GH2 crop factor 1.86x or 2x ?

yoclay said:
I cannot believe there is 7 pages of debate on the crop factor in this forum. What has become of DVX user? It is getting so that no one can even write a few simple sentences here without being challenged, virtually aggressed here. It is very tiring.

What's the big deal? Since most of the lenses people are shooting on DSLR's were originally designed for photography on a FF camera, it makes sense that people refer to a crop factor for those very same lenses based on that. Like it or not, "Full Frame" (FF) is the easiest standard for most folks to relate to because the world of moving images has changed. It has grown exponentially and is populated by another culture. That of still photography.

People's feathers are being ruffled because the frame of reference now comes from the photo world rather than the video one?

Gimme a break, don't we have better things to do than worry about this?
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This is a beautiful post.
 
When using the Canon FD AE1 Program Full Frame Still camera, In my experience shooting people i found some rules for using the lenses. To shoot a portrait or a face close up I need to be 1,5 meter or more far away from the person. because if I get closer the nose would increase in size. So the best lens for a portrait (from chest to head) is from 70mm to 100mm (in 35mm still) and this will be 35mm to 50mm in GH2. For a face close up the best lens is a 135mm in full frame still (about 70mm in GH2). To shoot a group of people i found the best wide angle is the 35mm because any wider than this have distortions, so I just used the 28mm when realy needed. 35mm in still will be close to a 17mm or 18mm in GH2. So following this rules and using a great flash (the 299T) I got great photos and everybody loved my job with the Canon Fd AE1 Program. Due to this background it is important to me to know the GH2 crop factor comparing to 35mm still to know the best lens for each situation.
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I think you're getting a feel for it now. Once you start thinking in terms of the system you are shooting on, it becomes a lot clearer and less confusing. : -)
 
I think I have only seen two 70mm (65mm) films [FONT=helvetica, arial] It's a Mad, Mad, Mad, Mad World[/FONT] and 2001. I knew those movies were related!
 
motionflow said:
Hi Barry,

The sensor in 4:3 mode is quoted as measuring 17.3mm horizontally, and yields an image 4608px wide in that mode. In 16:9 mode, we know it yields an image 4976px wide. Therefore, if I'm not mistaken, wouldn't the math needed to determine the horizontal measurement of the sensor in 16:9 mode be the following?

17.3mm / 4608 * 4976 = 18.68mm

Any thoughts on this? Is this too simplistic for some reason?
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Okay. I've answered my own question to my own satisfaction ;-) The above rationale seems correct but assumed a constant (one to one) pixel mapping relationship in each aspect ratio mode that needed to be proven. I.e., one needed to prove that neither aspect ratio mode scales up or down an image compared to the other as part of some internal post process on the camera.

To confirm this assumption, I just took two detailed photos on a locked off tripod - one in 4:3 mode (for which we know the sensor size) and one in 16:9 mode (for which we don't know the sensor size). Overlapping those two images in Photoshop, one can see that they line up perfectly in scale (in the sense that neither image is a scaled up or down compared to the other).

So, based on this fact, and based on the knowledge of pixel dimensions in both modes, it seems to me that the horizontal dimension of the GH2 sensor in 16:9 mode is indeed 18.68mm.

If anyone can find some mistake in my reasoning and experimentation, I'd love to be corrected in order to find the correct value.

Thanks
 
You don't buy a lens like that, you rent. I've worked with a PL mount converted copy several times, Otto Nemenz owns it.
 
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I am fully aware that posting in this thread is opening a can of very dead worms, as the whole crop discussion is somewhat irrelevant and more on the geek nerd side of things and has little to do with making a good video. However, I must ask this, please bare with me, because this is bugging me and I feel dumb for not being able to figure it out.

I will pose a situation and I just need an answer from anyone willing to participate in 2014. edition of crop thread. This is the situation;

GH2 in video mode, taking a regular 24p 16x9 video. Two lenses.

1. SLR Magic Noktor Hyperprime for mFT, 50mm
2. old Helios 88, 50mm

What would be the movie standard S35 equivalent for both of these lenses in this situation, GH2, video mode. Thanks :)
 
See that is exactly what bothers me, those 2 lenses are both marked 50mm but on a GH2 in video mode they will definitely and most certainly not produce the same FOV.

I made a quick test, video mode, 24p, from the exact same position (~3 feet from the monitor) and centered on your S35 :D


Helios 44, 52mm
sPgWu1U.jpg


Lumix 14-140, zoomed just notch over the 50mm mark, probably somewhere around 52-54 range
uBRctsM.jpg
 
Another test, this one is probably way more helpful than the previous one, and I hope I'm one step closer to epiphany hah

Evidently, 14-140's 70mm is identical to Helios 52mm. Also, I don't know why I've read somewhere that video and photo modes are different so different crop factors should be applied on GH2.

If you look here, I took videos at these focal lenghts and then photos in 16:9 ratio, same position same angle...exif told me correct focals, since the numbers on 14-140 are apparently not spot on.

JUuzj3u.jpg


Now I'll take a breather...not only do I don't know how to translate these lens numbers, now I don't even know where does x2 factor come from...apparently my old 35mm standard Helios lens is not acting like 104 mm.
 
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-Tom- said:
...not only do I don't know how to translate these lens numbers, now I don't even know where does x2 factor come from...apparently my old 35mm standard Helios lens is not acting like 104 mm.
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That's because the Helios is a 58mm lens, not 52.
 
Any crop when compared to a different camera comes from the sensor, and not the lens, hence any lens you placed in front of said sensor would have the same crop value.
 
I'm absolutely sure I've read somewhere on forums (don't know which video forums exactly, not necessarily DVXuser) that legacy lenses are not as useful on GH camera because the crop factor doubles their focal length.

From what I've tested out today, Helios 58 acts pretty similar to Lumix's focal lengths...

I guess this whole confusion stems from the whole crop sensor nomenclature....yes I know that 20mm lens is 20mm lens but the application changes everything. Lumix 20mm lens with specific Lumix mount made for Lumix cameras may be labeled 20mm, but I don't think that anyone in this 35mm photo film world will believe that is a 20mm lens. Because to them (and they make the standards) that's a 40mm lens.

If GH2 can write exact focal length in my exif file, they could've put a small addition to their display to inform/remind people where they actually are, like this

MWK368h.jpg


Question - do cine lenses use the photographic 35mm numbers to define focal length? Or do they have a more logical way :)
 
-Tom- said:
I'm absolutely sure I've read that legacy lenses are not as useful on GH camera because the crop factor doubles their focal length
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This is a reference to the Micro 4/3 format 2x crop factor when compared to the Full Frame 35mm Still Photo format.

So a 50mm lens on a Full Frame sensor camera has the same FOV ( Field of View ) as a 25mm lens on a Micro 4/3 sensor camera.

With the GH2 camera the crop factor is 1.86x, so you get a slightly wider FOV compared to a standard Micro 4/3 camera. ( like the GH3 or the Olympus EM-1 )


The Full Frame format is not a great reference for video cameras, as most video cameras do not use Full Frame sensors. The Super35 cine format would be a better choice.
 
To "see the crop" you would put the Helios (or the Lumix) on an S35 camera and take a picture, then put it on a GH2 and take a picture. The crop is due to the different sensors, not teh different lenses.

When the same lens is use on both cameras, the resultiing S35 picture will have a field of view that is wider by a factor of 1.86/1.5.

If you put both lenses on the same camera, any apparent crop can only be due to the focal length labeling being imprecise.

The Gh2 has a 1.86 factor only in 16:9 mode. In 4:3 or 3:2 mode for stills, it changes the way it uses the sensor and the factor becomes closer to 2.0.
 
Got it. But I have just one more question and I think I'll be 100% set on this whole conundrum. The millimeters.

Say you read a interview with some DOP and he says "one of my favorite lenses on my latest movie is Brand XYZ 40mm". Since he's obviously answering questions about his filmmaking, when he says "40mm" what is he referring to?

Photographic 35mm type of "40 mm view" or do cinema people have their own set of standards from Super35?


I guess my questions is: do all the lenses on the market, photo or video lenses, have their focal lengths marked according to photographic 35mm frame reference?
 
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