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Monday, 6 June 2011

Comparison Between My Two Wide-angle Conversion Lens

Here are some tests between the two wide-angle conversion lens I now own: The Fujiyama 0.45x and Vitacom 0.25x conversion lens.

Taken with Fujiyama 0.42x wide-angle conversion lens on Canon 18-55mm kit lens
Taken with Vitacom 0.25x Ultra super wide-angle conversion lens on Canon 18-55mm kit lens 

Taken with Vitacom 0.25x Ultra super wide-angle conversion lens on Tamron 18-270mm zoom lens
These two pictures were taken from the same spot. The images have been resized down to 800x800. First 2 images were taken with the Canon kit lens, the first was Fujiyama 0.42x conversion lens and the second was Vitacom 0.25x conversion lens. 

I would say that the angle has been increased by quite a bit, judging from how much more of the table can be seen from the bottom right hand side in the image. 

The other thing I notice, is how much the image quality of the Vitacom 0.25x deteriorates at the edges of the image. It is apparent even at 800x800 resolution. The same features in the bookshelf on the top left, like a the binded spine of a book and vertical lines are very obviously blurry. 

I wanted to find out if the image quality would be any different on my new Tamron 18-270mm zoom lens, so I took the third image, the Tamron zoom lens with the Vitacom 0.25x conversion lens. Seems like the Tamron gives a softer image overall, but the test is in no way conclusive due the following: The camera was hand-held, not mounted on a tripod, therefore the framing across the 3 pictures are not exactly the same.

This is the initial test, and I'll try and do more tests under different conditions.

The Vitacom does not have a true 180-degree coverage, but I wonder if it is enough for me to use it as an accurate environment map as well as take images for image-based lighting purposes.

Crazy Camera Equipment Splurge!

Giving in to a sudden splurging urge, I went into a camera store at Peninsular Plaza and bought the following:
- an 18mm-270mm Tamron B008E zoom lens (F/3.5-6.3)
- a 0.25x Vitacom Ultra Super Wide-angle auxiliary conversion lens with Macro (52mm in diameter) (cuts light by 1 stop)
- a lens cleaning kit
- a uv filter for 62mm (for the Tamron zoom lens)
- an "i Case" dry box (with attached Hygrometer)

All that cost me $1130. The shop was called Photocam. I was originally going to Cathay Photo to check out prices. But strangely it was closed on Sundays. Across the shop was a small shop but lined with equipment. So I went in.

The story is, I already have a Fujiyama wide-angle conversion lens, which does 0.42x of the original zoom. I got it in Hongkong during my honeymoon. It had a very filmsy rubber cap that came off so easily, I came close to losing it in a few occasions since I had it in April 2011. So the reason I went to the photo shop was to buy me a lens cap for the wide-angle converter. I was also looking out for a zoom lens that's within the range of 18-300mm. 

I believe the people that attended to me was the boss and his wife at the store. Turned out the diameter of my huge lens cap for the Fujiyama wide-angle conversion lens is 72mm. The boss told me my conversion lens was "wrong", not made for my Canon 18-50mm kit lens, because the lens diameter had to be converted to fit the 58mm. (In the end the Vitacom conversion lens also needed a conversion ring too. It was 52mm and my kit lens was 58mm). They gave me a good price for the 18-270mm lens, and gave me a lens cleaning kit, a uv filter, a lens string, and an sd-card storage pouch.

When I was considering whether to buy the Vitacom wide-angle conversion lens, I had the option to buy a lens similar lens that does not show the black areas in the picture. That means I could have a bought a lens giving me a similarly distorted fish-eye image without having to crop the image in post. That would've made better use of the recording areas in the CMOS sensors right? I don't know if I am a fool to have bought the one that distorts my view into a circle. I wanted to see if I could use it for making an environment map.

My new toys on my messy table! Top row from left: Vitacom 0.25x Ultra Super Wide-Angle Auxiliary conversion lens, Tamron 18-270mm zoom lens, and the older Fujiyama 0,42x wide-angle conversion lens (and lots of conversion rings) and lens caps!

The 2 following photos were taken with the Vitacom wide-angle conversion lens. This is using the macro feature. The lens can virtually touch the subject in a macro shot. The only thing that stopped me from doing that was the fact that I would cast my own shadow onto the subjects.



Speaking of the 0.42x and 0.25x wide angle "zoom factor" (how many times zoom). I haven't really figured out what the that means, but as of now, I believe a less-than-one value means it actually increases the field of view, (hence its a wide-angle lens conversion), and a larger-than-one value would mean that the lens decreases the field of view, giving us a zooming-out result. 

Therefore, my 18mm focal length would be converted to (18*0.42)mm, this increases the 18mm field of view to look like a 7.56mm. So now with this new Vitacom Ultra Super Wide-angle conversion lens at 0.25x, it would convert my18mm into a 4.5mm lens! Unfortunately, there is a crop-factor in my Canon 500D sensor (22.5mm x 15mm), as compared to 36mm x 24mm (this is the reference "full frame" film back on 35mm film cameras). The ratio of Canon 500D's image sensor to a 35mm film back would be the 1.6x crop factor. Thus my converted wide-angle focal length of 4.5mm will effectively be increased to be approximately (4.5mm * 1.6 ) = 7.2mm.

For more information on Crop factors (aka Focal length multiplier) and effective focal lengths, here are some links from: TheDigitalPicture.com and Wikipedia.org. Here's another link to Wikipedia on the fisheye lens.