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Zoom range on CP 995 is smaller than advertised
- Thread starter MC52021
- Start date
Bryan Biggers
Veteran Member
It was the same way on the CP950 and CP990. On this page...
http://webpages.charter.net/bbiggers/DCExperiments/html/990_usage_tips.html
you will find the explanation for the CP990.
"This is a very unusual 990 tidbit, and I'm not sure where to put it, so I'm putting it here on the tips page.
If you are shooting normally, and you zoom out to wide angle, the camera will take shots at 8.2mm focal length. If you set the fisheye1 lens, the camera will zoom out to 7.7mm! The 7.7mm setting is only available with the fisheye1 setting, and the focus is fixed at infinity, so this can't be used for everything. It is slightly wider angle than the normal wide angle setting. This may be why the lens can be advertised as a 3X zoom when it is not quite 3X over the normal range. I have no idea why this is done... does it vignette slightly at that setting, and this would not be noticed with the fisheye lens on? I don't notice any vignetting on my camera. Maybe the focus mechanism can't focus over the whole range at that setting so that only infinity focus is available, so that might be why it isn't normally available? I have no idea. It is slightly wider though, and could be useful.
Note that Danny Lauring reports that this does not work on the 950.
"
Apparently they are counting the little extra wide angle that you can get in the fisheye position (and I think that the 995 is the same as the 990) in computing the "X" of the zoom lens. The 950 however did not have a good excuse, and was always about 2.8X zoom instead of 3X.
Bryan
G
gene
Guest
Thanx Bryan. Too bad I didn't know that Saturday when I was 205 feet in the air :-( Will make a note of it for next time though. Thank you again.
Gene.
Gene.
Peter iNova56624
Leading Member
Try it this way. I did. Shoot a yardstick (3 feet) at wide angle from the distance at which the yardstick exactly fills the monitor side to side. Pretty easy to set up.
Now zoom to full tele. How much yardstick is in the shot?
When you do this with a 990 using the F1 setting for wide, the lens actually shows a bit GREATER than 3:1 zoom.
That number you see in the Exif data is machine info, too. Not a metric test of the actual performance of your lens. And each lens varies slightly.
The mm numbers are one test of zoom range. The actual width of a subject is another. Shoot a picture of anything at both extremes and see what number you need to put into Photoshop to blow the tele image down to fit inside the wide shot. The reciprocal is the zoom range.
Done this way with a 990, a tele image shrunk to 35% of original size just about exactly fits on top of the wide shot. That implies 2.85:1 zoom. Or another way of looking at it is that a perfect 3:1 zoom would use 33.333% as the reduction factor. And my tele image is a whopping 1.67% too big, causing me to have to shrink it less. How dare they short change me 1.67%!! I'll sue!
The 995 shows a real-world 3.85:1 zoom as measured with the yardstick method. But to fit the tele image on top of the wide shot, the reduction was 26.08% instead of a "perfect" 25% for a "true" 4:1 zoom. So at the extreme, that's what this is all about. A measley 1.08% or 1.6% (990) difference in magnification at the tele end of the longest zoom position. Where's the beef?
Incidentally, my 995 does NOT go that extra slight bit wider in F1 position. Does anybody's? It cuts off my fisheye circle at the top. Geez.
-iNova
I agree that the difference in maginification is really small but if you look at the ratio of 3.8 to 4 you will get that the zoom range is about 95% of advertised. That's a 5% difference. Just another way to look at the numbers 
Peter iNova56624
Leading Member
Right. And remember: Numbers NEVER lie, exaggerate or confuse. Well, at least 92.7554% of the time...I agree that the difference in maginification is really small but
if you look at the ratio of 3.8 to 4 you will get that the zoom
range is about 95% of advertised. That's a 5% difference. Just
another way to look at the numbers
When you blow up 26.08 (the enlargement ratio between tele and wide) x 3.83425 you get 100. Making that tele a lousy 1.08% off perfect 4:1. Another way to look at the numbers.
-iNova
Yes, numbers don't lie or exaggerate. People do (marketing department people do it more often than others - just my observation)
Sometimes even a 0.5% could be important, although definitely not in this case.
Sometimes even a 0.5% could be important, although definitely not in this case.
Right. And remember: Numbers NEVER lie, exaggerate or confuse.I agree that the difference in maginification is really small but
if you look at the ratio of 3.8 to 4 you will get that the zoom
range is about 95% of advertised. That's a 5% difference. Just
another way to look at the numbers
Well, at least 92.7554% of the time...
When you blow up 26.08 (the enlargement ratio between tele and
wide) x 3.83425 you get 100. Making that tele a lousy 1.08% off
perfect 4:1. Another way to look at the numbers.
-iNova
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