Daniel Haggett

London based Lighting Cameraman / DoP 

Lens comparison and crop factors

Firstly, before getting into this a word of caution. Using the idea of a "crop factor" is slightly tricky, as to have a crop factor you need a reference guide, from which perspective all other sensor sizes are cropped.  With the advent of DSLR filming and "full frame" 5d and 1d some people talk of all other smaller sensor sizes as being cropped.  However, the  smaller sensor size of Super 35 has been a standard in the film industry for years.  For example, when working on an Arri Alexa most people from a film and TV background don't think of a 50mm lens as having the field of vision of a 70mm lens as it has been "cropped into", for them a 50mm lens is a 50mm lens on an Alexa and they are not comparing it to the image you would get on a 36 x 24mm full frame sensor such as the 5d or 1d.

 

Having said this, so many people are using this crop factor as compared to the 35mm full frame chip that I will continue to use this as a reference guide here.

 

Firstly the cameras. 

35mm Full Frame: 

sensor size: 36x24mm

Canon  5D and 1D


Super 35mm chip: 

Sensor Size 24.9 x14mm (these have a crop factor of around 1.4 to 1.5 as compared to full frame cameras although sensor size varies slightly in this group)

Red Epic, Scarlet  (25.9 x 14.5)

Canon C300 C100 C500  (24.6 x13.8mm)

Arri Alexa (23.8 x 13.4mm)

Sony F65/F3, FS100, FS700  (23.6 x13.3)

Sony F55 F5 (22.6 x12.7mm)

 

APS-C chip:

Sensor size 22.2x14.8 crop factor of 1.6

Canon 7d, 60d, 50d (22.2x14.8mm)

 

4/3 inch chip:

sensor size: 17.8 x 10 crop factor of 2

Panasonic AF101

 

Blackmagic design camera

sensor size: 15.8 x 8.9 mm

Blackmagic


2/3 inch chip:

Sensor size: 8.8 x 6.6mm   cameras have a crop factor of around 4x

Sony XDCAM 700/800 

Panasonic AJ-HPX3000

Most other traditional ENG style broadcast cameras.

 

In the image below, I have illustrated each sensor size as a comparison tool.  This image is 4 x the sensors actual size, so that the relative differences are easier to see.  As you can see, the difference between the yellow from the 7d to the red Super 35 is small even at 4x.  This is somewhat confusing as the actual sensors don't have the same aspect ratio, as they are also used for 4:3 recording or photos in the case of the stills cameras.  (To see the changes to the field of vision when in movie recording mode, see the next picture.)

video sensor size comparison 

This next image demonstrates the relative field of vision you would get from each sensor.  All of these are now 16:9 as the stills camera would be shooting in video mode at this aspect.

alt

 

With the advent of new 4k technology, cameras such as the Sony F55 / F5 are able to shoot at 2k using a crop of their own sensor.  The great thing about that is it opens up the possibility of using lenses designed for smaller sensors or film.  The centre crop mode on the F55/5 will allow you to use 16mm lenses, and there are some amazing 16mm lenses out there which are incredibly cheap.  I haven't tried using one of these on an F55, but my guess is that if it works well they won't be cheap for much longer.

Since there is a massive difference in the crop factor of 2/3 inch cameras and single chip cameras, I thought I'd write up a few lens range comparisons.  Many of us are used to working with Canon broadcast lenses such as HJ11, HJ22 etc, and since these are designed for B4 mount, 3 chip cameras the crop factor is pretty large.  Here are a few notes on how different lenses compare.

 

Lens size

2/3 inch 4x crop  Effective Focal Length

HJ11: 4.7 - 52mm

With doubler 9.4-104mm

HJ22: 7.6~168mm

with doubler 15~336mm

18.8mm to 208mm

37.6mm - 415mm

30mm - 672mm

doubler 121 - 1,462mm

 

This next table illustrates the difference between a full frame camera and a APS-C chip camera such as a 7d. 

 

 

Full Frame no crop

1.6 crop  effective focal length

(NB super 35 chip cameras will be very slighly wider here)

8-15mm

16-35mm

17-40mm

24mm

28mm

50mm

24-70mm

24-105mm

70-200mm

70-200mm with 1.4 extender 98- 280mm

70-200 with 2x extender 140-400

13-24mm

26-56mm

27-64mm

38mm

45mm

80mm

38-112mm

38-168mm

112- 320mm

157-448mm

224-800mm

Interestingly the HJ 11 full focal range is 19mm to 415mm (including the doubler) so if you wanted to have the same focal range using a single chip camera with eos lenses, you would need pretty much every eos lenses they make.

It is possible to use B4 mount broadcast lenses on single chip cameras with a B4 to EOS or PL adapter from MTF.  Since Super 35 sensor cameras have such a large chip compared to the broadcast cameras, the lenses will only work with the doubler on (otherwise you would have a massive vignette.)   I have done this a few times, although I am not a massive fan of it as you are obviously shooting through a layer of doubler glass and the optics aren't that great, although in terms of practicalities it does work.  MTF make a good variety of adapters, which you can buy from B&H. 

This is the range such lenses would give you on a super 35 chip camera:

HJ11 = 15-166mm

HJ22 = 24- 538mm

 

For further reading:

Abel Cine have created a useful comparisson showing all of the main camera sensors field of vision as compaired to super 35mm

Also from Abel Cine is an intersting tool that automatically calculates the field of vision on any lens size you choose from most of the major cameras in use.