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02-24-2009, 07:46 AM   #16
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Well it's all about marketing because a super zoom that can cover such a wide focal range is very appealing to many. A lot of people fall prey to the claims made in marketing literature and make buying decisions based on specs and not actual tests.

Just recently I spent a long time convincing a Canon user this very issue, in his case his IF macro lens actually altered the focal length at maximum magnification.

02-24-2009, 07:52 AM   #17
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it's really a shame that.......

specifications, and testing do not require posting the true focal length as a function fo focusing distance.

I remember a time when camera magazines for example tested and reported the true focal length , and the true apature of the lens the manufacturer's gave them for testing.

I guess that time has passed.
02-24-2009, 12:03 PM   #18
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QuoteOriginally posted by Alfisti Quote
All the more reason why those muppets saying the 18-250 covers the 55-300 aree just plain wrong. It barely covers the 50-200.
The muppets said that? Which one? Is it the one in the purple hat? He looks like a Pentax shooter:

02-24-2009, 04:08 PM   #19
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QuoteOriginally posted by Alfisti Quote
All the more reason why those muppets saying the 18-250 covers the 55-300 aree just plain wrong. It barely covers the 50-200.
To be fair though, it does begin do work that way once you're a decent distance from the subject. I do agree with you that people who think that an 18-250mm lens is not highly likely to have more design compromises than a 50-200, or probably even 55-300 are being extremely naively optimistic.

QuoteOriginally posted by PentaxPoke Quote
The muppets said that? Which one? Is it the one in the purple hat? He looks like a Pentax shooter:
It's british / aussie / kiwi (maybe canadian too?) slang for an inept or clueless person.

02-24-2009, 04:14 PM   #20
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QuoteOriginally posted by Lowell Goudge Quote
specifications, and testing do not require posting the true focal length as a function fo focusing distance.

I remember a time when camera magazines for example tested and reported the true focal length , and the true apature of the lens the manufacturer's gave them for testing.

I guess that time has passed.
I remember reading reviews in Popular Photography when the IF superzooms first came out and this was discussed, but it was buried in the reviews. I'd also read letters where user's complained of this shortening of focal lengths and the mags gave an honest answer. Granted, they did not make a big deal of it though, not wanting to bite the hand that feeds them......
02-24-2009, 06:22 PM   #21
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QuoteOriginally posted by frank Quote
James is right on this one. If you shoot something far away, like a building several hundred meters away, then you compare both, you'll see the 'actual' focal length of this 18250 lens :0 When you focus at close target, the focal length becomes shorter.
If this was the case, wouldn't the size of the object appear to change as you focus from near to infiinity? It seems that this would be a very noticeable effect.
I don't own a 18-250, so I don't know how it operates. I do have a Sigma 100-300 which is internal focus, now I'm going to have to find out if it has this bizarre behavior.

Tom
02-24-2009, 06:41 PM   #22
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QuoteOriginally posted by pentaxman Quote
If this was the case, wouldn't the size of the object appear to change as you focus from near to infiinity? It seems that this would be a very noticeable effect.
I don't own a 18-250, so I don't know how it operates. I do have a Sigma 100-300 which is internal focus, now I'm going to have to find out if it has this bizarre behavior.

Tom
Yes, the object size would change in the viewfinder (and on the final photos) during focus This isn't very obvious for a lens like 100-300 even it's an IF lens. But it's quite obvious for a lens like 18-250 or 18-200.
02-24-2009, 06:43 PM   #23
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QuoteOriginally posted by cpopham Quote

It's british / aussie / kiwi (maybe canadian too?) slang for an inept or clueless person.
"muppet" to an American has an entirely different meaning.

02-24-2009, 07:11 PM   #24
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QuoteOriginally posted by PentaxPoke Quote
"muppet" to an American has an entirely different meaning.
Oh they exported the TV show around the world. I believe it's even a slang use of the name of the show. It's just that it's also used as a mild insult in some english speaking countries - which might make the original comment make more sense.
02-24-2009, 08:59 PM   #25
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QuoteOriginally posted by frank Quote
Yes, the object size would change in the viewfinder (and on the final photos) during focus This isn't very obvious for a lens like 100-300 even it's an IF lens. But it's quite obvious for a lens like 18-250 or 18-200.
You're right - the image size does noticeably change when I am focusing my 100-300 Sigma zoom. I also tried my DA* 50-135 and it changes size also (internal focus) I never noticed this before.


I tried my DA* 300mm and it does not have any apparent change in focal length even though it is internal focus.
02-24-2009, 09:04 PM   #26
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Fozzy Bear is always shooting his mouth off, I bet it was him.
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