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Metabones Speed Booster - Vignetting with Tele-Lenses
- Thread starter khaw
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- sony alpha nex-7
Mark_McD
Senior Member
Canon EF 14mm 2.8, 50mm 1.2, 135mm 2 tested:
http://www.lensrentals.com/blog/2013/01/metabones-magic
http://www.lensrentals.com/blog/2013/01/metabones-magic
verybiglebowski
Senior Member
Natural light fall off (caused by lighting on the subject) is visible in the lower part of the image. But on the top of the image, intensity of incident light is highest and with the original firmware of the NEX 7, vignetting is much less pronounced.
So, you might say, that there is overall color layer applied, and the difference in intensity is caused by another vignetting layer, (that change luminosity value in RGB), but to my eye the hue of this green color is rather the same, and it should be affected too, if that is the case.(If applied in the RGB color space)
Nevertheless, it doesn't really matter if it is uniformly applied or graduated, the effect is horrible anyway.
--
...RC's one for SB is perhaps a best example how it should be done and concluded:
"I think it was pretty obvious that I came armed for battle, ready to slam this product as some marketing overhype. I was
It does increase astigmatism a bit, although I doubt this will cause anyone problems unless someone is trying to shoot landscape photography with it. It also seems to create some highlight blooming at very wide apertures. Again, nothing that can’t be worked around and probably not something that will be noticeable with anything but the widest aperture lenses.
It is going to take a while and a lot of people experimenting before we find out what combinations of lenses and cameras are awesome with it, which are fairly good, and which fairly bad. They won’t all be the same. But I suspect most of them are going to be pretty good. And this is going to be a very useful tool.
Most of the little foibles I’ve seen (including the part about adapter tilt) really only apply to photographers trying to tweek every drop of resolution out of their high-resolution sensor. Video, even 5k video, is more forgiving of a slightly weak corner or a bit of astigmatism" .
jpr2
This is pretty interesting stuff. Really exciting for people with decent EF libraries.
Lets hope metabones can push this out for the other mounts too, its pretty impressive. Wonder if they can fit the adapter in a contax G mount? Might be a bit thin unfortunately.
Lets hope metabones can push this out for the other mounts too, its pretty impressive. Wonder if they can fit the adapter in a contax G mount? Might be a bit thin unfortunately.
Someone said it could increase IQ, or equal to.
I also doubt that because from what I've always thought, adding anything to the optical path of a lens that has already been formulated for top IQ already, will degrade the image. I mean even the longer lenses with the Canon's, even the drop in filter has been formulated into the optical path.
Canon, Nikon, etc, can't even make a 1.4x TC that doesn't degrade the image. So I would have to see resolution charts to be convinced of it.
With tele lenses having a vignetting problem, then to me obviously it does degrade the image. Its just a matter of by how much and what focal lengths and designs.
All the best and yep, I can imagine the res charts showing it does degrade for sure.
Danny.
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Erik Magnuson
Guest
If by IQ, you mean resolution in lp/mm, then it can. Here is how: assume a lens can project 50 line pairs on a millimeter of sensor. However, if you "compress" that 50 line pairs so it's projected on only 0.71mm of sensor, then you now have 70 line pairs per millimeter. Even if there is some small optical loss, you still gain resolution (expressed in lp/mm on the image plane).
Even here there is a catch: when talking about lines per inch resolved on the same size print, you have to magnify the smaller image area more and it evens back out.
Teleconverters do the opposite: that 50 lp/mm is magnified to now cover 1.4mm so you have only 36lp/mm. Of course lens resolution is not binary in this way, but you should get the general idea.
Obviously this is a physical device subject to imperfections. It's also a generic design for a variety of lenses and not precisely matched to each lens. In general, it should work very well in the center -- where most optics have similar characteristics -- and less well in the corners.
Excellent read and I'll pour a coffee and go back for more thanks
What can I say, I'm stunned and by the looks its a bit of a shock
Theory is one thing, but to put it into practise is another ball game altogether. Impressive !!All the best and excellent read, on my way back there now thanks. I'm wrong again, LOL.
Danny.
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Thanks Eric and I've learnt a lot from this entire post. Would never have believed it, but there you go
The dead opposite of what I've always thought, but I'm getting the idea for sure. I can see where the corners can suffer and that makes sense.
All the best Eric and a good link at the bottom here from lensrentals.
Danny.
nzmacro wrote:
Excellent read and I'll pour a coffee and go back for more thanks
What can I say, I'm stunned and by the looks its a bit of a shock
All the best and excellent read, on my way back there now thanks. I'm wrong again, LOL.
Danny.
verybiglebowski
Senior Member
Just the hypotheses ... What if the lens in the SB adapter will be mounted in the helicoid mechanism? Would it be possible that way to perform "micro adjustment", for each one of mounted lenses? Something like Fresnel lens torch.
Of course, that will cause the different projection circle resulting in a slightly different FL, but with the ability to improve corner performance if necessary...
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Erik Magnuson
Guest
I don't think that element to element distance is the critical factor - it seems matching the curvature and corrections of the converter to the properties of the light exiting the base lens is the important part. The physical size available for the mount and the converter play a role but I don't think that a simply physical adjustment would help much.
...not exactly end-user operable, as users would need to know pretty well what/how to do it, but still quire close:
"The Speed Booster (SB) reduces the lens-to-image plane distance by 4-6mm depending on the version (NEX or micro 4/3). So the nominal distance between the SB flanges is that much less than a plain adapter. Because there is always a small focal length variation when you build optics we designed the optical cell so that it could be screwed in and out while checking for infinity focus with a collimator. This pretty much solves the tolerance issue". (Brian Caldwell)
jpr2
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Erik Magnuson
Guest
I think the key phrase here is "for infinity focus". For some lenses it might be possible to tweak corners at the expense of the center using this adjustment - only testing will tell.
anyone who ever tweaked adapters which not quite allowed infinity focus will confirm, that distances less than infinity are not a problem usually - most often than not III-party adapters, to mount legacy glass, turn out slightly too thick, and need to be either replaced or carefully shaved. With SB situation seems to be different, as the adjustable optical element introduces an additional degree of freedom = although how much needs yet to be seen
jpr2
captura
Forum Pro
I noted the more preferable results in the LensRentals tests, coming from the Canon compared to the NEX:
"Notice the upper left corner is worse and the upper right better, and that the right side of the image resolves better than the left. The lens, which behaved very nicely on a Canon camera, is tilted when shot on this particular NEX-7 with this particular adapter. So, of course, we went and got another adapter. It tilted the other way. And we were out of time. From experience I can say the center resolution number is going to be accurate, the actual weighted average should be a few points higher and the worst corner about 275 or so rather than 210 (275 is the resolution on the less affected corner)."
"Notice the upper left corner is worse and the upper right better, and that the right side of the image resolves better than the left. The lens, which behaved very nicely on a Canon camera, is tilted when shot on this particular NEX-7 with this particular adapter. So, of course, we went and got another adapter. It tilted the other way. And we were out of time. From experience I can say the center resolution number is going to be accurate, the actual weighted average should be a few points higher and the worst corner about 275 or so rather than 210 (275 is the resolution on the less affected corner)."
...but it makes a lot of sense to think about it !!
The problem is most troublesome for near neutral (gray or whitish) surfaces. However, and this puzzles me, what happens seems to contradict theoretical descriptions - because it should be more pronounced as objects become lighter or more saturated, and the range of possible metamers descreases. And yet what I observe is just the opposite = color casts (both magenta[ish] & cyan[ish]) get stronger with falling light levels on evenly lit surfaces
!!jpr2
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