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just got a Sigma 120 - 400 OS HSM, i have a Canon 400D now with this having a cropped sensor this lens becomes 180 - 600 focal length is that correct ?
i also own a Canon 70 - 300 IS HSM lens yet when you compare both lenses there isnt that much more magnification in the sigma, call me thick if you want, but am i missing something
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I think you will find that the difference between a 300mm lens and a 200mm lens is greater than the difference between 300mm and 400mm. Also I think you will find that the 400mm is an approximate value, it may be @ 370mm for example. So no I think you are probably correct. Some lenses also effectively become shorter focal lengths as they focus to a close up object.
Your focal length conversion is correct for the effective focal length, in essence each lens gets multiplied by 1.6, compared to the effective field of view on a full frame camera.
The Canon is equivalent to 110 - 480, either way it's only an increase of 25% at the long end
Quote: just got a Sigma 120 - 400 OS HSM
If you bought it new and have only had it a few days, See if they will swop it for the 150-500mm version.......You'll notice the difference then for sure....!
Isn't this the angle of view measurement that sets the magnification (visable area) depending on subject distance
Sigma 120-400 - Angle of View 20.4 - 6.2 degrees
Canon 70-300 - Angle of View 29° - 6.5 degrees * see PS below as i'm unsure on this figure for comparison.
I must confess, i'd have expected a bigger difference before i looked it up
While i'm there
the sigma 150 - 500 is Angle of View 16.4 - 5.0 degrees
the sigma 300 - 800 has Angle of View 8.2 - 3.1 degrees
The canon 400d multiples focal lengths by 1.6 (nikon APS-c by 1.5) so the 120 to 400 is really 192 to 640.
I look forward to seeing your shots with this new lens as its on my list of "nice to haves" and id like to see if its really nice to have.
p.s. the canon Angle of view (horzntl, vertl, diagnl) is 29º - 6º 50', 19º 30' - 4º 35', 34º - 8º 15'
Surely on a Canon with 1.6x factor this lens has the equivalent of 192-640?
I've got the older 135-400 non OS (but APO) version and I can't tell much difference between it and my Sigma 70-300
Can i ask another question with the 400D you have 10MPixels and perhaps ISO usable up to 400 for your birds.
With a 550D/60D/7D you'd have twice the pixels and usable ISO upto (i'm guessing here) 1600?
This would mean for a similair cost to the lens you could instead buy a better sensor and digitally crop/zoom to 10MPixels from 18 Mpixels and with the extra ISO (ie faster shutter spreeds) perhaps get your birds in flight too? I only ask as its a question i'm wrestling with over my 400D, though i'm a generalist not an avarian tog.
I'm not sure if this though equates to a big improvement in the angle of view stakes.
I know where your coming from Jack but someone more experienced than me might be best answering that. Im interested in any replies on that too
Worth reading this thread
Jack, generally the law if diminishing returns hits as you add more pixels to a camera, and also as you add more pixels you make more demands on the lens. So a low cost lens heavily cropped is not a recipe for success. Re the 400D you should be able to get decent A4 prints at ISO1600 (Assuming it is like the 40D). Whilst it looks noisy on the screen it prints well. Plus it may be better to invest in a decent noise reduction piece of software like noiseware. It is amazing what can be saved. You do need to nail exposure etc correct at higher ISO or noise gets out of hand.
I can confirm that you can - I shot at ISO 1600 with my old 400D in Borneo at night in desparation, knowing the noise would be horrible but that without that, there was no shot at all. Sure enough, on the PC screen it was pretty noisy, but printed there was almost no noise at all. That was just using PS built in noise reduction, so the plug ins would give you an even better result I'm sure.
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