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# Question: How to calculate the FOCAL LENGTH

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 Question: How to calculate the FOCAL LENGTH on Jul 29, 2017 at 4:31:42 pm

Hi guys

I've taken two full HD video (1920,1080) with a nikon d750 with a full-frame sensor and an EOS 7D Mark II canon with a crop factor for compositing CG and live action.

First video made with Nikon d750, lens: 24-70 mm
Second video made with Canon EOS 7D Mark II, lens: 24-70 mm

How do I calculate the exact focal length of each Nikon camera and Canon with their respective sensors and have exact FL parameters for the virtual camera?

Are mathematical formulas specific to doing this?

The focal length of a lens is affected by the two different sensors?

I'm very confused.

 Re: Question: How to calculate the FOCAL LENGTHon Jul 30, 2017 at 4:45:47 pm

The crop factor of the APC sensor is 1.6x so multiply by 1.6.

24mm (full frame) x 1.6 = 38.4mm

Warren Eig
O 310-470-0905

email: info@babyboompictures.com
website: http://www.BabyBoomPictures.com

For Camera Accessories - Monitors and Batteries
website: http://www.EigRig.com

 Re: Question: How to calculate the FOCAL LENGTHon Jul 31, 2017 at 9:23:56 am

Hi, warren

Different articles say the focal length never changes, or with a full frame sensor or a crop factor sensor.

So,
Because, according to your calculation, the 24 mm with the APS sensor becomes 38.4?

 Re: Question: How to calculate the FOCAL LENGTHon Jul 31, 2017 at 4:48:27 pm

Yes, the the lens focal length is the same. A 50mm is a 50mm. But the FOV-- field of view changes. A 50mm on an APC sensor has a crop factor. That crop factor, 1.6 makes the 50mm an 80mm.

https://petapixel.com/2017/02/14/crop-factor-calculator-makes-sensor-math-b...

Warren Eig
O 310-470-0905

email: info@babyboompictures.com
website: http://www.BabyBoomPictures.com

For Camera Accessories - Monitors and Batteries
website: http://www.EigRig.com

 Re: Question: How to calculate the FOCAL LENGTHon Jul 31, 2017 at 8:27:39 pm

[Warren Eig] "That crop factor, 1.6 makes the 50mm an 80mm."

And this is why people are so confused on this point. The crop factor does not make the 50mm an 80mm. The width of the image on APS-C will be similar to an 80mm on a full-frame camera.

Think of focal length this way: each lens, due to the way the glass curves for each focal length, renders a scene a specific way. Most of the time, this will be very hard to see for the average consumer, but for someone who lives and breathes images, it will be more noticeable. The way the 50mm represents the world will always be the same, no matter what crop sensor you're on. The way the 80mm represents the world will also be different, and will remain the same way no matter the crop sensor.

The width between the two is what changes, nothing else.

 Re: Question: How to calculate the FOCAL LENGTHon Jul 31, 2017 at 8:33:02 pm

Actually, not quite. The field of view (FOV) changes, so that 50mm had more telephoto look on an APC-H sensor. That's why the manufacture calls it a crop factor.

Warren Eig
O 310-470-0905

email: info@babyboompictures.com
website: http://www.BabyBoomPictures.com

For Camera Accessories - Monitors and Batteries
website: http://www.EigRig.com

 Re: Question: How to calculate the FOCAL LENGTHon Aug 1, 2017 at 12:27:22 pm

Thanks to everyone for the answers

But in my particular case I do not need to calculate the focal length equivalent to 35 mm, which is simply a
comparison.

But the calculation to be made is the real length of the lens with the full frame sensor and the APS sensor (canon).

So,

The famous 24 mm or 70 mm lens with full frame sensor, what is it?

24mm or 70mm lens with the APS (canon) sensor, what is it?

 Re: Question: How to calculate the FOCAL LENGTHon Aug 2, 2017 at 1:55:53 am

[jack allegra] "The famous 24 mm or 70 mm lens with full frame sensor, what is it? 24mm or 70mm lens with the APS (canon) sensor, what is it?"

You already have more than enough information to calculate this.

 Re: Question: How to calculate the FOCAL LENGTHon Aug 2, 2017 at 6:50:01 am

(Gary Huff) "You already have more than enough information to calculate this."

This is not the case
I do not have enough information.
Because I still do not understand the concept.

So,
Can anyone answer precisely and clearly to the question below?

Grazie a tutti per le risposte

Ma nel mio caso particolare non ho bisogno di calcolare la lunghezza focale equivalente a 35 mm, che è semplicemente un
confronto.

Ma il calcolo da fare è la lunghezza reale dell'obiettivo con il sensore full frame e il sensore APS (canon).

Così,

la famosa lente da 24 mm o da 70 mm con sensore full frame, cos'è?

Obiettivo 24mm o 70mm con il sensore APS (canonico), che cosa è?

 Re: Question: How to calculate the FOCAL LENGTHon Aug 2, 2017 at 2:17:23 pmLast Edited By Gary Huff on Aug 3, 2017 at 2:09:35 pm

[jack allegra] "This is not the case. I do not have enough information. Because I still do not understand the concept."