Micro 4/3 Crop Factors

The place for questions about shooting with Blackmagic Cameras.
  • Author
  • Message
Offline
User avatar

RealSting

  • Posts: 21
  • Joined: Sat May 12, 2018 9:16 am
  • Real Name: Jay Ryde

Micro 4/3 Crop Factors

PostThu May 17, 2018 1:45 pm

I'm not understanding why if you use a M4/3 sensor and a M4/3 lens crop factors are still a .. well, a factor! OR is this not the case? So, to be clear, If I use a 12mm - 40mm lens on the new BMPCC 4k, I will actually see 12-40mm in my viewfinder.
Offline

Denny Smith

  • Posts: 7966
  • Joined: Thu Aug 01, 2013 4:19 pm
  • Location: USA, Northern Calif.

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 3:57 pm

Yes, forget about crop factors, this was a marketing term used to get 135mm film photographers to use the new APS-C digital cameras, by comparing the angle of view between full frame 135mm and the smaller digital sensor, and only adds confusion if you were not a 135mm film photographer. It (crop fsctor) has nothing to do with actual focal length of a lens, which does Not change when you use a given focal length lens, like 12mm, on a MFT size sensor or a larger sensor camera.

So your 12-40mm lens on the new Pocket camera will have a slightly wider angle of view than it would on the smaller MFT sensor in the Panasonic GH4/5, which has a smaller sensor than the GH5S or new BM Pocket camera 4K.

A good starting point is to know what focal,length is a “normal” AOV (45-degree) lens, and on the MFT format this is 25-30mm, based on the diagonal of the sensor area in native 4:3 format. The diagonal does not change on the new Pocket 4K, and remains the same at 16:9 or 17:9 aspect ratios (unlike the GH4/5 which gets a smaller shooting area in 16:9). So from 25mm, going to 12 or 15mm is a wide angle and going to 35-40 and up is a long or tele lens focal length.

I find the 12-40 a nice focal length range for the MFT format, giving a nice wide to reasonable long shot.
The Oly 12-40 f/2.8 Pro Zoom is a very nice lens. Also the Panasonic Leica 12-60 makes a good video Zoom, as it is parfocal, has steppless iris control, and very quick and quiet zoom/iris motors. It’s only drawback is it changes thr max f/stop from f/2.8 to f/4 as you zoom out to the 60mm end (known as reaping): But if you are shooting at f/4 to 5.6 this is not an issue. Still cameras use auto shutter or ISO to compensate the ramping, the BM Micro and new Pocket Camera 4K can set auto shutter angle to compensate the f/stop change.
Hope this helps.
Cheers
Denny Smith
SHA Productions
Offline

michaeldhead

  • Posts: 38
  • Joined: Sat Mar 25, 2017 5:41 pm

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 5:06 pm

Crop Factor compares the field of view of the sensor size to the field of view of a lens on a 35mm film camera (or full frame sensor in digital).

There are a lot of small variations, but overall the basic is this: the MFT sensor has a x2 crop factor in terms of field of view, so a 12mm lens on MFT has the same field of view as a 24mm lens on full frame (12x2). To get an equivalent of a 50mm field of view (a "normal" lens) on full frame, you'd need a 24mm MFT lens (actually for a 48mm equivalent field of view).
Offline

John Paines

  • Posts: 1299
  • Joined: Tue Jul 28, 2015 4:04 pm

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 7:28 pm

michaeldhead wrote:Crop Factor compares the field of view of the sensor size to the field of view of a lens on a 35mm film camera (or full frame sensor in digital).


It would be more accurate to say this is how persons coming from still photography like to characterize cinema/video size sensors. But it's of no practical or instructional value to persons who aren't coming from still photography -- those folks might do better to think of a cinema reference, if they must have a reference.

If you really wanna talk crop factors, the m43 sensor is nearly the same size on the horizontal as a traditional 1:1.85 motion picture film frame. So, except for the mathematically unforgiving (it's 17-18mm v 21mm), there's no significant crop-factor between m43 and traditional cinema. And no crop factor to dream or worry about. Just put the lens on and see what you've got.
Offline

michaeldhead

  • Posts: 38
  • Joined: Sat Mar 25, 2017 5:41 pm

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 8:54 pm

John Paines wrote:Just put the lens on and see what you've got.


Or you could use the convention that has existed for twenty-two years since 1996 and Canon's APS launch, which is understanding how crop factors affect equivalent field of view with different lenses.
Last edited by michaeldhead on Thu May 17, 2018 9:01 pm, edited 1 time in total.
Offline

michaeldhead

  • Posts: 38
  • Joined: Sat Mar 25, 2017 5:41 pm

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 9:00 pm

My favorite full-frame field of view is from a 35mm lens. But I just ordered a Pocket 4k camera, and I'm excited about it.

So if I get an basic EF-MFT adapter and slap on my 35mm view, I better have an understanding that my 35mm lens will have a field of view of a 70mm lens; which is to say my wide lens will suddenly behave like a telephoto lens.

Even with a Speedbooster Ultra, it will be close to a field of view of 60mm (I think - I don't have the exact numbers in front of me).

But if I want the same field of view as my 35mm lens has on a full frame camera, I will need a MFT lens that is half as long - so I'll need to look for a 16mm MFT lens to get close to the same field of view.

It's much better to understand how field of view affects what you see rather than just "slap a lens on it and see what you get".
Offline

John Paines

  • Posts: 1299
  • Joined: Tue Jul 28, 2015 4:04 pm

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 9:09 pm

michaeldhead wrote:Or you could use the convention that has existed for twenty-two years since 1996 and Canon's APS launch, which is understanding how crop factors affect equivalent field of view with different lenses.


It's a convention among still photographers who shoot video --and a passionately held one, judging from the sensitivities on this subject, on both sides of the argument.

But it's not a convention among cinematographers, and it's hard to see what the OP, who gives no indication he has FF FOV focal lengths in his head, would gain from such a reference.
Offline

michaeldhead

  • Posts: 38
  • Joined: Sat Mar 25, 2017 5:41 pm

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 9:18 pm

John Paines wrote:It's a convention among still photographers who shoot video --and a passionately held one, judging from the sensitivities on this subject, on both sides of the argument.

But it's not a convention among cinematographers, and it's hard to see what the OP, who gives no indication he has FF FOV focal lengths in his head, would gain from such a reference.


I'm a cinematographer who happens to also shoot stills, but I learned videography first - and I still learned to take crop factor into account when making lens choices.

But it gets back to exactly what I was talking about before - knowing what lens behaves as ultra-wide, wide, normal, telephoto on different sensor sizes.

If you're expecting your 35mm lens to be wide on a MFT sensor, you're going to be in for disappointment when it suddenly behaves like a short telephoto instead of a wide angle lens.

There's a reason that even sales places like B&H list the 35mm equivalent for MFT lenses - https://www.bhphotovideo.com/c/product/ ... al_ed.html
Offline

John Paines

  • Posts: 1299
  • Joined: Tue Jul 28, 2015 4:04 pm

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 9:26 pm

Yes, and that B&H link is to still photography lenses, where the reference to FF makes more sense. But I can see we won't get far on this one, any more than all the others who argue about this world shattering difference.
Offline

michaeldhead

  • Posts: 38
  • Joined: Sat Mar 25, 2017 5:41 pm

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 9:31 pm

John Paines wrote:Yes, and that B&H link is to still photography lenses, where the reference to FF makes more sense. But I can see we won't get far on this one, any more than all the others who argue about this world shattering difference.


A lens that is often recommended for people that shoot video on cameras with MFT lens mounts - like the Pocket 4k.

How would you explain field of view and crop factor to someone who is just learning?
Offline

michaeldhead

  • Posts: 38
  • Joined: Sat Mar 25, 2017 5:41 pm

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 9:32 pm

Besides "just put a lens on it and see what you've got", since most people can't buy a huge lens kit to start.
Offline

Denny Smith

  • Posts: 7966
  • Joined: Thu Aug 01, 2013 4:19 pm
  • Location: USA, Northern Calif.

Re: Micro 4/3 Crop Factors

PostThu May 17, 2018 10:36 pm

Simple, you start with the lens that is “normal” and go from there. You learn what the field of view is for the various lenses available for that format. Si a MFT size sensor would start with 25mm (same as Std 35mm Cine format), then 15-18mm is a WA and 35-50a tele. On a S16 BM Camera like the original Pocket/Micro Cameras, Norma FOV is attained with a 17.5mm kens, so 16-18mm will fit the bill, then 8-12mm a Wide Angle and 29/30mm yiur classic head and shoulders portrait focal length.

As previously mentioned, using a 135mm reference and crop factors only works if you are coming from a DSLR Camera. Even then, I shot both still and motion picture for 20 years, using cameras from 8x10 to S16, and never used “crop factor”reference to thr 135mm SLR, which was I main camera. I knew from experience which lens I needed for the format I was shooting to cover the subject at hand.
Cheers
Denny Smith
SHA Productions
Offline

michaeldhead

  • Posts: 38
  • Joined: Sat Mar 25, 2017 5:41 pm

Re: Micro 4/3 Crop Factors

PostFri May 18, 2018 5:01 pm

Denny Smith wrote:Simple, you start with the lens that is “normal” and go from there.


And if you don't know what a "normal" lens is to start?
Offline

Denny Smith

  • Posts: 7966
  • Joined: Thu Aug 01, 2013 4:19 pm
  • Location: USA, Northern Calif.

Re: Micro 4/3 Crop Factors

PostFri May 18, 2018 5:43 pm

That info is readily available here and on other web sites, like AbelCine, etc. just Google “normal focal length lens for (enter the format desired). :roll:
I just gave it for MFT and S16, the formats we are discussing. ;)
Cheers
Denny Smith
SHA Productions
Offline

Steve Holmlund

  • Posts: 297
  • Joined: Fri Jun 28, 2013 11:30 pm
  • Location: Montara, California

Re: Micro 4/3 Crop Factors

PostFri May 18, 2018 6:01 pm

The pCAM iPhone app includes a Field of View utility along with many other useful tools. You can specify your camera format, distance and focal length and it will give you the horizontal and vertical angles of view.

I find it quite helpful for doing comparisons if I don't have the particular camera and/or lenses.
Steve Holmlund
Hobbyist
BMPCC, vintage Rokkor lenses, Olympus 12-40, Panasonic 100-300 II
i7 8700k / GTX 1080
Offline

Denny Smith

  • Posts: 7966
  • Joined: Thu Aug 01, 2013 4:19 pm
  • Location: USA, Northern Calif.

Re: Micro 4/3 Crop Factors

PostFri May 18, 2018 6:13 pm

Thanks a Steve, excellent additional tool. I use pCAM when I need to match two cameras with different size sensors. Also Viewfinder Mk3 Apple IS application I run on my IPhone to see the AOV of a given lens on a given camera, works like a digital version of the old directors Viewfinder.
Cheers
Denny Smith
SHA Productions
Offline

Steve Holmlund

  • Posts: 297
  • Joined: Fri Jun 28, 2013 11:30 pm
  • Location: Montara, California

Re: Micro 4/3 Crop Factors

PostFri May 18, 2018 6:17 pm

Denny Smith wrote:Thanks a Steve, excellent additional tool. I use pCAM when I need to match two cameras with different size sensors. Also Viewfinder Mk3 Apple IS application I run on my IPhone to see the AOV of a given lens on a given camera, works like a digital version of the old directors Viewfinder.
Cheers


Just discovered that you can "pinch and zoom" in pCAM's preview! That makes it really easy to compare focal lengths.

I'm slow sometimes...
Steve Holmlund
Hobbyist
BMPCC, vintage Rokkor lenses, Olympus 12-40, Panasonic 100-300 II
i7 8700k / GTX 1080
Offline

Denny Smith

  • Posts: 7966
  • Joined: Thu Aug 01, 2013 4:19 pm
  • Location: USA, Northern Calif.

Re: Micro 4/3 Crop Factors

PostFri May 18, 2018 6:34 pm

Yes, a very nice feature added in one of the recent updates.
Cheers
Denny Smith
SHA Productions
Offline

Howard Roll

  • Posts: 279
  • Joined: Fri Jun 03, 2016 7:50 am

Re: Micro 4/3 Crop Factors

PostSat May 19, 2018 3:44 pm

I don't get why people get assed up about crop factor. It's another way of expressing information. How many users on this site work(ed) with film professionally, I'm guessing it's a low percentage.

Crop factor actually contains more information that just FOV comparisons. The crop factor also correlates to a difference in stop, for example;

1X FF 50mm @ T4
2X S35 32mm @ T2.8
3X S16 16mm @ T1.4

Same dof for all 3 systems.

For a given composition S16 will have 3 stops more DOF than 135, and 2 stops more than S35.....and that's one to grow on.

Now on to the real issue, why is US power referred to as 110v when it's clearly 120 volts.
Offline

Denny Smith

  • Posts: 7966
  • Joined: Thu Aug 01, 2013 4:19 pm
  • Location: USA, Northern Calif.

Re: Micro 4/3 Crop Factors

PostSat May 19, 2018 7:06 pm

Good point Howard, and 220 is actually closer to 240 vac. I guess back in the first part of the 20th Century, I spy was actual 220vac, split into two 110vac legs.
Cheers
Denny Smith
SHA Productions
Offline

Uli Plank

  • Posts: 2390
  • Joined: Fri Feb 08, 2013 2:48 am

Re: Micro 4/3 Crop Factors

PostSun May 20, 2018 12:38 am

Well, for noobs this may be further confusion.

While you are right about DoF, the exposure doesn't change: nonbody needs to close down a S-16 lens further than one for the 135 format (photographic FF) to get the same exposure under the same light. OTOH, one can easily build lenses with a smaller image circle for higher opening ratios, so 'speed' is normally better.

The only thing that really helps is wrapping your head around the whole subject instead of staring at numbers.
Offline

Jim Giberti

  • Posts: 63
  • Joined: Tue Mar 03, 2015 2:03 am

Re: Micro 4/3 Crop Factors

PostSun May 20, 2018 5:41 pm

Uli Plank wrote:The only thing that really helps is wrapping your head around the whole subject instead of staring at numbers.



Which in the end is all about shooting and gathering experience. And because pepople are people they will come to these things in the way that people do - from different perspectives.

And I hope that opinion is acceptable here.
Offline

Uli Plank

  • Posts: 2390
  • Joined: Fri Feb 08, 2013 2:48 am

Re: Micro 4/3 Crop Factors

PostSun May 20, 2018 9:34 pm

To learn a craft there is no better approach than experience. If you do not see and feel the artistic differences of different lenses, you should choose another craft anyway. And if you don’t own some lenses, rent or borrow to play with them.
Some of the greatest of all times used a very limited set of lenses, like Orson Welles or Akira Kurosawa. Other experimented with many, like Stanley Kubrick.

Return to Cinematography

Who is online

Users browsing this forum: Bing [Bot], Rakesh Malik and 6 guests