GH4 Moving from larger sesnor format to an m4/3 environment...considerations?

T

True North

Well-known member
Thinking of buying into the world of M4/3 with the new GH4. I like the idea of having a hybrid camera for both video and photos in such a compact form factor.

I think there are enough good lens options to over come the challenges of getting good wide shots with a 2x crop factor

The one issue I have problems getting over are problems of light. In equivalency terms and as I understand it, I would be doubling the f/stop of a native m4/3 lens. For example of a m4/3 f/2.8 lens would be the equivalent of a f/5.6 lens on a Full Frame camera.

My question is to those who have moved from a large sensor camera or to those who currently move between larger sensor and m4/3 sensors on a regular basis. Have you had any issues or difficulties with getting enough light with your m4/3 rig ? Any other issues I should consider ?

Not trying to cause a war here, just looking to hear about peoples experiences, cheers!
 
True North said:
Thinking of buying into the world of M4/3 with the new GH4. I like the idea of having a hybrid camera for both video and photos in such a compact form factor.

I think there are enough good lens options to over come the challenges of getting good wide shots with a 2x crop factor

The one issue I have problems getting over are problems of light. In equivalency terms and as I understand it, I would be doubling the f/stop of a native m4/3 lens. For example of a m4/3 f/2.8 lens would be the equivalent of a f/5.6 lens on a Full Frame camera.

My question is to those who have moved from a large sensor camera or to those who currently move between larger sensor and m4/3 sensors on a regular basis. Have you had any issues or difficulties with getting enough light with your m4/3 rig ? Any other issues I should consider ?

Not trying to cause a war here, just looking to hear about peoples experiences, cheers!
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I would suggest not getting in to the 'crop factor' type thinking, but think in terms of the new to you 4/3 configuration.

There is no need for 'equivalent' in terms of f-stop and 'light'. F-stop is an f-stop... and on most 35mm lenses that have not be specifically calibrated... the indicated 'f-stop' is really more of a 'guide'... but that's a different story.

What does change, is the angle of view for a given lens, (or Field of View...), and Depth of Field calculations.

There are some online widgets that allows one to calculate AoV/FoV for given lenses and sensors sizes, and with an estimate of the Circle of Confusion (CoC) you can get an idea of the Depth of Field that the lens+sensor+f-stop will yield.

I've bought and used two iPhone apps:

pCam App

Toland App

Since I don't have stock in either, but find features of both helpful, I'm recommending that these be used to answer all questions relating to lens setup for the supported set of cameras.
 
True North said:
The one issue I have problems getting over are problems of light. In equivalency terms and as I understand it, I would be doubling the f/stop of a native m4/3 lens. For example of a m4/3 f/2.8 lens would be the equivalent of a f/5.6 lens on a Full Frame camera.
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The amount of light is exactly the same with m4/3 vs a larger sensor. A Nikon 50mm f/2.8 lens on a GH4 will be just as bright as that same lens on a Nikon D800. The difference is that the GH4 will make the image look more "zoomed in" because of the size of the sensor. But it will be the exact same brightness.
 
j1clark@ucsd.edu said:
I would suggest not getting in to the 'crop factor' type thinking, but think in terms of the new to you 4/3 configuration.
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I agree - once I got a handle on the m4/3 lens options out there, I stopped worrying about crop factor, it's a non-issue to me

j1clark@ucsd.edu said:
There is no need for 'equivalent' in terms of f-stop and 'light'. F-stop is an f-stop... and on most 35mm lenses that have not be specifically calibrated... the indicated 'f-stop' is really more of a 'guide'... but that's a different story.
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This is not my understanding based on what I have read.

Here is a great paper on Equivalence, which will be infinitely more eloquent than I ever will at explaining what I mean

http://www.josephjamesphotography.com/equivalence/

My understanding is that a Full frame sensor with a FF 50mm lens set to f/5.6 will be the equivalent of M4/3 25mm lens set to f/2.8 on a M4/3 Camera. Like I said I am not worried necessarily about the FOV or the DOF.

I am curious about the limitations of using an m4/3 camer in low light situations. It is my understanding that all things being equal, an M4/3 25mm lens set to f/2.8 on a m4/3 camera will typically look about half as 'bright' as a FF 50mm lens set to f/2.8 on a FF sensor. If you understanding or ecperience is different I would love to hear about it.


j1clark@ucsd.edu said:
What does change, is the angle of view for a given lens, (or Field of View...), and Depth of Field calculations.

There are some online widgets that allows one to calculate AoV/FoV for given lenses and sensors sizes, and with an estimate of the Circle of Confusion (CoC) you can get an idea of the Depth of Field that the lens+sensor+f-stop will yield.

I've bought and used two iPhone apps:

pCam App

Toland App

Since I don't have stock in either, but find features of both helpful, I'm recommending that these be used to answer all questions relating to lens setup for the supported set of cameras.
Click to expand...

I also understand the field of view and the depth of field changes, but I wasn't aware of the specific calculations, so thanks for the online widget suggestions
 
Jaime Valles said:
The amount of light is exactly the same with m4/3 vs a larger sensor. A Nikon 50mm f/2.8 lens on a GH4 will be just as bright as that same lens on a Nikon D800. The difference is that the GH4 will make the image look more "zoomed in" because of the size of the sensor. But it will be the exact same brightness.
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The zoomed in look or FOV or Crop Factor...I get that part and I am fine with that. I understand it (I think) and I have rationalized that reality so that it isn't a concern of mine.

The light portion or 'brightness' is the only area where I have questions which I have outlined in my response above
 
Brightness does not change... F2.8 on full frame at ~ISO400 will expose the same as m43 at f2.8 ISO400.

What does change are the field of view and depth of field, which effectively double from ff to m43 - so the example 50/f2.8 lens on m43 would have similar fov and dof as a 100/f5.6 on full frame, but would exhibit the same exposure characteristics on both.
 
mcbob said:
Brightness does not change... F2.8 on full frame at ~ISO400 will expose the same as m43 at f2.8 ISO400.

What does change are the field of view and depth of field, which effectively double from ff to m43 - so the example 50/f2.8 lens on m43 would have similar fov and dof as a 100/f5.6 on full frame, but would exhibit the same exposure characteristics on both.
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ok, I think I get it now. So getting a shallow depth of field look, so easy to get out of a full frame sensor when using a wide open fast lens is more difficult on a M4/3 setup. So in your example the DOF in the 50mm M4/3 at F/2.8 would be about the same as the DOF you can pull out of 100mm Full Frame lens and sensor at f/5.6...correct?

Thanks
 
You can get a speedbooster if you're worried about FOV on m4/3. I've gotten one. I'm not nutz about putting a piece of glass like that between the sensor and my lenses so I'm going for an s35 sensor next but really, it looks pretty good so far.
 
Don't compare with a full frame sensor, it's not the norm and is rarely used in cinema. If anything, use a s35mm size to compare, it's what we see 90% of the time when watching films. Also your making more out of it then necessary. M4/3rds sensor is close to s35, granted it's smaller, but the field of view isn't anywhere near as different as with a full frame. Another misconception people make is when they compare say 50mm on a full frame with 50mm on a m4/3rds sensor. 50MM IS 50MM is 50MM, no matter what camera it's on, the only thing that changes as touched on by Jaime is field of view, dof. That's it, nothing more or less. I think people forget that the 50mm measurement is from sensor to lens.
 
I agree, I don't like the speedbooster much, however it can save you in certain conditions. But I would never rely on it for much more. I just don't like the tradeoff, especially when it comes to bokah!!
 
There are a couple of huge advantages to going the m43 route.

Firstly is the ETC function. There simply isn't anything that can compete for long range work at any price. I do lots of wildlife filming with a 600mm Nikkor AIS and it gives an equivalent focal length of 3000mm at f/5.6. There's no such lens ever made that can compete at any price on any camera with this function.

Secondly, you can use very fast lenses wide open without having such a fine depth of field that you can't keep anything in focus. A 25mm at f/1.4 has the same depth of field and field of view as a 50mm at f/2.8 on a full frame, yet it is allowing over three times as much light in. This more than makes up for the lower light sensitivity of the GH sensors vs. the higher end full frame dslrs. m43 systems crush the APS-C cams for light gathering at their usable ISO limit of about 1600 with these faster lenses for a similar DOF and FOV. I can't tell you how valuable this is in keeping focus when scenes are dimly lit. I found full frame cams to be nearly worthless for filming any sort of moving action anywhere even close to wide open. You just can't keep anything in focus with that system unless you have ample light and stop down, defeating the whole purpose and cost of such.

I've found a 17mm f/1.8 to be the sweet spot for the m43 system on a stabilizer. You can follow a subject in relatively lower light at f/1.8, yet still keep a semblance of a usable "in focus" depth of field. It simply doesn't work anywhere near as well with full frame and definitely not with APS-C sized sensors.

Cheers,
Pete
 
True North said:
I am curious about the limitations of using an m4/3 camer in low light situations. It is my understanding that all things being equal, an M4/3 25mm lens set to f/2.8 on a m4/3 camera will typically look about half as 'bright' as a FF 50mm lens set to f/2.8 on a FF sensor. If you understanding or ecperience is different I would love to hear about it.
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I find no real limitations in low light situations. The m4/3 system has several examples of "fast glass" that coupled with good high ISO performance have made low light situations a breeze for me. I deal with things in a very practical sense, I don't give a "hoot" for tables, calculations, formulae or anything like that.

Photography (and motion picture work) is a visual medium, our cameras now let us "prevue" what we're about to get. I have the Lumix 20mm f1.7, Pan/Leica 25mm f1.4, Oly M.Zuiko 45mm f1.8, and the Oly M.Zuiko 75mm f1.8...All tremendous low light lenses that are great performers.

I wouldn't worry about low light work with any of the current m4/3 cameras with any of the above listed lenses. And the weight saving advantage is nothing short of amazing.
 
I have a EF speedbooster on my FS700 and IMO it works great, I have been very happy with that purchase so far. However, part of what I really like about the whole M4/3 world are the compact lens sizes. I will probably be getting a set of Rokinon Primes soon which I will get in a Nikon mount for which I will probably buy a new speedbooster for both my FS700 and eventually the GH4.

I want to know where I am at relative to full frame. I am not comparing as in comparing to determine which one is 'better'. I am comparing because with my FS700+Speedbooster I am shooting pretty much in full frame right now. I just want to understand the difference to understand what to expect. I am not comparing to decide whether or not to get a GH4 OR a Full Frame option. Like I said earlier I like the concept of having a hybrid camera option in a relatively small form factor like M4/3
 
True North said:
I want to know where I am at relative to full frame.

Like I said earlier I like the concept of having a hybrid camera option in a relatively small form factor like M4/3
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Get one, maybe a GH3 (used going for $800 to $850) to try it out and see if you want to go for a GH4 later. I think you're "over analyzing" it all getting bogged down with details that may be more irrelevant than not.

Visually, pretty much anything you can do with FF (except drastic cropping) you can do with m4/3.

In still work I'm achieving essentially the same looks I used to get with Hasselblads and Mamiya RB67, 2 1/4 x 2 1/4" and 2 1/4 x 2 3/4" negs.
 
c3hammer said:
There are a couple of huge advantages to going the m43 route.


I've found a 17mm f/1.8 to be the sweet spot for the m43 system on a stabilizer. You can follow a subject in relatively lower light at f/1.8, yet still keep a semblance of a usable "in focus" depth of field. It simply doesn't work anywhere near as well with full frame and definitely not with APS-C sized sensors.

Cheers,
Pete
Click to expand...


I agree that 1.4-1.7 in low light situations provides a 'sweet spot' for focused DOF. I shoot a lot of weddings and always use primes open at 1.7 or greater for receptions. With a single led light and such a lens, I can keep ISO below 2000, which is my personal cutoff for wedding work.

I admit that this full frame 'equivalent' comparison has confused me as well. I get the crop factor and DOF equivalents, but the fstop is tricky when practically applied. Partially because I see still images from photographers shooting the same shot as me with basically the same lens and their images look a lot brighter (when removing the flash equation). For example, I was shooting a 'first look' using my 12-35 2.8 amd working with a photographer using a 24-70 2.8 on a full frame Nikon. Nothing other than ambient light, but his image was so much brighter. I guess because full frame can boost ISO higher without as much noticeable grain? I was well below ISO 1000 however as this was around sunset with plenty of ample light.
 
The full frame cams from Nikon and Canon will shoot pretty clean images at ISO 6400. The 1DX and 1DC will shoot clean up to ISO 12,800. The practical limit on the GH2 or G6 is ISO 1600, maybe 3200 on the GH3.
 
I would imagine that there are some more efficiencies with the GH4 sensor. Panny reps have already said there is improved DR etc...

Might have better and cleaner ISO gain abilities. I guess we will have to wait and see
 
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