GH4 Purple Circle on Center of My Image

C

conraddmb118

Member
Hi all,

I just got a Sigma 150-600 Sports telephoto lens to go with my GH4. I use the Aputure DEC LensRegain as a speedbooster. So far, everything was working wonderfully until I was shooting in strong sunlight today and was getting varying degrees of a really nasty purple circle in the middle of my image at any focal length. It's a new lens, so I have only played around with it a little, but on previous shoots, I don't remember having this problem. I'm not sure if it's a direct sunlight issue with the lens, or speedbooster, or something else. I tried to do some research, but I didn't find many others with the same or similar issue.

You can see the rabbit image does not have the circle, but the rocks/ocean one does:

nocircle.jpgpurplecircle.jpg

Thanks!
 
Try the second shot again (shooting into the sun with a dark image like the rocks) with and without a flag. It's probably the sun bouncing around inside the optics. If you have a hood, it may not be adequate.
 
Paul,
Thanks so much for the thoughts. I'll go out and try again, but in the mean time, here are a few other examples from today on the water, and also just now in my room using a fluorescent ceiling light test. They're all at a bit different angle from the light source. All the shots here (except the rabbit one ironically) were using the large metal hood that came with the lens. I would just be surprised if this were a standard lens flare that occurs with all of these lenses, as it got pretty great reviews and none of them noted such a problem that occurs right in the middle of the shot... it just makes the footage unusable. Considering it's a lens built for sports and wildlife (ie strong sunlight), it would be a huge bummer if this were a problem across all lenses. Thanks again, Paul.ceiling.jpgDIFFERENTANGLE.jpgfluolight.jpg
 
Did the first one in the second batch have a bright light source? It seems only the ones with a bright source facing the lens has an issue. How about taking off the speedbooster? Do you have a non-booster adapter?

The fluorescent one does seem to indicate it is something besides regular lens flare. Is the booster optics clean? Maybe some oil got on it? How about the sensor protector?

If the spots are only there when a bright light is facing the lens, then I would play with a flag and see if you can get it to go away. Also, try a shot with the fluorescent and then keep shooting lower and lower away from the florescent and see if it goes away. That would indicate it is something to do the the bright light source.
 
That's exactly what those cheap speedbooster copies do (inferior optics). They're usually fine when you're wide open, but as soon as you stop down and shoot in a bit contrasty lighting situation, you get a purple dot/flare. Try shooting with and without the booster to see it for yourself.
Had a RJSpeedbooster myself but sold it because of that issue. Supposedly new generation of SOME cheap boosters (i.e. Lens Turbo II) minimized the issue, but it's hard to get a proper evidence of that.
 
not sure what cause ur problems but if its the speedbooster problem, usually its because it had internal reflections.
I am using a cheap one on my a7s too, it cause massive flares everywhere when pointed to a light source.

i fixed it by using some fabric covering all the internal wall, now it does the jobs fine.

hope this helps :)
 
It is the booster, the only reason to use it with a tele lens is to gain some light. Otherwise the smaller sensor gives "increased reach" on a tele.

Also as mentioned, internal flare is often very high with these boosters and other lensless adapters so putting some flocking inside is always a good idea.
 
Indeed, the problem with a cheap adapter is that they use the same paint on the inside as the outside. That nice sheen paint you see on the outside causes havoc on the inside. It's like they installed a black diffused mirror inside. I had this problem with a Fotodiox adapter.
 
The lens you are using is very long for a GH4 camera. ( with the Aputure adapter you're using a 105-420mm lens, or 210-840mm FF equivalent )

I would try a quick test using black poster-board ( black cardboard ) where you extend the lens-hood with the cardboard as far as you can without vignetting the edges of your frame, and then try shooting into the sun and see if the purple spot still shows up. With any luck this might cure the problem.
 
Thanks everybody. Those are all great options to try out, and from the chorus about the speedbooster, that this may be my issue. In truth, I was really interested in this lens on the GH4 because of the long reach, as I am trying to film whales from cliffs in Big Sur. I had hope the wireless follow focus/speedbooster would be killing two birds with one stone, as I use it on my Ronin with smaller lenses. It was nearly 600 bucks, which is around the price point for the Metabones XL. I wonder if the metabones would have this issue too? I could always rent one and try it out I suppose. I'll try all of those suggestions and report back with images. I am unfamiliar with what you mean by placing fabric or flocking on the inside of the booster? Could you expand on that? Again, thanks everybody! I am pretty new to this forum, and it's really amazing to see everybody so willing to help out. Cheers.
 
This is what you need for whales at Big Sur. This is a box lens I adapted to MFT. It is a Canon 18-1000mm f/2.8 parfocal lens (that zoom range is not a typo). It only weighs 40 lbs. The front element is 8" across. :). This is what I needed the Fotodiox adapter for. I had to re-spray the inside with flat-black paint. I've posted this a few times. But this rig cracks me up; it's so ridiculously hard to use.

 
conraddmb118 said:
Thanks everybody. Those are all great options to try out, and from the chorus about the speedbooster, that this may be my issue. In truth, I was really interested in this lens on the GH4 because of the long reach, as I am trying to film whales from cliffs in Big Sur. I had hope the wireless follow focus/speedbooster would be killing two birds with one stone, as I use it on my Ronin with smaller lenses. It was nearly 600 bucks, which is around the price point for the Metabones XL. I wonder if the metabones would have this issue too? I could always rent one and try it out I suppose. I'll try all of those suggestions and report back with images. I am unfamiliar with what you mean by placing fabric or flocking on the inside of the booster? Could you expand on that? Again, thanks everybody! I am pretty new to this forum, and it's really amazing to see everybody so willing to help out. Cheers.
Click to expand...

For this subject matter I would opt for a Phantom 4 Pro and learn to fly.
 
Ah, that's amazing Paul! I'm not quite that handy, and unfortunately whale filming requires the ability to run from spot to spot along the coast, so I'm not sure I could manage something like that.:)
Mark, I would absolutely use my Phantom 3 Pro, if I could! The Monterey National Marine Sanctuary doesn't allow flying from 0-5 miles offshore all along Big Sur... Probably for good reason, especially because a lot of marine mammals use the coast line for hauling out/mating/giving birth, so a bunch of loud bees nests hovering above them could be a nuisance--Inside the bay, though, it is allowed and it's on my list of goals for sure!

Thanks Bern, I'll make sure if I move over to metabones that I get the T adapter.
 
Just get a plain tube adapter for the lens (no booster function) because it increases your "reach" and should remove the purple spot too. They are far cheaper than booster types of adapters.
 
Greg_E said:
Just get a plain tube adapter for the lens (no booster function) because it increases your "reach" and should remove the purple spot too. They are far cheaper than booster types of adapters.
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For this use, I agree. A simple mechanical adapter should work well.
 
I'd still flock the inside though, the material is cheap and can be cut with scissors and applied at home. There is a telescope website that sells this stuff and it was cheap to buy a lifetime supply (like $25). It made a big difference on one of my cheapo tube adapters that was poorly designed, lowered flare a lot.

Somewhere in one of my posts I put a link to the stuff I bought, don't have the link handy right now.
 
Greg_E said:
Just get a plain tube adapter for the lens (no booster function) because it increases your "reach" and should remove the purple spot too. They are far cheaper than booster types of adapters.
Click to expand...

I have one, Greg, but the trouble is there is no aperture control right? The lens I have is electronic aperture only unfortunately.
 
I think there are a couple other brands that have the electronics for your lens in a straight tube adapter.
 
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