measuring a wide angle?

[The111 0]

I made a post awhile ago that I was curious how far I could get my 0.3x Diamond wide angle lens zoomed in. A few people chimed in and said it was probably around 0.45x.

I also, through reading around a lot, found out that the wide angle "specs" given for a lens are often not standardized, for example one brand's "0.6" may be actually wider than another brand's "0.5".

So, my curiosity got the best of me and I decided to see if I could crudely measure my lens. I set up a grid on the wall with units of measurement and first looked at it without any lens on the camera, zoomed all the way out. Then I zoomed my camera in to the max, and confirmed that the units were 10 times bigger on the screen (my camera has 10x optical zoom). So that makes sense.

Next I zoomed out again, and then put the lens on. By examining the grid I made, I calculated that the "0.3x" Diamond lens is actually about 0.48x. I'm not complaining, if anything I'm actually glad it's only that wide (assuming my experiment is not faulty) since after buying it I wished I had not gone all the way to 0.3. However, could there be something wrong with my experiment?

Would this lens produce a different picture on different cameras? I have an HC90.

Next, I zoomed in as far as I could with the lens on... to the "pre-blurry point" as we described in the earlier thread. Then I did my calculations again and got close to 0.7x!

So if I'm not doing something horribly wrong, it seems my lens, which I guessed ahead of time had a 0.3-0.45 range, actually has a 0.48-0.7 range!

Any comments? Anybody else ever done anything like this?

www.WingsuitPhotos.com

[Vectracide 0]

All I know is that lens manufacturers are not all alike. I have had 2 differnet .45 lenses. The first one I had was VERY wide. More than my .3. Lost of barrel distortion as well, which was a cool effect. I sold it with my camera and got another new one. I bought the Kenko Titanium .45. What an absolute total piece of shit. I would venture to say that its a .7. I have pics of my master bedroom with the old and the new lens, standing from the same spot in the doorway. There is several, as in 5-6 feet more coverage on both sides with the old lens. Same camera too (PC120). I contacted Kenko, and was basically told to go pound sand.

I am happy with my Diamond .3 I would like to get the .2 sometime soon. But I will more than likely purchase them from Way Cool Industries, as their prices are cheaper and the lens is made from the exact Lat and Long on this earth. Different anodizing and labeling, same exact glass.

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Controlled and Deliberate.....

[Miami 0]

Yep...I had similer questions when I found my .3 and .42 to be exactly the same as far as field of view. Here is that post...it kinda frustrating isn't it?

Miami

[cj1150gs 0]

Hi,

Without searching I dare to say that the multiplying factor stated on conversion lenses is to be applied to the focal lenght of the main lens and not to the linear dimensions you get to see through the lens.

There's some added confusion because conv. lenses are mostly used on video cameras, and these state their zoom range in X times.

Your camcorder zoom is equivalent to, say, a 32-500 mm zoom lens (35 mm film equivalent), so, a conversion lens of 0.5 would make it behave like a 16-250 mm zoom, but the relation between field of view and focal lenght is not linear, AFAIK.

Add to that the usual manufacturers bullshit and no one knows for sure if this conversion lens is widder than the other. I remember founding a link on the internet some years ago where a skydiver compared some conv. lenses and the widdest was a 0.6 Sony (I believe he was comparing with at least a 0.45 from some other brand.

Of course we could all measure our gear in some simple and standardized way, say, this camera, zoomed to widdest sees X linear wide dimension at a Y distance, and with an XPTO brand conversion lens, that linear dimension increased to Z.

Better yet, we can scavange the internet and find someone who already did this

Carlos Martins
Portugal www.cj.smugmug.com

[DSE 3]

FWIW, I'm in the process of rating several lenses for width, resolution, etc. A couple manufacturers have not responded to emails asking for test products, so will be missing a few, as I'm not interested in buying all the various lenses out there. I've already got what I need for my own use.
Anyway, using standard EIA charts and DSCLabs charts, coupled with measuring software.