any flare that might be kicking up off a "wear spot" that needs some touch up.



I thought I'd try the Mamiya 35/3.5 N with the Mirex to see if I too had any flare spot. This gif shows the lens at F22 and focused at varying distances in feet, eg 1.5', 2', etc to -infinity. I didn't see any flare spot. I also tried F8 and also no flare spot.







The test image is just back lit piece of paper to give an even tone.



Jan 13, 2013 at 11:24 AM
JohnJ
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p.2 #2 · p.2 #2 · Flare spot (hot spot) with Mamiya 120/4


LightShow wrote:
I would try some different settings(focus distance and light placement) to see if they have an effect on size or intensity.


Yeah, I had every intention, as per below.

The images below are with the lens set at varying magnification ratios as stated on the lens, eg 1:1 through to infinity. In this test the flare spot is only visible at approx 1:3 which happens to be exactly where I was shooting the previous test images with the black lens, ie the original post.







The images below are the same test as above but with finer resolution in the lower magnification range. The flare spot varies in intensity at various ratios, not just 1:3.







The above 2 gifs have had contrast cranked up, by adjusting black and white point, to exaggerate the flare spot and make it more visible. The images are of a light box, ie an even toned surface. It's hard to see the flare spot without the contrast adjustment unless the image happens to show it, such as the first examples with the black lens against a white background.



Jan 13, 2013 at 11:32 AM
AhamB
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p.2 #3 · p.2 #3 · Flare spot (hot spot) with Mamiya 120/4


JohnJ wrote:
I thought I'd try the Mamiya 35/3.5 N with the Mirex to see if I too had any flare spot. This gif shows the lens at F22 and focused at varying distances in feet, eg 1.5', 2', etc to -infinity. I didn't see any flare spot. I also tried F8 and also no flare spot.


I wouldn't expect it in a 35mm lens because their lens design is so different. In fact I've only seen/heard of it in macro lenses. Even the Coastal Optics 60/4 has it at a certain magnification with small apertures. Maybe you could trigger it with the 35/3.5 if you put it on tubes but I'd imagine that the aperture spot would be much smaller (it's my feeling that the size of the hotspot is a function of the focal length, could be wrong though).



Jan 13, 2013 at 05:09 PM
Toothwalker
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p.2 #4 · p.2 #4 · Flare spot (hot spot) with Mamiya 120/4


mcbroomf wrote:
I believe this is internal flare caused because sensors are more reflective than film surfaces. Modern lenses have better coatings on the back lens surface to take care of this. The excellent Tamron Adaptall 2 SP 90/2.5 is well known for this, but also only at small apertures. I use it on Nex bodies and keep to F11 and wider and never see it.
Mike


Sensors are not more reflective than film, and the improved coating on the rear lens surface for digital is marketing claptrap.

AhamB wrote:
I remember reading that the rear element of the Tamron is nearly flat, which would the reason why the reflection off the sensor is reflected back onto itself again by the lens. I don't know if the 52BB version simply has improved coatings on the rear element or an actually differently shaped rear element. It would be interesting to find out.


Even if this rear element would contribute to the flare formation, it would be reflecting light from a spot in the image center which is not supposed to be there in the first place. Something already went wrong elsewhere.

It looks as if the light intensity of the flare on the sensor is constant, independent of the aperture, whereas the intensity of the image decreases with decreasing aperture. The size of the flare patch precisely matches the lens aperture, so it becomes smaller as the lens is stopped down and brighter relative to the intended image. Hence it becomes noticed at small apertures.

I think we need at least one reflector in front of the aperture to explain the observations.





Jan 13, 2013 at 05:16 PM
RustyBug
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p.2 #5 · p.2 #5 · Flare spot (hot spot) with Mamiya 120/4


My 150/2.8 A was very noticeable as I stopped down. With the 35/3.5 N significantly less (errantly sold due to adapter infinity issue ) noticeable. Changed adapter (after selling 35/3.5 N) and it went away on the 150/2.8 A, but no longer had the 35/3.5 N to compare with.



Jan 13, 2013 at 05:41 PM
jcolwell
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p.2 #6 · p.2 #6 · Flare spot (hot spot) with Mamiya 120/4


Toothwalker wrote:
Sensors are not more reflective than film, and the improved coating on the rear lens surface for digital is marketing claptrap.


Agreed. That's why my great old Pentax LX was able to meter flash intensity from its reflection off the film surface. Modern DSLR cannot do this, and so require "pre-flash" to determine what's required.

OTOH, "improved" coating on any elements is always welcome, as long as it's 'real'.




Jan 13, 2013 at 06:29 PM
JohnJ
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p.2 #7 · p.2 #7 · Flare spot (hot spot) with Mamiya 120/4


RustyBug wrote:
My 150/2.8 A was very noticeable as I stopped down. With the 35/3.5 N significantly less (errantly sold due to adapter infinity issue ) noticeable. Changed adapter (after selling 35/3.5 N) and it went away on the 150/2.8 A, but no longer had the 35/3.5 N to compare with.


Kent, I've just tried the 150/2.8 (with Mirex) in case that showed any flare spot but I saw no sign at all. I tried it through the entire focus range. Which camera/adapter where you using when you had an issue with it?



Jan 14, 2013 at 11:49 AM
 

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RustyBug
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p.2 #8 · p.2 #8 · Flare spot (hot spot) with Mamiya 120/4


I was using an Arax shift adapter. It had a specific design issue in the shift mechanism that was the source of internal reflection. I was able to temporarily flock it to confirm it as the source, but I never achieved a permanent solution. Since I had gotten the shift adapter it to coincide with my 35/3.5 N for pano shifting, I didn't pursue it further (having already sold my 35/3.5 N). I now have the Canon 24L TS-E II.

Since getting my Fotodiox Pro adapter (no shift/no tilt) I have not experienced any issues as before. Thus, mine was inherent to the adapter, not the glass. I can't speak to the 120/4 directly, just thinking that with the moving parts of the Mirex, there might be a small spot on it that has become "polished" or "exposed" to be more reflective than it originally was.

Edited on Jan 14, 2013 at 04:54 PM · View previous versions



Jan 14, 2013 at 04:49 PM
Toothwalker
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p.2 #9 · p.2 #9 · Flare spot (hot spot) with Mamiya 120/4


jcolwell wrote:
Agreed. That's why my great old Pentax LX was able to meter flash intensity from its reflection off the film surface. Modern DSLR cannot do this, and so require "pre-flash" to determine what's required.

OTOH, "improved" coating on any elements is always welcome, as long as it's 'real'.


Agreed. Improved coatings are always welcome, on any element.




Jan 14, 2013 at 04:51 PM
phuang3
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p.2 #10 · p.2 #10 · Flare spot (hot spot) with Mamiya 120/4


I've come across a few flare spots with various lenses. A pox on them. Found this flare spot with the Mamiya A 120/4, on a 5D2 with Mirex adapter. The flare spot, or hot spot, can bee seen fairly clearly in the gifs below. This might depend on magnification too. Note that this test was a high contrast scenario where the black subject is on a white background, a situation likely to provoke flare.

I'd say this is a common problem when you shoot your subject with strong background lighting. (In your picture, it's possible from the bottom) I usually use black cardboard to cover out of frame area.


Edited on Jan 21, 2013 at 05:42 AM · View previous versions



Jan 18, 2013 at 06:47 AM
JohnJ
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p.2 #11 · p.2 #11 · Flare spot (hot spot) with Mamiya 120/4


phuang3 wrote:
I'd say this is a common problem when you shoot your subject with strong background lighting. (In your picture, it's possibly from the bottom) I usually use black cardboard to cover out of frame area.


It's not a problem which is induced by the environment, lighting etc although these can certainly compound flare if a lens is prone to it. I use a Meogon 80/2.8 which has a significant flare spot but I like to use it so I've found that I can reduce, not eliminate, the flare spot with a large hood.

A flare spot will appear when you shoot a grey card if a lens is prone to it, it just won't be dramatically obvious.



Jan 19, 2013 at 06:25 AM
SoulNibbler
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p.2 #12 · p.2 #12 · Flare spot (hot spot) with Mamiya 120/4


Also it should be mentioned that the rear element of the 120/4 is HUGE. Much bigger than the window in the MIREX. I think this is probably the cause but I can try to duplicate your results tonight when I'm near a flash or tripod.


Jan 23, 2013 at 11:48 AM
JohnJ
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p.2 #13 · p.2 #13 · Flare spot (hot spot) with Mamiya 120/4


SoulNibbler wrote:
Also it should be mentioned that the rear element of the 120/4 is HUGE. Much bigger than the window in the MIREX...


Yes, the 120/4 rear element is very large, but so is the Mamiya 80/1.9. I've just tried the flare spot test on the 80/1.9 with no hint of a flare spot or hot spot to be found across the entire focus range.

SoulNibbler wrote:
... I think this is probably the cause but ...


I don't think the Mirex has anything to do with the flare spot on the Mamiya 120/4 although it might be causing other optical issues (such as vignetting) as the aperture in the Mirex does seem too small for a lens like the 120/4 or 80/1.9.

I If I had another adapter I would have tried it long ago but I'm fairly confident that shooting a blank wall, a grey card or clear sky with the 120/4 at F32 and focused to the 1:3 ratio (approx 0.6 metres) will show a flare spot regardless of the adapter used.



Jan 24, 2013 at 11:05 AM
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