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True Lens Focal Lengths??
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Nov 10, 2017 06:51:43   #
RWR Loc: La Mesa, CA
 
rgeremia1 wrote:
I was looking at comparisons review between Canon 100-400 Mark II vs a Canon 300f/4 with a 1.4 teleconverter attached and a Canon 400 f5.6 and the reviewer remarked that the 100-400 did not reach as far as the 400f 5.6. He believed it fell somewhere around 380mm fully extended. The reason I was even looking at the review was that I recently visited the Conowingo Dam and I was photographing the Eagles some of which flew over our heads so I retracted the lens but neglected to fully extend it after that a couple of times and it was not till I reviewed my photos that night that I realized how often I did this. ANYWAY I thought next time I might just lock the lens at it's total length and use my 70-200 for the close shots which led me to think about my 300 plus a tele which would give me 420mm. Long story for a short point, is there really such a mm lost with the 100-400?
I was looking at comparisons review between Canon ... (show quote)

You may find this interesting:
http://www.bobatkins.com/photography/technical/measuring_focal_length.html

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Nov 10, 2017 07:04:27   #
Retina Loc: Near Charleston,SC
 
rgeremia1 wrote:
I was looking at comparisons review between Canon 100-400 Mark II vs a Canon 300f/4 with a 1.4 teleconverter attached and a Canon 400 f5.6 and the reviewer remarked that the 100-400 did not reach as far as the 400f 5.6. He believed it fell somewhere around 380mm fully extended. The reason I was even looking at the review was that I recently visited the Conowingo Dam and I was photographing the Eagles some of which flew over our heads so I retracted the lens but neglected to fully extend it after that a couple of times and it was not till I reviewed my photos that night that I realized how often I did this. ANYWAY I thought next time I might just lock the lens at it's total length and use my 70-200 for the close shots which led me to think about my 300 plus a tele which would give me 420mm. Long story for a short point, is there really such a mm lost with the 100-400?
I was looking at comparisons review between Canon ... (show quote)

I don’t think of the nominal range of a zoom lens as a precise spec, but do expect a reasonably equivalent field of coverage when compare to the same length prime. Maybe the 400mm prime is rounded down from 406.7 and the extended zoom is 395.6 making them close enough to round fairly but showing a real difference in operation. Aren’t there also slight differences among models of the same sensor class in the actual dimensions of the area of a sensor that is used for the image? If so, it would make accurate labeling in terms of what a buyer should expect very difficult. A chart including different bodies would be needed, and few would care. If anyone has a few Canon crop cameras from different series or lines over time, maybe they would see slight differences in their respective fields of coverage making it appear the lens has a different FL depending on the body, even the we know FL has nothing to do with the body per se. In other words, I don’t believe most photographers care about the precise distance between the plane of focus and some plane within a complex multi-element lens when focused at infinity, but rather what part of a scene is captured ehen compared with a prime of the same nominal length on the same camera. I would allow manufactures to fudge a bit for these reasons and more. I am not an optical engineer, so I welcome corrections from those who know these things. It doesn’t have much to do directly with taking good pictures, but they do matter at some level to some of us based on the question. I apologize for the length.

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Nov 10, 2017 08:16:12   #
Notorious T.O.D. Loc: Harrisburg, North Carolina
 
You might find these lens reviews interesting...

http://www.grantatkinson.com/blog/lens-reviews

By a real user of the lenses...

Best,
Todd Ferguson

rgeremia1 wrote:
I was looking at comparisons review between Canon 100-400 Mark II vs a Canon 300f/4 with a 1.4 teleconverter attached and a Canon 400 f5.6 and the reviewer remarked that the 100-400 did not reach as far as the 400f 5.6. He believed it fell somewhere around 380mm fully extended. The reason I was even looking at the review was that I recently visited the Conowingo Dam and I was photographing the Eagles some of which flew over our heads so I retracted the lens but neglected to fully extend it after that a couple of times and it was not till I reviewed my photos that night that I realized how often I did this. ANYWAY I thought next time I might just lock the lens at it's total length and use my 70-200 for the close shots which led me to think about my 300 plus a tele which would give me 420mm. Long story for a short point, is there really such a mm lost with the 100-400?
I was looking at comparisons review between Canon ... (show quote)

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Nov 10, 2017 12:20:33   #
whitewolfowner
 
rgeremia1 wrote:
I was looking at comparisons review between Canon 100-400 Mark II vs a Canon 300f/4 with a 1.4 teleconverter attached and a Canon 400 f5.6 and the reviewer remarked that the 100-400 did not reach as far as the 400f 5.6. He believed it fell somewhere around 380mm fully extended. The reason I was even looking at the review was that I recently visited the Conowingo Dam and I was photographing the Eagles some of which flew over our heads so I retracted the lens but neglected to fully extend it after that a couple of times and it was not till I reviewed my photos that night that I realized how often I did this. ANYWAY I thought next time I might just lock the lens at it's total length and use my 70-200 for the close shots which led me to think about my 300 plus a tele which would give me 420mm. Long story for a short point, is there really such a mm lost with the 100-400?
I was looking at comparisons review between Canon ... (show quote)


Not every lens that says its range is from here to there is actually that range but close to it. Imagine a lens saying it's 113-378mm, instead of 100-400mm. Everyone would think them crazy for making it and never buy it. So they design a lens to be in a class of lenses that are already out there and accepted. They get them as close to those ranges as possible but I'm sure many times lens design creates limits that are impossible to hurtle over or too expensive to get them there.

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Nov 10, 2017 14:10:20   #
amfoto1 Loc: San Jose, Calif. USA
 
Very few lenses are PRECISELY the focal length they're marked. In nearly all cases the focal length is rounded off for marketing purposes (usually in the manufacturer's favor).

There is allowance for as much as +/- 5% or 10% variation from what's marked.

I couldn't find the patent or a lab test giving the precise focal lengths of the Canon 100-400mm II specifically, but some other examples include:

- Canon EF 24-105mm f/4L II IS USM (patent filed 2016).... actual focal lengths 24.70 to 102.11mm.

- Tamron 100-400mm VC (patent, 2016).... actual focal lengths 103.00 to 389.05mm.

- Canon EF 1000mm f/5.6 DO (patent, 2016).... actual focal length 950mm (only a patent filing, not yet produced).

- Sigma 24-70mm f/2.8 OS HSM Art (patent, 2016)... actual focal lengths 24.85 to 68.00mm.

- Sigma 20mm f/1.8 DG HSM (patent, 2016)... actual focal length 20.70 to 21.01mm (not a zoom, this prime lens has focus breathing)

- Canon EF-S 10-20mm f/4.5-5.6 IS STM (patent, Feb. 2015).... actual focal lengths 9.50 to 19.70mm (lens not produced, instead an EF-S 10-18mm STM is avail.)

- Canon EF 16-35mm f/2.8L III USM (patent, Oct. 2014).... actual focal lengths 16.49 to 33.94mm.

Seriously, would you buy a zoom labelled "16.49-33.94mm"? Or would you prefer a "16-35mm"?

P.S. The same is actually true of lenses' f-stop ratings... there's always some slight variation in those, too.

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Nov 10, 2017 14:11:13   #
rgeremia
 
Thank you SS, I do like the ability of finding a BIF and then zooming in for the photo. I need to be more diligent in monitoring the length of my zoom when I DO shoot It sounds so simple but in the excitement capturing an Eagle going in for the kill I messed up a couple of times. Practice, Practice, Practice!

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Nov 10, 2017 14:15:02   #
rgeremia
 
Amfoto1,
This is great information for all of us. Thanks so much. BG

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Nov 10, 2017 18:32:55   #
imagemeister Loc: mid east Florida
 
Probably next week, a friend of mine and I will be using the Canon 80D testing the Canon 70-200 2.8II W/2X, the 100-400 G1, the 100-400 G2, the 400 5.6 prime, and with 1.4X, and the Sigma 100-300 f4, and W/1.4X, and the Sigma 100-300 f4 W/ Clear Image Zoom on the Sony A77II. - stay tuned ........

and we might throw in the Canon 70-300 IS II nano - just because we can ......

..

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Nov 10, 2017 19:16:50   #
Notorious T.O.D. Loc: Harrisburg, North Carolina
 
Sounds like a lot of testing but interesting. Keep us posted...

Best,
Todd Ferguson

imagemeister wrote:
Probably next week, a friend of mine and I will be using the Canon 80D testing the Canon 70-200 2.8II W/2X, the 100-400 G1, the 100-400 G2, the 400 5.6 prime, and with 1.4X, and the Sigma 100-300 f4, and W/1.4X, and the Sigma 100-300 f4 W/ Clear Image Zoom on the Sony A77II. - stay tuned ........

and we might throw in the Canon 70-300 IS II nano - just because we can ......

..

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