Tuesday, May 29, 2018

Sigma 30mm f/1.4 Nikon mount APS-C lens on full frame camera--Sony A7


Quite cheaper way to get the f/1.4 lens.

In Korea, secondhand Sigma 30mm f/1.4 EX DC HSM lens was not expensive--about $106 to $130 US dollars, especially Nikon mount. And others like Canon, Alpha mount were more--but not so much.
And secondhand Sigma 30mm f/1.4 for Sony E mount costs around $280.

Other cheap way to get the 1.4 lens is old lens like Takumar 50mm f1.4 or Nikon/Canon 50mm f1.4 which is slightly cheaper than Sigma.
But when put this lens on APS-C camera, it became 75mm lens. Because of crop factor.


According to the Sigma 30mm f/1.4 EX DC HSM lens - Wikipedia web page, on APS-C sensor cameras, its filed of view equivalent to a 46mm lens. Or slightly more for other camera like Canon, older Sigma bodies.


Sigma 30mm f/1.4 EX DC HSM for Nikon mount lens on Sony A7 camera


It can use more than 46mm lens on full frame camera.

When I try to use Sigma 30mm lens on Sony A7, I felt that I can use slightly more than 46mm.
For example, if I shot for portrait or close up(or macro), out of centre area--or out of focus area, don't need sharp--clear image. I mean most of time, that area was blur area. So this case, I can use more than 46mm.




Technical notes:

These photos were all taken with handheld and I used Nikon G lens to Sony E mount(Nex) adapter so I have no idea about aperture number for the photo.

When I do post-processing the raw image file, I prefer to use Rawtherapee-open source software.
But when I am taking photos with not Sony e mount lens--especially old legacy lens, Sony A7 choose very wrong white balance value.
So this time, I choose to use Sony Imaging Edge software for better white balance value--I don't think it can make better but it probably better than Sony A7 camera's.


Imaging Edge value setting:
 - Brightness: +0.33 ev (1 stop)
 - White balance: Preset to 'Auto'
 - Creative style: Landscape or Standard
 - Jpg compression level: 2 (total 4 level and one level lower than high quality setting)

like this:
screenshot of Imaging Edge - value setting


I didn't do any other editing, especially sharpening the image.  So you can see how Sigma 30mm f1.4 Nikon mount lens performs on Sony A7 camera.


Sony A7 - APS-C Size Capture setting in menu

Sony A7 can automatically crop when the APS-C lens was used. Which can set (on, off or Auto) the APS-C size capture in Sony A7's menu.


So first photo was full frame capture.
And second photo was turn on the APS-C size capture.

full frame image

APS-C Size Capture - On image


You can manually crop the image like this:
screenshot of Faststone Image Viewer's crop board.

Sony A7 can capture 6000 x 4000 = 24MP(MegaPixel).
APS-C size capture - On can capture 3936 x 2624 = 10.33MP
crop the image manually like above - 4401 x 2934 = 12.91MP

But when I crop the image manually, image's edge side won't be very good. Because lens wasn't design for those areas.

crop the image manually from full frame.


Other example:
full frame image

APS-C Size Capture - On image


full frame image
APS-C Size Capture - On image


This photo's out of centre and out of focus area are blur so it can crop the image more than previous image--like this:
4893 x 3262 = 15.96MP - bigger than previous one--3936 x 2624 = 10.33MP.
screenshot of Faststone Image Viewer's crop board.

crop the image manually from full frame.


If I'd like to make more bigger size, I can do like this:
screenshot of Rawtherapee's crop image

5357 x 3356 = 17.98MP.
crop the image manually from full frame.

Corners and edges are very dark and not so great. But I think it was quite usable.


So having a APS-C lens on full frame camera wasn't bad idea, I think.

This lens wasn't design for the full frame so you shouldn't expect better result on corner area though.



Another sample photo from my flickr account:
City roses. (Sigma 30mm f/1.4 APS-C lens on full frame camera)


P.S. If you'd like to read in Korean, you can read it from here--this is my Korean blog.

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