GH2 crop factor 1.86x or 2x ?

[daveswan]

Aargh!

Aspect ratios ... field of view .... cropped....stop before my brain explodes!

One way out is to consider that the eye preferentially scans a scene from side to side, therefore we could measure the width of the sensor to work out the angle that any given lens will give on a particular sensor.

So, for a lens whose FL is the same (Or similar) to the width of the sensor, a 35mm lens on FF is a similar FOV to about 22mm on APS C or 18 on GH2 (Wider than 4/3), or, for that matter 240mm on my 10x8 monorail

These are, of course, very rough figures, you can supply the decimal points yourselves

 

[Ian-T]

To the OP: It's 1.8596 I believe which basically rounds to 1.86.

As already mentioned the GH-1/2 has this weird type of M4/3 sensor which is a little bigger than typical M4/3 sensors (the AF100 is a typical M4/3 sensor).

APS-C (Canon 7D/T2i etc.) has a 1.6 crop factor in video mode. Why so close? Well because those cameras "crop" thier (square) sensor to get that (rectangular)16:9 image we all know in video mode. But the GH-1/2 uses every bit of its oversised (rectangular) sensor to get the same (rectangular) 16:9 image. The APS-C is still bigger in the end...but as you can see....just barely.

Even the 5Dll crops its square sensor to get its 16:9 video (not STILLS) image.

So when people are talking about crop this or crop that....I think the first question one should clarify is...."are we talking STILLS or are we talking VIDEO?" There is a huge difference. Remember...whether STILLS or VIDEO the GH-1/2 numbers will stay "around" the same but with other "SQUARE" sensored cameras (like the 5Dll's 3:2 or the APS-C ) there is a big difference between the two formats (video=cropped and stills=not). That alone would change how one can compare between these cameras.

Kinda what cbrandin is saying above.

 

[Guest]

Surprised by all the debate on this subject. I really didn't see that coming! haha! Happy New Year to all!

 

[notharrylume]

Angels on the head of a pin.

 

[dcloud]

For video crop compared to S35:AF100 under HDSLRhttp://www.abelcine.com/fov/May or may not be exactly the same as the GH2, but close enough.

Not the same. As said before af100's sensor is closer to 2x bec its not an oversized sensor

 

[dcloud]

You just said it's 1.86 and then in your next post you say you don't know? I'm confused. Regardless, whether it's 2.0, 2.1, or 1.86 when compared to the 5D, it doesn't matter because we shouldn't be comparing it to the 5D for video. The 5D is the exception, not the rule. Compare to S35 16x9 film, which would make it a 1.4x crop if it's a normal 4/3 sensor, or even less than 1.4x if it's actually larger than a regular 4/3 sensor. I wasn't aware the GH2 has a slightly larger sensor than a regular 4/3 sensor. Would be nice for clarification on the size of the GH2 and AF100 sensors when shooting 16x9 video so we can get an accurate crop factor when compared to S35 16x9 film.

I meant i dont know if its exactly 1.86 or whats the decimal. Apparently its 1.859 as said by kholi. Now what kholi said is accurate and is what we discussed long time ago and he answerd all youre questions

 

[Mike@AF]

Using the actual dimensions of the GH2 and AF100 sensors when shooting 16x9 video, here's the correct crop factors against various cameras.

[TD="bgcolor: #eaeaea"]
[/TD]
[TD="bgcolor: #eaeaea"]

Sensor Image Diagonal (mm)​

[/TD]
[TD="bgcolor: #eaeaea"]

GH2 Crop Factor​

[/TD]
[TD="bgcolor: #eaeaea"]

AF100 Crop Factor​

[/TD]

[TD="bgcolor: #eaeaea"] Super 35 Film 16x9 [/TD]
[TD="bgcolor: #eaeaea"]

28.5​

[/TD]
[TD="bgcolor: #eaeaea"]

1.3​

[/TD]
[TD="bgcolor: #eaeaea"]

1.4​

[/TD]

[TD="bgcolor: #eaeaea"] Super 16 Film 16x9 [/TD]
[TD="bgcolor: #eaeaea"]

13.7​

[/TD]
[TD="bgcolor: #eaeaea"]

0.6​

[/TD]
[TD="bgcolor: #eaeaea"]

0.7​

[/TD]

[TD="bgcolor: #eaeaea"] Arri Alexa [/TD]
[TD="bgcolor: #eaeaea"]

27.8​

[/TD]
[TD="bgcolor: #eaeaea"]

1.3​

[/TD]
[TD="bgcolor: #eaeaea"]

1.4​

[/TD]

[TD="bgcolor: #eaeaea"] Sony F3/FS100/F35 [/TD]
[TD="bgcolor: #eaeaea"]

27.1​

[/TD]
[TD="bgcolor: #eaeaea"]

1.3​

[/TD]
[TD="bgcolor: #eaeaea"]

1.3​

[/TD]

[TD="bgcolor: #eaeaea"] Red One/Scarlet 4K [/TD]
[TD="bgcolor: #eaeaea"]

25.4​

[/TD]
[TD="bgcolor: #eaeaea"]

1.2​

[/TD]
[TD="bgcolor: #eaeaea"]

1.3​

[/TD]

[TD="bgcolor: #eaeaea"] Red Epic 5K [/TD]
[TD="bgcolor: #eaeaea"]

29.7​

[/TD]
[TD="bgcolor: #eaeaea"]

1.4​

[/TD]
[TD="bgcolor: #eaeaea"]

1.5​

[/TD]

[TD="bgcolor: #eaeaea"] Panasonic AF100 [/TD]
[TD="bgcolor: #eaeaea"]

20.1​

[/TD]
[TD="bgcolor: #eaeaea"]

0.9​

[/TD]
[TD="bgcolor: #eaeaea"]

1.0​

[/TD]

[TD="bgcolor: #eaeaea"] Canon 5Dmk2 [/TD]
[TD="bgcolor: #eaeaea"]

41.3​

[/TD]
[TD="bgcolor: #eaeaea"]

1.9​

[/TD]
[TD="bgcolor: #eaeaea"]

2.1​

[/TD]

[TD="bgcolor: #eaeaea"] Canon 7D [/TD]
[TD="bgcolor: #eaeaea"]

26.8​

[/TD]
[TD="bgcolor: #eaeaea"]

1.2​

[/TD]
[TD="bgcolor: #eaeaea"]

1.3​

[/TD]

[TD="bgcolor: #eaeaea"] Panasonic GH2 [/TD]
[TD="bgcolor: #eaeaea"]

21.6​

[/TD]
[TD="bgcolor: #eaeaea"]

1.0​

[/TD]
[TD="bgcolor: #eaeaea"]

1.1​

[/TD]

I used Abel Cine's measurements for all other diagonals, which are all rounded to tenths, so I kept all calculations to tenths for consistency.

Again, I will say that the proper comparison for crop factor should be with Super 35 film as that is the standard for filmmaking and has been for many years. The 5D is the exception, not the rule. Use 5D for stills comparison. Use Super 35 for film/video comparison.

 

[AGMedia]

Nice job on that chart Mike@AF! Those are comforting numbers for GH2 owners.

Your point about "Super 35" film is good and logical.

I would respectfully respond that field of view is a secondary issue to low light -- and that the main advantage of bigger sensors/pixels is better sensitivity to light. In a general sense this means less lighting headaches for users in the field and vastly more creative options.

The 5Dm2 isn't going to be the exception for much longer. At least two of the next headlining DSLRs from Canon will have full frame sensors, and at least one (probably two) from Nikon. The 1Dx is producing CLEAN video at ISO 25,000 -- and that's the real point of the larger sensor.

But -- the GH2 is still a great little camera -- and with stable 100 Mbit mpeg-4 intraframe -- I'd buy a GH2 before I'd buy an AF100. And -- with stable 100 Mbit mpeg-4 intraframe recorded to cheap media in a camera I can fit in my jacket -- I find "crop factor" less of a headache.

Again, Mike, thanks for putting together that chart.

 

[Barry_Green]

As said before af100's sensor is closer to 2x bec its not an oversized sensor

Yes it is. Four Thirds is 17.3mm wide. The AF100 is 17.8mm wide.

The spec for the GH2 has never been released, but we kind of back-calculated it to be 18.9mm based on the number of quoted pixels on the chip overall, and the number of pixels used in each of its modes.

 

[M. Gilden]

Again, I will say that the proper comparison for crop factor should be with Super 35 film as that is the standard for filmmaking and has been for many years. The 5D is the exception, not the rule. Use 5D for stills comparison. Use Super 35 for film/video comparison.

You've said this multiple times, but I disagree.

If you are using cinema lenses perhaps, but most of us are using lenses designed for still photography. When shopping for a good vintage prime, a 50mm is considered a standard portrait lens. But throw that on a cropped sensor, and it is suddenly a much tighter FOV than advertised. You need lenses designed to go wider, and that is where the crop factor really becomes a force to be reckoned with.

I have a beautiful 50mm Nikkor that I used to take a shot of car on my Canon APS-C outside, with a slider all the way up against the house. I was able to get the entire car in the shot, with a bit of extra space on each side. When I switched to the GH2, same lens in the same position, I suddenly couldn't get the entire car in the shot anymore and had no more room to back up.
Apparently, the difference is more noticeable than I realized. And either way, this 50mm prime is NOT A STANDARD PORTRAIT LENS on any of these cameras. Except, of course, the 5D.

One of these days I'll post screenshots from that test so you can see how much of a difference the FOV makes between these two.
But yes, the GH2 has an odd shaped sensor that changes size with the aspect ratio. Shooting stills appears to be a painfully even smaller FOV than video (albeit taller, the sides get cut off). Thankfully, you can switch the photography mode to 16:9 and get the width back if you want. But you'll have odd shaped stills.

 

[cbrandin]

Actually, comparing a single dimension is the more valid way to calculate crop factor, you just have to pick the right one to compare. Decide on an aspect ratio, crop image area(s) to match that aspect ratio, and then take the ratio of the vertical, horizontal, or diagonal dimensions - all will yield the same answer. For example, if you crop 35MM FF (24mm x 36mm) to have a 16:9 aspect ratio you get an image size of 20.25mm x 36mm. Whether you compare the diagonals, the verticals, or the horizontals you get the same answer - a crop factor of 1.89. So the easiest way to do it is to compare whichever dimension - horizontal or vertical - which is not cropped to achieve a common aspect ratio (assuming you pick one or the other's native aspect ratio). If you are interested in 35mm FF aspect ratio (3:2) the crop factor becomes 2.24 because it is the vertical dimension which is not cropped (24/10.7). If you are interested in ND 16:9 aspect ratio the crop factor becomes 1.89 because it is the horizontal dimension which is not cropped (36/19).

If you are comparing with an academy 33mm motion picture frame, you get two different answers depending on which aspect ratio you choose. If you want the academy 35mm aspect ratio it is calculated by comparing vertical sizes (because the horizontal one has to be cropped on the GH2); the crop factor is 16/10.7 = 1.5. If you want the HD 16:9 aspect ratio the ratio is calculated by comparing horizontal sizes (because the vertical one has to be cropped on the academy 35mm camera); the crop factor is is 22/19 = 1.16.

Arguably, the worst way to calculate crop factor is to use the ratio of diagonals if the aspect ratios do not match.

Let's do the comparison everybody is actually interested in - that is, what is the GH2 crop factor compared to IMAX? If you crop the GH2 sensor to match the IMAX aspect ratio of 1:1.33783 (I'm assuming you are interested in including GH2 footage in your IMAX movie), the GH2 crop factor becomes 4.92!

 

[Apefos Adapter]

The dimension used to calculate a crop factor is ALWAYS the Diagonal because the diagonal defines the image circle and the angle of view and the focal distance of a lens relative to its sensor. So wneh comparing GH2 to a full frame STILL (not 5D for video) the crop factor will be 2x. the full frame STILL diagonal is 43,2mm and 43,2 / 21,6 = 2 So a 50mm still lens will be 100mm in GH2

 

[David W. Jones]

No a 50mm lens in a GH2 is still a 50mm lens.

 

[dishan]

No a 50mm lens in a GH2 is still a 50mm lens.

I'm sure there is some sort of point you are trying to make here, but I think I missed it.

My 50mm Nikkor on a GH2 has a vastly different FOV than it did on the camera it was originally designed and purchased for. Heck, on my old Canon it was roughly the equivalent of an 85mm- on the GH2 it is even deeper.

I know you've been around long enough to know that, so I'm assuming there is some sort of point you are trying to make here- maybe I'm just not seeing it?

Meanwhile, the point I think being made by others is that when comparing crop sizes on digital bodies, 35mm film has always been the standard by which they are judged. Because, when it all boils down, these are supposed to be replacements for STILL cameras. They happen to take excellent video, but anyone discussing adapters, lenses, crop factors, etc, will always be comparing to 35mm equivalents. Saying that we should be comparing to s35 cinema film is just going to create a lot of confusion.

Maybe YOU only use your camera for video... but search for discussion about crop sizes on the internet, you'll undoubtedly stumble into a photography forum discussing the FOV of a 50mm on a cropped sensor. And I can guarantee you they are not comparing it to cinema film sizes. So why are folks trying to complicate the matter by using a completely different reference set? We should all be using the same universal language and just get along!

 

[Apefos Adapter]

a 50mm lens will always be 50mm in all cameras, but what changes it the EQUIVALENT do 35mm STILL. In GH2 a 50mm lens is EQUIVALENT to a 100mm in full frame STILL

 

[David W. Jones]

Like I said, a 50mm lens is always a 50mm lens, it doesn't matter what camera you mount it to. It is always a 50mm lens! The field of view from said lens will be determined by the sensor size but the lens does not magically become a 100mm when mounted to a M4/3 camera.

 

[Kholi]

I've always been confused on FOV and AOV, but I think even the FOV of a 50mm is also still the same, but the AOV changes due to the sensor size?

I'm pleading ignorance on this one. Just can't remember.

 

[Apefos Adapter]

both FOV (field of view) and AOV (angle of view) changes relative to sensor size. The rule is: take the lens focal lenght and multiply it by the crop factor.

Example (for GH2 and 35mm STILL, crop factor 2)

lens focal lenght = 50mm
crop factor = 2
50 x 2 = 100mm (equivalent to 35mm still when used in GH2)

 

[GrahamH]

a 50mm lens will always be 50mm in all cameras, but what changes it the EQUIVALENT do 35mm STILL. In GH2 a 50mm lens is EQUIVALENT to a 100mm in full frame STILL

And just to be über-pedantic, we need to specify we talking about equivalent to the FOV of a 100mm. Some folk talk about "equivalents" in discussions of depth of field, which is different again.

 

[Mike@AF]

I'm sure there is some sort of point you are trying to make here, but I think I missed it.

My 50mm Nikkor on a GH2 has a vastly different FOV than it did on the camera it was originally designed and purchased for. Heck, on my old Canon it was roughly the equivalent of an 85mm- on the GH2 it is even deeper.

I know you've been around long enough to know that, so I'm assuming there is some sort of point you are trying to make here- maybe I'm just not seeing it?

Meanwhile, the point I think being made by others is that when comparing crop sizes on digital bodies, 35mm film has always been the standard by which they are judged. Because, when it all boils down, these are supposed to be replacements for STILL cameras. They happen to take excellent video, but anyone discussing adapters, lenses, crop factors, etc, will always be comparing to 35mm equivalents. Saying that we should be comparing to s35 cinema film is just going to create a lot of confusion.

Maybe YOU only use your camera for video... but search for discussion about crop sizes on the internet, you'll undoubtedly stumble into a photography forum discussing the FOV of a 50mm on a cropped sensor. And I can guarantee you they are not comparing it to cinema film sizes. So why are folks trying to complicate the matter by using a completely different reference set? We should all be using the same universal language and just get along!

Well, then I'd say you should go to the photography forums and discuss crop factor with full frame sensors there. The vast majority (meaning nearly all) discussion here is regarding shooting video, so therefore we should be talking about crop factor when shooting video and comparing to S35 not FF35.

I don't think anyone is disputing the 1.9x 2.0x or 2.1x (or whatever it is) crop factor when comparing to the 5D or any other full frame-sized sensor. But really that crop factor has no bearing when you shoot with video because full frame is not the standard for shooting movies, Super 35 is. I really don't understand why no one gets this.

And as far as the image circle of the lenses goes and a still lens having a different image circle than a cinema lens, yes that might be possible, but the image circle of lenses is vastly more difficult to find out than sensor or frame sizes. A lot, actually most, lens manufacturers don't publish the image circle size. However if you take a still lens and put it on a GH2 and a Scarlet, and then take a cinema lens and put it on a GH2 and Scarlet, both lenses will have the same crop factor when comparing the GH2 to the Scarlet. And plenty of people are using still lenses on larger sensor cameras than the GH2, and plenty (not as many as the other obviously though) of people are using cinema lenses on the GH2 and other DSLRs. So a still lens isn't just a still lens anymore. They are being used for shooting video and movies in great numbers now. So you really want to determine crop factors by comparing sensor size only, otherwise it gets tremendously more confusing for people than it clearly already is. Not every 50mm still lens has the exact same image circle, and not every 50mm cinema lens has the exact same image circle either.