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Andrew Reid

1.74x - A Crop Odyssey - Canon 5D Mark IV officially announced

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7 minutes ago, Andrew Reid said:

If it were measured only horizontally then you could have a weirdly extreme letterbox aspect ratio and call it 1.0x crop if it measured the full width of the sensor, so that can't be how they calculate it surely?

Full sensor area of the 5D Mark IV is 3:2

Measuring horizontally and diagonally gives you exactly the same results, 1.64 on 5D Mark IV.

HD mode would be 1.0x crop (6720/6720=1) because the camera is using/pixel-binning from the entire 16:9 area of the sensor.

Does 5D Mark IV shoot 3:2 video? No. So you measure the corresponding area using video aspect ratio when you calculate crop factor, in this case, 17:9 and 16:9.

See my edited post for more examples.

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16 minutes ago, Luke Mason said:

It IS measured horizontally. It ALSO works if you measure diagonally, let me do the math for you:

A DCI 17:9 full sensor area would be 6720x3454, using Pythagorean Theorem you can calculate that the diagonal pixel count is ~7597

the diagonal pixel count of a DCI 17:9 4096x2160 crop area is ~4631

7597/4631 = ~1.64

 

That's probably correct.

But you don't need the diagonal though, you just have to adjust the 6720x4480 from 3:2 to 4K aspect ratio, which would give something like 6720x3543 and then you can apply to any of the sides - or even the diagonal if you want. I used 3543 instead because 4096:2160 (1,896) is not exactly 17:9 (1,888), but it works anyway.

6720:4096=1,64

3543:2160=1,64

7597:4630=1,64

 

 

 

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1 minute ago, Luke Mason said:

Does 5D Mark IV shoot 3:2 video? No. So you measure the corresponding area using video aspect ratio when you calculate crop factor, in this case, 17:9 and 16:9.

No but to keep things consistent with other cameras sporting different aspect ratios, it's the total sensor crop that matters not the crop from a letterbox 16:9 of the sensor

For instance Micro Four Thirds is a 4:3 2x crop of a 3:2 full frame sensor

Therefore to make the comparison worthy, 5D Mk IV 4K video is a 1.74x crop of the same

Unless we stop talking about Micro Four Thirds 16:9 video as a 2x crop? But I feel that horse has somewhat bolted!

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Just now, theSUBVERSIVE said:

That's probably correct.

But you don't need the diagonal though, you just have to adjust the 6720x4480 from 3:2 to 4K aspect ratio, which would give something like 6720x3543 and then you can apply to any of the sides - or even the diagonal if you want.

6720:4096=1,64

3543:2160=1,64

7597:4631=1,64

 

 

 

You don't even need to adjust the aspect ratio, just use the horizontal pixel 6720/4096 = ~1.64.

I was trying to demostrate to Andrew that both work and give the same result, seems like someone skipped a lot of math class lol.

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I did skip maths class, it's fucking uninteresting. I am more interested in images

But it is 1.74x crop from the full 3:2 sensor as Micro Four Thirds is a 2x crop from the same, so the 1.64 I can't accept, as it is measured from a different area to all the other cameras on the market

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1 minute ago, Luke Mason said:

You don't even need to adjust the aspect ratio, just use the horizontal pixel 6720/4096 = ~1.64.

I was trying to demostrate to Andrew that both work and give the same result, seems like someone skipped a lot of math class lol.

I did just to show that as long as it's the right aspect ratio you can use any measure.

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4 minutes ago, Andrew Reid said:

No but to keep things consistent with other cameras sporting different aspect ratios, it's the total sensor crop that matters not the crop from a letterbox 16:9 of the sensor

For instance Micro Four Thirds is a 4:3 2x crop of a 3:2 full frame sensor

Therefore to make the comparison worthy, 5D Mk IV 4K video is a 1.74x crop of the same

Unless we stop talking about Micro Four Thirds 16:9 video as a 2x crop? But I feel that horse has somewhat bolted!

I'm afraid your understanding of crop factor is completely wrong, M4/3 sensor is 17.3mm wide, FF is 36mm wide, 36/17.3 = ~2.1x crop.

You always use horizontal dimension to calculate crop factor.

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Just now, OliKMIA said:

Whatever guys, 1.64 or 1.74 is just useless anyway, 0.1 difference is not going to matter at this point.

It's a perfect Super 35mm crop, same size as many other cinema cameras. Some people don't like it and prefer FF look, but it's definitely not useless.

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6 minutes ago, Luke Mason said:

I'm afraid your understanding of crop factor is completely wrong, M4/3 sensor is 17.3mm wide, FF is 36mm wide, 36/17.3 = ~2.1x crop.

They simply measure the diagonal, regardless of the aspect ratio.

FF: 43.3mm

APS-C: 28.4mm (1.52x crop)

Canon APS-C: 26.7mm (1.62x crop)

Micro4/3: 21.6mm (2.00x crop)

 

Which means that the 5D MKIV is basically like a Canon APS-C 4K, so you can use APS-C EF lenses on it.

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Ok. So on my 24-70:

1.64 crop = 39-114mm

1.74 crop = 42-121mm


Looks very similar to me. When shooting events, traveling and so on I don't want to switch back and forth between a 24-70 and 16-35 or 11-24... Have to carry many lenses to fit a normal focal range.

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1 minute ago, theSUBVERSIVE said:

They simply measure the diagonal, regardless of the aspect ratio.

FF diagonal: 43.3mm

APS-C diagonal: 28.4mm (1.52x crop)

Canon APS-C: 26.7mm (1.62x crop)

Micro4/3: 21.6mm (2.00x crop)

For pure sensor size comparison, yes.

But hey man, we are talking about video mode with different aspect ratios.

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39 minutes ago, Andrew Reid said:

The crop is measured diagonally not just horizontally

4480/2160 = 2.07x

The maths after that I can't be too precise about but I guess it is an average of 1.64x and 2.07x so somewhere in the middle.

Sensor .. 6720 x 4480
4K .. 4096 x 2160

Sensor diagonal = 8076.43 .. i.e. sqrt of (6720^2 + 4480^2)
4K crop diagonal = 4630.64 .. i.e. sqrt of (4096^2 + 2160^2)

 Sensor diagonal/4K crop diagonal = 1.74 .. i.e. 8076.43/4360.64 = 1.74.

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3 minutes ago, Jn- said:

Sensor .. 6720 x 4480
4K .. 4096 x 2160

Sensor diagonal = 8076.43 .. i.e. sqrt of (6720^2 + 4480^2)
4K crop diagonal = 4630.64 .. i.e. sqrt of (4096^2 + 2160^2)

 Sensor diagonal/4K crop diagonal = 1.74 .. i.e. 8076.43/4360.64 = 1.74.

Sensor is 3:2, 4K is 17:9, you need to calculate using a 17:9 area of the sensor which is 6720x3454

sqrt of 6720^2 + 3454^2 = ~7597

7597/4631 = ~1.64

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14 minutes ago, Jn- said:

Sensor .. 6720 x 4480
4K .. 4096 x 2160

Sensor diagonal = 8076.43 .. i.e. sqrt of (6720^2 + 4480^2)
4K crop diagonal = 4630.64 .. i.e. sqrt of (4096^2 + 2160^2)

 Sensor diagonal/4K crop diagonal = 1.74 .. i.e. 8076.43/4360.64 = 1.74.

The full height of the sensor is not used, the aspect ratio of the sensor is 3:2 or 1.5. The aspect ratio used for 4K DCI is 4096/2160=1.896:

Sensor resolution for full frame video: 6720 x (6720/1.896) or 6720 x 3544

4K crop diagonal.. i.e. sqrt of (6720^2 + 3543.75^2)

sqrt(6720^2 + 3543.75^2)/4630.64 = 1.64x

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4 minutes ago, Luke Mason said:

Sensor is 3:2, 4K is 17:9, you need to calculate using a 17:9 area of the sensor which is 6720x3454

sqrt of 6720^2 + 3454^2 = ~7597

7597/4631 = ~1.64

1.64 crop doesn`t look too bad……..totally usable after all….but the codec is going to hurt anyway.

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3 minutes ago, hijodeibn said:

1.64 crop doesn`t look too bad……..totally usable after all….but the codec is going to hurt anyway.

Hurt only in terms of storage space, MJPEG codec @ 500Mbps and 4:2:2 is actually a very high quality codec, the best codec among DSLRs and the only 422 codec used apart from cinema cameras.

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7 minutes ago, Luke Mason said:

Hurt only in terms of storage space, MJPEG codec @ 500Mbps and 4:2:2 is actually a very high quality codec, the best codec among DSLRs and the only 422 codec used apart from cinema cameras.

That's what i mean, storage, but if the quality is good enough could be worthy, anyone has a video example in this codec?

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5 minutes ago, Luke Mason said:

Hurt only in terms of storage space, MJPEG codec @ 500Mbps and 4:2:2 is actually a very high quality codec, the best codec among DSLRs and the only 422 codec used apart from cinema cameras.

I've taken the liberty of using this extract from an article in Photography Life, he explains it a lot better than I could ...

I simply replaced sensor dimensions, which would be in millimetres i.e. 24x36 for FF with 4480x6720 and xx x yy for 2160 x 4096.

https://photographylife.com/what-is-crop-factor
"How Crop Factor is Calculated
The math to derive the crop factor is quite simple. Knowing the physical size of the sensor, you first calculate the diagonal using Pythagorean Theorem (a² + b² = c²), then divide the number by the diagonal of the crop sensor."

I personally don't have any problem if it is 1.64, all the better, since i've already ordered it, but using the diagonals of the FF sensor and the diagonal of the 4K crop it's 1.74.

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