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08-26-2009, 03:05 AM   #16
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Thanks Ben

I knew you would come through. My learning curve continues. You are my go to guy on technical issues surrounding lenses and such. You even taught me a new word - "variator". So, long story short - a good 300mm will stiil outperform a good zoom at the same focal length. Right?

Tom G

08-26-2009, 05:16 AM   #17
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QuoteOriginally posted by 8540tomg Quote
So, long story short - a good 300mm will stiil outperform a good zoom at the same focal length. Right?

Tom G
A good prime will outperm almost any zoom. To top the Sigma 100-300/4 it takes a very good prime lens indeed, whereas that particular zoom will demolish any mediocre prime lens. The DA 300/4 may for instance outperfom the 100-300/4 slightly. But you will only see that in pixel-level comparisson of images taken under optimum conditions (tripod, good light etc.) But the DA 300 will significantly (for me, that is visibly) outperfom all these 70-300 or even worse 28-300 zooms.

Ben
08-26-2009, 08:04 AM   #18
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You just made me glad I never got the 18-250.

Instead I went for the 50-135... I can see now based on your discussion that the limited focal range on this lens may also mean better quality.
08-26-2009, 08:11 AM   #19
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QuoteOriginally posted by esman7 Quote
You just made me glad I never got the 18-250.

Instead I went for the 50-135... I can see now based on your discussion that the limited focal range on this lens may also mean better quality.
You summed it up nicely: a limited zoom range is a good way to secure top-performance (not all manufactureres succeed to do so, though). The 50-135 seems to be as good as it gets.

Ben

08-26-2009, 08:44 AM   #20
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Would you say it's safe to look at it as the range divided by the shortest focal length? The lower the ratio the better?

i.e.

18 - 250 = (250-18)/18 = 12.8

70 - 300 = (300-70)/70 = 3.3

50 - 135 = (135-50)/50 = 1.7

12 - 24 = (24 - 12)/12 = 1

Obviously, glass quality and f number means a lot... but just to illustrate.
08-26-2009, 10:50 AM   #21
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Cos they're good at what they do.
08-26-2009, 11:28 AM   #22
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QuoteOriginally posted by esman7 Quote
Would you say it's safe to look at it as the range divided by the shortest focal length? The lower the ratio the better?

i.e.

18 - 250 = (250-18)/18 = 12.8

70 - 300 = (300-70)/70 = 3.3

50 - 135 = (135-50)/50 = 1.7

12 - 24 = (24 - 12)/12 = 1

Obviously, glass quality and f number means a lot... but just to illustrate.
If it works for you, sure, but a "Bigma" (Sigma 50-500mm) would have a value of 9 on this scale, and from what I've seen it's quite a bit better than a Pentax 50-200 (@ 3) in the same zoom range (w/ equiv. f #s). I think some might even argue that the 18-250 trumps the 50-200 in the equiv. range.

There are too many variables - this is why fotozone.de and lenstip.com and other review sites exist. And my DA 10-17 gets a value of 0.7 but the 50-135 is way better!
08-26-2009, 01:35 PM   #23
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QuoteOriginally posted by esman7 Quote
Hi, just wondering why a great number of people are content with lenses such as a 300mm fixed focal length lens. At that range, wouldn't people much rather have somewhat of a range?

I guess if you're trying to shoot really far and you want to be able to crop... that's cool or for macro stuff (is that the main reason)???

Just beware that if it's for some crazy reason, i may have to end up buying one
when you talk about a telephoto vs a telephoto zoom, many times you find you are always at the long end.

think about the issue another way, you have a specific image size on the sensor

image size = subject size x focal length / distance.

now you want to take a photo of a butter fly, 20 meters away, no matter what zoom you will have you will beat maximum, and want even more length,

zooms are useful to a point, but primes are, as some pointed out much lighter per mm of focal length, and if you are always at maximum, you are wasting a lot on capability you don't use.

That is why, for example, I use a teleconverter on my 70-200F2.8. in the case of the 2x TC I am almost always at 400mm, but with the zoom alone I am using both the entire range and 2 F stops of speed advangate. A 70-400 lens would never be F2.8 at 70, and weigh a lot more (like the bigma) it is for me just not interesting to have the range all in 1 lens

08-26-2009, 08:11 PM   #24
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QuoteOriginally posted by panoguy Quote
If it works for you, sure, but a "Bigma" (Sigma 50-500mm) would have a value of 9 on this scale, and from what I've seen it's quite a bit better than a Pentax 50-200 (@ 3) in the same zoom range (w/ equiv. f #s). I think some might even argue that the 18-250 trumps the 50-200 in the equiv. range.

There are too many variables - this is why fotozone.de and lenstip.com and other review sites exist. And my DA 10-17 gets a value of 0.7 but the 50-135 is way better!
My rough formula is price / zoom factor (where zoom factor is max focal length / min length, just as it for P&S cameras - the "X" factor). The bigger the zoom factor, the worse the lens, unless it's enough more expensive to make up for the higher zoom ratio. Still not perfect, but it seems to capture something worthwhile. Probably still underrates the 18-250, though.
08-27-2009, 01:22 AM   #25
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QuoteOriginally posted by panoguy Quote
If it works for you, sure, but a "Bigma" (Sigma 50-500mm) would have a value of 9 on this scale, and from what I've seen it's quite a bit better than a Pentax 50-200 (@ 3) in the same zoom range (w/ equiv. f #s). I think some might even argue that the 18-250 trumps the 50-200 in the equiv. range.

There are too many variables - this is why fotozone.de and lenstip.com and other review sites exist. And my DA 10-17 gets a value of 0.7 but the 50-135 is way better!
The Bigma is one of those exceptions to the rule, that IQ decreases with the zoom factor. But as Marc wrote, the Bigma is way more excensive, than the usual super-zoom and it doesn't start with a wide angle (at 50mm), which makes the design a bit more forgiving. All in all it is a wonderful lens and certainly a very good value in terms of price versus performance.

When discussing the merrits of prime lenses over zooms, we should not completely ignore the versatility factor of a zoom lens. Sometimes this is more important, than the last bit of IQ.

Ben
08-27-2009, 06:23 AM   #26
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QuoteOriginally posted by Ben_Edict Quote
When discussing the merrits of prime lenses over zooms, we should not completely ignore the versatility factor of a zoom lens. Sometimes this is more important, than the last bit of IQ.

Ben
show me anyone who has the bigma in a studio for portraits

Although the lens would certainly generate some interesting looks for the models

the versitility issue is more a marketing ploy than anything else, it can be used in emergencies would be a better approach.
08-27-2009, 08:14 AM   #27
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QuoteOriginally posted by Lowell Goudge Quote
show me anyone who has the bigma in a studio for portraits

Although the <BIGMA> would certainly generate some interesting looks for the models

the versitility issue is more a marketing ploy than anything else, it can be used in emergencies would be a better approach.
"Excuse me while I whip this out" would take on a completely new meaning.
08-27-2009, 08:36 AM   #28
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QuoteOriginally posted by Lowell Goudge Quote
show me anyone who has the bigma in a studio for portraits

Although the lens would certainly generate some interesting looks for the models

the versitility issue is more a marketing ploy than anything else, it can be used in emergencies would be a better approach.
As far as I see, we are discussing super telephoto lenses, not portrait lenses and sure not for studio shoots.

Ben
08-28-2009, 09:01 PM   #29
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Now that the technical stuff is provided, go and rent a da*300mm f4 for a week and try it out. the answer as to why will become evident
08-28-2009, 09:50 PM   #30
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QuoteOriginally posted by esman7 Quote
Would you say it's safe to look at it as the range divided by the shortest focal length? The lower the ratio the better?

i.e.

18 - 250 = (250-18)/18 = 12.8

70 - 300 = (300-70)/70 = 3.3

50 - 135 = (135-50)/50 = 1.7

12 - 24 = (24 - 12)/12 = 1

Obviously, glass quality and f number means a lot... but just to illustrate.
Generally, it's just given as maximum divided by minimum: the DA* 50-135mm is a 2.7x zoom.
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