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For those in love with the FULL FRAME look which system gets closest in 4K?

Andrew Reid

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@Andrew Reid NX1 (NX mount) is seeing a prototype of a speedbooster with a 1.1 crop in effect.

You can find the project in your sticky NX1 topic. One of your forum members is developing this piece of tech.


Btw, beautifl article.


"When the sensor is physically already smaller than full frame, any further crop employed in 4K is added to that base crop (for example 1.5x for the APS-C Fuji X-T2 plus a further 1.17x crop in UHD 4K)."


Would you like to add a sentence to your article about the simple math of calculating the resulting crop out of sensor crop and additional 4K crop?

For instance for Fuji XT2:

1.5 APC-crop * 1.17 additonal 4K crop = 1.75 total crop for 4K


That way the simple math would be explicitely written done for every seeking soul.




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17 minutes ago, Bill Sepaniak said:

I use a Speedbooster Ultra on my A7RII in Super 35. Super 35 image quality and I get what amounts to FF when using my MF Contax/Zeiss MF lenses + gaining a stop ... so a little better low light capability. 

Or save a wedge and use the A6300? I suppose you get the sensor stabilisation with the A7 series.

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Timely article Andrew. I believe the Metabones XL only increases aperture by 1 & 1/3 stop, not the one and half stop faster F-stop you mention in the article.

In terms of 35mm equivalent focal length, I get that a Canon EF 70-200mm f/2.8L would become an effective 90-256mm on a standard MFT camera with XL adapter, but what about an APSC lens like the Sigma 18-35mm f/1.8 DC HSM? B&H claim this lens has a 35mm Equivalent Focal Length of 28.8-56mm so is there more to calculate the 35mm equivalent when used on MFT with XL adapter?

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Andrew, just for my understanding. Your key sentence for me was: “. . . when we refer to full frame video, we only take into account the horizontal crop and take the different aspect ratio for granted.”

In the case for the actual GH4 it means:  

GH4 Sensor:           4608:3456 (4:3)

GH4 QFHD:            3840:2160 (16:9) which is 52% of the GH4 sensor area.

For the upcoming GH5 “full sensor readout” has been announced. Taken the same sensor dimensions into account it will then use 4608 horizontal Pixels for 16:9 4k video, which means 4608:2592 pixels are used: This is  75% of the sensor area. As result, the new GH5 will use 50% more of the sensor area, but - of course - per se it can’t be “true” 100% full sensor readout  for video.  

I know, everybody has understood this except me. Sometimes it needs post like yours, Andrew, to understand basics, at least for me. Thanks.

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2 hours ago, Jonesy Jones said:

My understanding is that Red Helium is not 'full frame', it is Super 35. Red used a smaller pixel density to get 8K onto an S35 sensor.

Yea...you're right... it is red dragon 8k I'm thinking of.

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7 hours ago, Andrew Reid said:


The video crop factors of the current 4K cameras, and an easy way to calculate crop factors...

Read the full article

Crop Factor is based in the Image Circle, that's why the diagonal is used instead of the width. The diagonal is based on the video mode not stills mode (entire sensor), so it's a little more work to compute the Crop Factor. Your math is indeed simpler, unfortunately it will lead to confusion since it's not actually the Crop Factor. You could call it Width Ratio or similar to let people know it's not the image circle diameter ratio and not the actual Crop Factor.

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Dear Andrew,

thank you very much for your post, that is very useful to clarify what the crop factor is, while in the web there is a big confusion.

However I’m a bit disappointed you didn’t mention NX1 in your article, whereas this superb camera is living a second life beyond the official “death” also thanks to the great passion of some members of your forum.


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I read somewhere else that the UHD crop for the G7 is 2.2 , which sounds great compared to 2.4 on the GH4. (If what I read was the same maths)

The G7 has a £100 cashback deal in UK at the moment, so it is a very affordable option (£299 from Wilkinson Cameras).

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