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10-14-2008, 09:02 AM   #1
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Confused

hello there

i just bought the fa 43mm f/1.9 ltd, and i'm wondering about its focal lenght. i read somewhere that on digital, its not 43mm, because of a different format or something. say - what does the 43mm equal then, compared to the 18-55 kit? does 43mm on the kit lens equal the same focal lenght as the 43mm f/1.9, or?

thanks

10-14-2008, 09:13 AM   #2
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QuoteOriginally posted by Lovold Quote
hello there

i just bought the fa 43mm f/1.9 ltd, and i'm wondering about its focal lenght. i read somewhere that on digital, its not 43mm, because of a different format or something. say - what does the 43mm equal then, compared to the 18-55 kit? does 43mm on the kit lens equal the same focal lenght as the 43mm f/1.9, or?

thanks
It's 43mm on digital too and exactly the same as 43mm on your kit lens. The field of view equals to 64,5mm on full frame (35mm) slr due to smaller sensor. The focal lenght will never change when the format does (aps-c sensor vs. full frame), just the field of view. Think of it as a crop.
10-14-2008, 09:18 AM   #3
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Okay, thanks for clearing that up!
10-14-2008, 10:20 AM   #4
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At closer focus distances the 43 will be a little tighter than the zoom at 43mm though.

10-14-2008, 05:17 PM   #5
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This is why I cringe over the whole crop factor thing.
Learn to use your lenses for what they are on the format you are using them on rather than what they are on a format you are not using them on, and your life will be much happier.
10-14-2008, 05:25 PM   #6
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QuoteOriginally posted by Wheatfield Quote
This is why I cringe over the whole crop factor thing.
Learn to use your lenses for what they are on the format you are using them on rather than what they are on a format you are not using them on, and your life will be much happier.
Well said, composing and taking the shot should be the fun part.
10-14-2008, 08:29 PM   #7
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Stuff I learnt on this forum that I did not know when i moved to a DSLR


* The rull of thumb for a hand held shot is not the inverse of the focal length, but rather the inverse of the aparrent focal length. so, for a 50mm, it is 1/80s not 1/50s
* perspective has nothing to do with focal length. it has to do with distance to the subjuct. A 50mm lens on a FF camera, will have the same camera to subject distance as a 33mm lens (or 31mm, or 28mm), and will have the same perspective characteristics.
* Hyperfocal distances are different. That is all I am going to say. The topic hurts my brain, and I ignore it. I just use the FF settings.
10-15-2008, 03:15 AM   #8
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Sorry, I probably phrased myself wrong. What I meant was that if the field of view equalled a higher focal length. I.e. field of view on 43mm f/1.9 is tighter than field of view on 43mm on the kit lens. I didn't mean to say that the focal lenght magically changed, it was the field of view I was referring to, sorry for confusing you (a bit confused myself).

10-15-2008, 05:22 AM   #9
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QuoteOriginally posted by Lovold Quote
I.e. field of view on 43mm f/1.9 is tighter than field of view on 43mm on the kit lens.
Yes slightly, I alluded to this above. Because the zoom is a zoom it will lose magnification as you zoom out. By 43mm though it's bugger all difference.
10-15-2008, 05:34 AM   #10
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we seem to have 2 things being mixed in this thread so I will address them separately.

first of all, and excuse the mild rant, I am getting totally p&**^*&^ at the whole industry, not just people here continuing on about focal length equivelents. Every magazine I read continues this BS. Focal length is focal length, it is a physical property. Lets move on.

OK rant finished, lets look at the second issue, that being focal length of zooms.

Although I had not noticed this, and it is not properly published in magazines when they test lenses, I have now seen several threads and articles about the fact that on many zoom lenses the focal length range is only accurate when focused to infinity, and as you focus in, you also change the focal length.

This may explain your field of view of a 43mm vs a zoom at 43mm. To be clear, the definition of focal length is actually the distance from a focusing screen when an object is at infinity. Even with a prime lens, the field of view will change when focusing closer, but I believe the internal focusing of the zooms must be much more radical than a prime
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