GH4 gh4 wide angle focal lengths

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dilby

Member
Hi all -

A while ago now I switched from my trusty Canon 600d running magic lantern to a GH4. It's been going fine as I do an odd job here and there, but now a real estate agent who had me do some videography of interiors has asked me to do some more. The issue is that I'm having what seems to be a common issue; getting wide with the GH4, and am reading info online that is confusing me further!

With the 600d (t3i), I was using a sigma 10-20mm lens which although a bit slow if Im being picky, was the perfect focal length. I liked that range of control (in a tight space I find that zoom is pretty much essential compared to a prime) but I'm confused how I can recreate it. From what I understand if I put that same lens on my camera now it would become the equivalent of 20-30mm (or thereabouts), but with a speed booster (which I own) it would remain 10-20. Is that correct so far?

I own the 12-35 f2.8 panasonic lens; so is that within the range of what the 10-20 used to be, or is it effectively 24-70? I'm confused if a lens is made for MFT if it takes into account crop factor or not in the naming.

For example, would this lens be the same focal length as the 10-20 sigma zoomed all the way out using the metabones or is it going to be effectively a 20mm?

If anyone has some suggestions on lenses too that would be great; the 7-14 panasonic seems to pop up quite a bit, but it's frustrating how expensive it is to get wide on the gh4 compared to be 600d! I can really only afford to buy a lens like that if I sell my speed booster, so another option would be to keep speed booster and buy a cheaper EF alternative if anyone knows of a good recommendation?

Sorry for all the questions and thanks!
 
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Have you tried using your Sigma 10-20mm zoom with your SpeedBooster adapter ?
( in theory this should give you the range you are looking for )

Otherwise, if you can live without the zoom feature there is a new lens coming out soon for Micro 4/3 cameras that might suit your needs...

Venus Optics Laowa 7.5mm f/2.0 : $499
 
No, the MFT lenses don't take the crop factor into consideration. So the 12-35 is a 24-70. Also, when shooting in 4k, there is an additional crop, so it's around 2.4x cropped. 1080p uses the full sensor, so the crop is 2x. Getting a speedbooster will bring you pretty close to an APS-C crop...If you want to cheap out, you can get a screw on wide angle adapter. Most pros wouldn't be caught dead using one, but I've found the wide adapters are pretty decent optically and don't induce any aberrations. I've used a .45x adapter from Neewer in a pinch and the footage was certainly usable. It's the telephoto adapters that are generally terrible and to be avoided.
 
The 600D is an APS-C camera. Don't worry about all the crop information and all that other garbage you will read online. The SpeedBooster can be factored in both directions. Instead of thinking about what it does to the lens think about what it does to the sensor. The Speedbooster makes the m43 sensor APS-C size so that same 10-20 mm lens will now look exactly the same as it does on your 600D camera. Since the SpeedBooster magnifies there are always two sides to the magnification lens. Instead of the complicated math dealing with what it does to the lens I find it easier to think of it as to how it can affect the sensor.

By increasing the sensor to a larger size you have the same FOV, DOF and in some cases sensitivity as that of the 600D camera. Thinking of the effect on the lens is a lot more confusing.
 
Thanks all - I should have made clear that I sold the 10-20 lens with the canon. What I don't really understand is that if its double, doesn't that mean to achieve the same as 10mm with an mft lens I'd need a 5mm? (Which obviously would be some sort of novelty crazy fish eye lens). I can understand the sensor is being increased - so that does that mean I'd be better off using a 20mm ef lens with the speedbooster than I would with a 10mm mft lens? Both would be resulting in an effective 20mm but the increased sensor size provided by the metabones would add a bit more size to the image. Is that right?
 
Also, Ive read the metabones makes it full frame size like the 5d. But is that wrong, and it's just making it asp-c size like my 600d?
 
Canon 5D Full Frame camera : Crop factor = 1.0x 50mm lens = standard lens

Canon 600D APS-C camera : Crop factor = 1.6x 31 mm lens = standard lens

Panasonic GH4 camera : Crop factor = 2.0x 25mm lens = standard lens


Sigma 10-20mm lens x 600D Crop factor 1.6x = 16-32mm lens on a Full Frame camera like the Canon 5D

Sigma 10-20mm lens x GH4 Crop factor 2.0x = 20-40mm lens on a Full Frame camera like the Canon 5D


Rule of thumb to convert a Full Frame lens to it's Micro 4/3 equivalent : Divide Full Frame focal lens by 2 ( so a 50mm lens becomes a 25mm lens )

...And to complicate things a bit more the GH4 crop factor becomes 2.3x when you are shooting 4K video ( 4K video does not use the full GH4 camera sensor )
 
The actual crop factors of the GH4 are 2.08x in 1080 and 2.49x in 4k video recording.

You really need a 7.5 or 8mm lens in 4K on the GH4 to get full interiors. I have used a 7.5mm fisheye and defished in post to make it look closer to rectilinear. It doesn't work quite right though.

If you are really going to be doing real estate work, you will want one of these -

https://petapixel.com/2017/04/28/venus-optics-new-laowa-7-5mm-f2-worlds-widest-f2-lens-mft/

The video samples and images from it are spectacular and you won't have to lug around all these huge lenses to run on a speedbooster. I think this is going to be my next purchase.

In any case another option to look into.

Cheers,
Pete
 
Again just think of how that magnification works on the sensor.

Canon 600D has a sensor that is 22.3mm wide. GH4 has a sensor that is 14.38mm wide when factoring in the extra crop of UHD video. Shooting UHD (4k) on the GH4 doesn't use the full sensor. If the Speedbooster shrinks lenses by .71 then you can use that same amount to divide by for the sensor. 14.38 / 0.71 = 20.25mm. Not the exact width of the 600D but much closer. The SpeedBooster XL has a little extra magnification so 14.38 / 0.64 = 22.46mm or almost identical to the FOV and DOF of the Canon 600D.

So if you really liked 10mm on the 600D and you do have a SpeedBooster then get the same type of lens and 10mm will look the same to you.

The entire crop factor thing has been made 100x more complex then it needs to be. It is really just about sensor width and that is all that really affects the results we get from lenses when dealing with video. The FOV is a match because the magnification enlarges the sensor by the same amount it shrinks the lens on the other end. The DOF is equal because again the sensor is now larger and grabbing the same amount of image from the lens. The SpeedBooster is known to affect one stop of light but that 1 stop also applies to DOF calculations because the sensor is magnified 1 stop larger by the lens in the SpeedBooster.
 
I'm not sure how well the optics are but you could check out the Toking 11-16mm f2.8. 11mm isn't far from the 10mm you used to get but the lens is faster and a constant f2.8 across the zoom range. You do lose 4mm on the long end however. Seems to be around $499.00.
 
Thanks all. I'm sure that Leica 8-18 is a beauty, but it's just unaffordable for me at this stage. The Venus Optics lens looks a possibility, although I really do like having a bit of a zoom range when in a tight space. Reason is I always want to show only the width that I HAVE to, and not to overdo it when unnecessary. So if I'm pressed up against a washing machine in a laundry room I might go all the way out, but if I'm in a living room I might be able to afford going 20mm and not 10mm etc. There may be some different opinions on here about that, but that's just my thoughts.

Another question that I have after reading all this; is using the sigma 10-20mm lens on the GH4 with the speedbooster going to be better in low light than on the canon 650d because it will be comparatively a stop faster?
 
dilby said:
Thanks all. I'm sure that Leica 8-18 is a beauty, but it's just unaffordable for me at this stage. The Venus Optics lens looks a possibility, although I really do like having a bit of a zoom range when in a tight space. Reason is I always want to show only the width that I HAVE to, and not to overdo it when unnecessary. So if I'm pressed up against a washing machine in a laundry room I might go all the way out, but if I'm in a living room I might be able to afford going 20mm and not 10mm etc. There may be some different opinions on here about that, but that's just my thoughts.

Another question that I have after reading all this; is using the sigma 10-20mm lens on the GH4 with the speedbooster going to be better in low light than on the canon 650d because it will be comparatively a stop faster?
Click to expand...

Not really. The SpeedBooster increases a stop but the smaller m43 loses a stop so it more or less cancels out. The speedBooster gets you to roughly the same low light performance as the 600d.

I say roughly because sensitivity isn't that easy and there are a lot of factors that go into how much light a sensor can take in like the quality of noise reduction and so forth. It should be roughly the same which is why I suggested the Tokina 11-16mm f2.8 lens. Gives you a bit more light on the wide end and a lot more on the far end.

The downside to the Panasonic 8-18mm at f2.8 is you can't use the SpeedBooster with it so compared to the Tokina/SpeedBooster it will be a stop darker. Using the 8-18 Panasonic lens will actually be less sensitive compared to what you used in the past.
 
Thomas Smet said:
I'm not sure how well the optics are but you could check out the Toking 11-16mm f2.8. 11mm isn't far from the 10mm you used to get but the lens is faster and a constant f2.8 across the zoom range. You do lose 4mm on the long end however. Seems to be around $499.00.
Click to expand...
The Tokina is a bit soft and has quite some chromatic abberation but it is still a nice lens and can get you very wide with f/2.0 using a speedbooster. Infinity focus can be a problem and you may have to adjust your speedbooster slightly.

Here are some test shots done with this lens:
 
The OP doesn't list where they live, but in the USA hiring the 8-18mm from LensRentals is very affordable (see link above).
 
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