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Old 03-01-2009, 11:15 AM
John Weaver
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f2.8 lens does it get you that much more?

Hi all
70-200mm canon f4 or f2.8.
Drooling over Dugnsuz pics (yes i am a Dugnsuz wantabe)I just can't get over wide field.
My question what would be the difference?
Less noise because less exposure time?
Better light grasp?
Clarity?
Twice the price!http://www.iceinspace.com.au/forum/....s/sad_eyes.gif
I just want to future proof my self as the budget won't allow in my case stuff ups
regards John
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  #2  
Old 03-01-2009, 11:37 AM
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rogerco (Roger)
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I assume you are talking in terms of astronomy wide field photography. I don't have a lot of experience in astronomy terms but in general photography I can offer an opinion.

If you are questioning the expenditure and the 2.8 is twice the f4 then get the f4. The difference is not quite half the light. In dim light normal photography the 2.8 would make critical focusing easier but not much and nothing in terms of astronomical focusing. I doubt it makes much difference in terms of astronomical exposures.

Not sure what the lens is made of, but weight might be an issue depending on your mount, then again the money saved may allow you to get a better mount that might add more to your astrophotography than a 2.8 would.

Roger
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Old 03-01-2009, 12:06 PM
Ian Robinson
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http://www.canon.com.au/products/cam...usm_specs.aspx

Filter Diameter:
67mm

Horizontal Angle of View:
29 - 10

Weight:
760g

http://www.canon.com.au/products/cam...usm_specs.aspx
Filter Size:
77mm

Weight:
1570g

Angle of View:
34 degrees to 12 degrees


Extra 10mm aperture (not much but enough to help get that little bit deeper for the same exposure).
Extra stop means if you had the same size objective (front) lens you need 1/2 the exposure to record fuzzy or diffuse stuff like comets, galaxies, nebulae with the f2.8 cf f4 lens for a given ISO setting.

If you are worried about an additional 810g then your mount is way too small anyway, so go for the f4 and use the $ saved to upgrade to go towards a more capable GEM.

In non-astro photography , I think the extra stop is certainly worth having , so is the IS , means you can shoot in lower light without needing to resort to using a flash (esp handy if you are interested in sports, dance, and photography of wild life and scenary when on holidays), and it also means you can get away without a tripod for longer exposures (is like an extra 3 or 4 stops it is said).

Some think the IS results in less crisp images , I've not seen anything published that indicates this for astroimaging , where the IS option would be disabled anyway.

I plan on getting an EF 70-200mm f2.8 L IS USM + a 2x TII EF Teleconvertor when the exchange rate is more acceptable.

Last edited by Ian Robinson; 03-01-2009 at 12:37 PM.
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Old 03-01-2009, 12:35 PM
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AlexN
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Firstly, is it going to be for astronomy only? or will it be used for other photography as well? If astro only, the 200 F/2.8 prime is probably where you want to be looking... If it will be a multi-purpose lens, then the 70-200 2.8 is a great lens indeed.. as is the F/4

Having 2.8 will not have less noise due to less exposure time, More exposure time raises the signal to noise ratio, hence, more exposure time = less noise.. Clarity? Well.. the 4 different 70-200L lenses are of all very clear, however, the F/4L IS is know to be the sharpest. followed by the F/2.8L IS, then the F/4L, then the F/2.8L. These differences in sharpness will go unnoticed to most people, however in side by side tests, you can usually tell the differences.

Also, the 200 F/2.8L prime lens is sharper than them all again, at the cost of loss of some versatility, but if the lens is for astro work only, you'd be hard pressed to find better in this price range... Whats more, if you were to buy the 200 F/2.8L prime instead of the 70-200 F/2.8L, you'd have enough spare change to buy the 85mm F/1.8 which would give you extremely sharp images and give you some versatility....

I've owned the 70-200 F/4L (non IS) and the still have the 70-200 F/2.8L IS, More often than not, I use the 200 F/2.8 prime...
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Old 03-01-2009, 01:07 PM
John Weaver
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Yes I was referring to astronomy wide field photography and I am now leaning toward canon prime lenses 50mm and 85 mm f1.8 I have heard
great reports about the 200 f2.8 lens.
Thanks for your thoughts
john
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Old 03-01-2009, 01:37 PM
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You're welcome John... For the price for the 70-200 F/2.8L IS you could have the 200 F/2.8L, 50 F/1.4 and 85 F/1.8
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Old 05-01-2009, 04:53 PM
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dugnsuz (Doug)
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Quote:
Originally Posted by John Weaver View Post
Hi all
70-200mm canon f4 or f2.8.
Drooling over Dugnsuz pics (yes i am a Dugnsuz wantabe)I just can't get over wide field.
My question what would be the difference?
Less noise because less exposure time?
Better light grasp?
Clarity?
Twice the price!http://www.iceinspace.com.au/forum/....s/sad_eyes.gif
I just want to future proof my self as the budget won't allow in my case stuff ups
regards John
Hi John - thanks for the endorsement, that's a first!!

I bought the f4 purely on "bang for buck"...so many glowing reviews swayed my decision too - and, the f2.8 was/is out of my budget. The lens is used 90% of the time for astro work so IS wasn't needed either.
I would imagine even with the f2.8 you may want to stop it down to sharpen up the stars anyway - could be wrong as I say...imagining!!!
As stated the lens on the 2.8 is 10mm bigger than the f4 - bigger light grasp , less exposure time. But, needs a more costly filter if you go down that route.
I'm very pleased with the lens and extender too and I 've found that I have reached a happy place with my setup where I'm not consumed in drooling/stressing over the next purchase ( I assume this is a temporary state of astro-enlightenment and probably won't last the week!!!!).
f2.8 or 4 - don't think you'll go wrong with either.

Bottom line - if I was in the market for a lens and had the cash I would go for the 2.8, but because of the results I've had with the f4 I won't be saving up for one - the retrospectroscope has saved me some money at last!
All the best
Doug
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