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What about a wide conversion lens?
#1
I have no experience with it. Attaching a wide conversion lens to a specified normal lens can make the lens wider. I want to know the effect on IQ: sharpness, distortion, vignetting, flare, focussing, etc. I also want to know if the wide conversion lens changes the aperture of the lens. Does any body have experince with a wide conversion lens?



A specific example that draws my attension is the new pana DMW-GWC1. According to the descrption, it can be attached to a pana 14mm f2.5 to make it an 11mm lens (not mentioning the aperture). If the IQ is not reduced much, then it sounds a good deal to have a detached 14/2.5 (low price) + a DMW-GWC1. Then you will get two (U)WA lenses: an equiv. 28mm/f5 + an equiv. 22mm/f5(?). What do you think?



Thanks,

Frank
#2
I just read from the panasonic site that "All Panasonic conversion lenses are front conversion type lenses, so the camera's F-stop is unchanged". (See http://panasonic.jp/support/global/cs/ds...how23.html)
#3
Don´t know how the 14/2.5 lens is with this specific wa-converter, but in general you lose a lot in image quality. Most wa-converters are cheap, and you get what you pay for. Wa-converters are mainly used for film.



Göran
#4
[quote name='goran h' timestamp='1340108478' post='18971']

Don´t know how the 14/2.5 lens is with this specific wa-converter, but in general you lose a lot in image quality. Most wa-converters are cheap, and you get what you pay for. Wa-converters are mainly used for film.



Göran

[/quote]



The Sony NEX WA converter was tested here along with the E16mm lens. The results seemed pretty good, all things considered, in that it didn't significantly degrade the IQ. The biggest issues for me would be that the WA converter adds complex distortion and I don't think the EXIF data would reflect the converted field of view. But for ~$130 it's not a huge risk combined with the 14mm lens.
#5
Actually wide angle converter can make a lens "faster". An example of this is the Olympus 35-100mm f2. This lens is essentially a 70-200mm f4 lens with a 0.5x wide angle converter in front.



Wide angle converters usually also do not make a lens lose a lot of resolution either. Unlike tele converters they do not "crop" the original glass. If the wide angle converter has good optics, results generally are quite good.
#6
I bought the Lumix DMW-GWC1 converter a month ago off eBay from Tokyo for $180 USD and mounted it on my Lumix 14mm f/2.5, attached to a Lumix GF2 body (M4/3)



After several pictures and careful pixel peeping comparison with/without the converter, I'm very impressed.

There's no significant loss of resolution except slightly in the extreme corners.



Barrel distorsion is higher but to me it seems just normal for a 22mm equivalent.



There's no loss of luminosity detected from the metering system.



I would recommend it to anyone on a budget looking for a quality fast wide angle.

It is wider than the Olympus 12mm f/2, reasonably sharp and cost a quarter of the price.



But I'd be curious to see if my observations stand after a PZ analysis.
#7
Thank you all for your kind responses. It seems the WA converter is pretty good. I also find some sample images at dpreview (but not 100% size), they look remarkably good: http://forums.dpreview.com/forums/readfl...322&page=1



From the information that I gathered, a WA converter does not change FL, does not change aperture, so it also does not change the DoF at the same focus distance.



I think the DMW-GWC1 will be tested by PZ when new reviews on the X 14-42 and/or the 14/2.5 are published.
#8
[quote name='dave9t5' timestamp='1340110123' post='18972']

The Sony NEX WA converter was tested here along with the E16mm lens. The results seemed pretty good, all things considered, in that it didn't significantly degrade the IQ. The biggest issues for me would be that the WA converter adds complex distortion and I don't think the EXIF data would reflect the converted field of view. But for ~$130 it's not a huge risk combined with the 14mm lens.

[/quote]



Yes, I have read the review. It appears that the WA converter does not affect the MTF values at all.
#9
[quote name='Frank' timestamp='1340159622' post='18976']

Thank you all for your kind responses. It seems the WA converter is pretty good. I also find some sample images at dpreview (but not 100% size), they look remarkably good: [url="http://forums.dpreview.com/forums/readflat.asp?forum=1041&thread=41477322&page=1"]http://forums.dprevi...41477322&page=1[/url]



From the information that I gathered, a WA converter does not change FL, does not change aperture, [color="#0000ff"]so it also does not change the DoF at the same focus distance[/color].



I think the DMW-GWC1 will be tested by PZ when new reviews on the X 14-42 and/or the 14/2.5 are published.

[/quote]

You're wrong there. It does change DoF, by the same factor that it actually dminishes the FL.It also changes the resulting FL. The only reason it doesn't change the aperture is because it uses the diaphragm and aperture placement of the original imaging lens.



Essentially, this works a bit like a static zoom lens, if you like. A zoom lens has an imaging group or groups of lenses, a group or groups of lenses which essentially determine the angle of view, and a group or groups of lenses which image the object onto the sensor. Essentially, a WA (or tele) converter which is front mounted is a new imaging plus static set of lens groups, where the lens this is fixed to behaves like the lens imaging the object as seen through the converter on the sensor.



This means that the imaging part of the convertor needs to deliver a (virtual) image large enough that it will not vignet when imaged by the lens it is attached to.



As to how well it works: it will never work as well as a decent prime lens of the resulting FL, not even with a specific, dediated attachment, for the simple reason that it is an afterthought and therefore not an optimal solution for a specific FL.



Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....
#10
Thank you, Wim. I understand it better now.



Best regards,

Frank





[quote name='wim' timestamp='1340220835' post='18994']

You're wrong there. It does change DoF, by the same factor that it actually dminishes the FL.It also changes the resulting FL. The only reason it doesn't change the aperture is because it uses the diaphragm and aperture placement of the original imaging lens.



Essentially, this works a bit like a static zoom lens, if you like. A zoom lens has an imaging group or groups of lenses, a group or groups of lenses which essentially determine the angle of view, and a group or groups of lenses which image the object onto the sensor. Essentially, a WA (or tele) converter which is front mounted is a new imaging plus static set of lens groups, where the lens this is fixed to behaves like the lens imaging the object as seen through the converter on the sensor.



This means that the imaging part of the convertor needs to deliver a (virtual) image large enough that it will not vignet when imaged by the lens it is attached to.



As to how well it works: it will never work as well as a decent prime lens of the resulting FL, not even with a specific, dediated attachment, for the simple reason that it is an afterthought and therefore not an optimal solution for a specific FL.



Kind regards, Wim

[/quote]
  


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