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Andrew Reid

Fast apertures on the GH5 = Full frame

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@horshack If I'm not mistaken, pixel vignetting is entirely due to angle of incidence on the sensor. Smaller sensors have less oblique angles of incidence at the corners. I could be wrong, but I bet that pixel vignetting won't be a factor in this comparison. I'd love to see evidence either way, though.

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1 hour ago, noone said:

I would say it does change the lens in that it becomes part of the lens as a teleconverter does.     It isn't part of the camera anyway.

It depends on how you look at it, but if you indeed look down just a teleconverter you see a smaller sensor than without, and as far as I see the converter is not part of my eye.

1 hour ago, noone said:

I believe some faster zoom lenses were actually made by adding a focal reducer to a normal lens in the lens as part of the construction.

A lot of lenses is made like that from what I have seen, in one way or another. 50mm f1.4 for example.
And some with teleconverters built in too.

1 hour ago, noone said:

In any event, this is what Metabones who makes the Speedbooster says (Speedbooster is a focal reducer).

Does cropping increase the focal length of a lens? A speedboster is just decreasing the area that the image is projected on as far as the sensor see it, or from the lens perspective it increases the area of the sensor. I'm not saying calling it a focal reducer is wrong, per say, but for me it makes more sense to look at it that way since you don't change much of the lens properties. And it removes the need to "convert" any numbers.

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3 hours ago, KnightsFan said:

@horshack If I'm not mistaken, pixel vignetting is entirely due to angle of incidence on the sensor. Smaller sensors have less oblique angles of incidence at the corners. I could be wrong, but I bet that pixel vignetting won't be a factor in this comparison. I'd love to see evidence either way, though.

Vignetting is due to the angle of incidence of light reaching the pixels on a sensor and I can't think of any reason why a smaller sensor would have less oblique angles. In fact, the higher the pixel density the more likely vignetting is to occur. BSI sensors should be less prone to this but to my knowledge neither the G5 or G5s are BSI.

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3 hours ago, no_connection said:

It depends on how you look at it, but if you indeed look down just a teleconverter you see a smaller sensor than without, and as far as I see the converter is not part of my eye.

A lot of lenses is made like that from what I have seen, in one way or another. 50mm f1.4 for example.
And some with teleconverters built in too.

Does cropping increase the focal length of a lens? A speedboster is just decreasing the area that the image is projected on as far as the sensor see it, or from the lens perspective it increases the area of the sensor. I'm not saying calling it a focal reducer is wrong, per say, but for me it makes more sense to look at it that way since you don't change much of the lens properties. And it removes the need to "convert" any numbers.

I go along with what Metabones says about their gear.

Oh and what do you think the difference will be if you look at (say) an M43 sensor through a 35mm f2 lens VS looking at it through a speedboosted 50mm 2.8 lens? (example not relying on exact match).

I will leave it there.

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1 hour ago, horshack said:

Vignetting is due to the angle of incidence of light reaching the pixels on a sensor and I can't think of any reason why a smaller sensor would have less oblique angles. In fact, the higher the pixel density the more likely vignetting is to occur. BSI sensors should be less prone to this but to my knowledge neither the G5 or G5s are BSI.

Same reason why there is less vignetting on a center crop from a full frame image. Angle of incidence becomes more oblique the farther from the center of the image.

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The issue with using faster glass on a smaller sensor to match a FF is that lenses have more imperfections the wider the aperture (F1.4 and lower usually) like color shifting, chromatic aberation, less sharp, vignetting...etc.

I am a GH5 owner and I love it, however I do believe using a larger sensor to achieve the shallow look is better than relying on faster glass.

I've used the Voigtlander 25 F0.95 extensively (version 1) and there is color shifting and fringing at F0.95.

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On 17/05/2018 at 10:34 PM, Grégory LEROY said:

Good article. What about the out of focus transition you were mentioning on your article about medium format ? Why doesn't it apply to FF vs m43.

I watch a lot of M43 pics on flickr, most of the time I find them flater than FF.

 

 

I have noticed that too on Flickr but I think it may be just a coincidence because there are more pros using FF

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On 5/18/2018 at 9:21 AM, Don Kotlos said:

Yep, perspective is only affected by the distance of the objects to the lens. The focal length & sensor size do not affect perspective in any way. A 25mm on a m4/3 sensor with an aperture of f/1.4 will have the same perspective and DoF as the 50mm on a FF sensor with an aperture of f/2.8. The other aspects of the image like distortion or busyness of the bokeh depend on the design of the lens and not the focal length/aperture/sensor size. 

I disagree about this. From what I understand, a 17mm lens is always a 17mm lens, even if it's fast and you crop it's field of view to correspond to the same field of view and DoF as a full frame 35mm lens. The way the lens renders perspective is still like a 17mm lens, which is a result of its focal length, not the field of view or the DoF. That's my understanding and I always feel that when I swap between shooting on my full frame 5D and, say an Arri (Super 35 sensor). By that I mean, a 32 or 35mm lens on an arri never truly feels the way a 50mm on my 5d does. A 50 on the arri feels like a 50 even though the field of view is different than my 5d (more like a 75 -80mm). It renders space flatter, focus falls off quickly in the way a 50 does. Different fields of view or DoF achieved with different sized sensors doesn't change the way a 50mm lens renders perspective. As I understand it.

I think the photos Andrew posted show that. The full frame shot has a steeper drop away from focus, the background has more blur (the buttons on the fax machine in the BG are a good place to look, or the text on the magazine). The full frame picture feels flatter. Even though each lens/sensor setup have corresponding depths of field.

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On 5/17/2018 at 9:33 PM, Wild Ranger said:

I don't bite on this classic argument. Perspective doesn't change (at least it shouldn't) because the camera is set at the same distance, that's why you use crop factor for measurement.

This is what I mean by depth: if you would film this with a smaller sensor and place the camera in the exact same place and try to have the same frame you would have to use a different lens, maybe a 1000mm, then the plane wouldn't look so close to the actors. 

 

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@blondini No, perspective distortion is only affected by distance from the camera to the subject. No matter what sensor/lens combination you use, if the camera and the subjects don't move, then the ratio of the size of two subjects will remain the same. I did a quick and dirty test to illustrate. It's a little imprecise (the camcorder would NOT focus on the guy in front...)

For all three images the camera is in the same place. I suspect the small discrepancies in ratio (2.2% error) are mainly due to moving parts inside the camcorder when it zooms, which changes its actual distance from the subject. But this is an easy thing to test yourself.

First image is a 4mm lens on a 1/4 type sensor

5b00484e7bf50_4mm14Type.thumb.jpg.7c78f06aa1e6595ace190a44bc2ba2bb.jpg

Second image is a 55mm lens on an APS-C sensor

5b00484a2fd15_55mmAPSC.thumb.jpg.b614ac57666d6391d1adeee070033e06.jpg

As you can see, the ratio of the figures is the same. You could even use a wider lens and the ratio remains, because the distance has not changed:

Third image is a 2mm lens on the 1/4 type sensor.

5b004a667d0a4_2mm14Type.thumb.jpg.79858286bb0e50fffd350270fc6a2454.jpg

 

Quote from Wikipedia:

Quote

Note that linear perspective changes are caused by distance, not by the lens per se – two shots of the same scene from the same distance will exhibit identical perspective geometry, regardless of lens used. However, since wide-angle lenses have a wider field of view, they are generally used from closer, while telephoto lenses have a narrower field of view and are generally used from farther away.

 

 

 

1 hour ago, Tiago Rosa-Rosso said:

if you would film this with a smaller sensor and place the camera in the exact same place and try to have the same frame you would have to use a different lens, maybe a 1000mm, then the plane wouldn't look so close to the actors.

Yes, it would. As long as the camera is in the same place, the relative size of the plane compared to the people will remain the same regardless of the lens or sensor. If you don't believe me or my Legos, go try it yourself!

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5 hours ago, Tiago Rosa-Rosso said:

This is what I mean by depth: if you would film this with a smaller sensor and place the camera in the exact same place and try to have the same frame you would have to use a different lens, maybe a 1000mm, then the plane wouldn't look so close to the actors. 

 

Yes, you have to change the lens, and that is why you use crop factor. But the camera stays in the same place and perspective wont change.

9 hours ago, blondini said:

I disagree about this. From what I understand, a 17mm lens is always a 17mm lens, even if it's fast and you crop it's field of view to correspond to the same field of view and DoF as a full frame 35mm lens. The way the lens renders perspective is still like a 17mm lens, which is a result of its focal length, not the field of view or the DoF. That's my understanding and I always feel that when I swap between shooting on my full frame 5D and, say an Arri (Super 35 sensor). By that I mean, a 32 or 35mm lens on an arri never truly feels the way a 50mm on my 5d does. A 50 on the arri feels like a 50 even though the field of view is different than my 5d (more like a 75 -80mm). It renders space flatter, focus falls off quickly in the way a 50 does. Different fields of view or DoF achieved with different sized sensors doesn't change the way a 50mm lens renders perspective. As I understand it.

I agree in part with this, but what you are talking is distortion, and not perspective. Perspective is the relation of objects in a space, that is affected buy the placement of camera. 

The distortion can happen, but i agree only in part because it depend in lot of factors as lens design, manufacture, the year and style of the lens. Remember that the classic anamorphics of the 70's has a lot of distortion compared to modern one, they look some more like wide lenses in some cases, even a 50mm.

The example of your 50mm is not that valid because a 50mm in Medium format its wide, and looks like a 30mm, obviously with the same DOF of the 50mm. 

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10 hours ago, blondini said:

I disagree about this. From what I understand, a 17mm lens is always a 17mm lens, even if it's fast and you crop it's field of view to correspond to the same field of view and DoF as a full frame 35mm lens. The way the lens renders perspective is still like a 17mm lens, which is a result of its focal length, not the field of view or the DoF. That's my understanding and I always feel that when I swap between shooting on my full frame 5D and, say an Arri (Super 35 sensor). By that I mean, a 32 or 35mm lens on an arri never truly feels the way a 50mm on my 5d does. A 50 on the arri feels like a 50 even though the field of view is different than my 5d (more like a 75 -80mm). It renders space flatter, focus falls off quickly in the way a 50 does. Different fields of view or DoF achieved with different sized sensors doesn't change the way a 50mm lens renders perspective. As I understand it.

I think the photos Andrew posted show that. The full frame shot has a steeper drop away from focus, the background has more blur (the buttons on the fax machine in the BG are a good place to look, or the text on the magazine). The full frame picture feels flatter. Even though each lens/sensor setup have corresponding depths of field.

Its always distance to subjects.

If you're shooting a 50mm on FF and s35 from the same spot, you can crop the FF image and the result will be an identical shot. This article clearly demonstrates that with two completely different FL's. 

https://admiringlight.com/blog/perspective-correcting-myth/

 

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On 5/18/2018 at 1:00 PM, KnightsFan said:

@horshack If I'm not mistaken, pixel vignetting is entirely due to angle of incidence on the sensor. Smaller sensors have less oblique angles of incidence at the corners. I could be wrong, but I bet that pixel vignetting won't be a factor in this comparison. I'd love to see evidence either way, though.

Oblique rays strike the center of the image as well as the corners.  These are aperture dependent and are called marginal rays.  The relationship between f-number and the marginal ray angle is given by f/# = sin(theta), where theta is the marginal ray angle.  So, at f/1 the marginal ray angle is 30 degrees, and so on.

The obliquity of the marginal ray does cause a form of pixel vignetting that perhaps should be called pixel apodization.  The effect is that the edges of bokeh blurs - where the marginal ray obliquity is highest - is darkened relative to the center.  The good news is that this is the definition of "good bokeh".

I think Andrew's two sample images reveal this effect.  I would guess that the bottom image was shot with the faster lens.

 

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On 5/18/2018 at 7:44 AM, OliKMIA said:

Don't forget the traditional "whaaaaat's up guyyyyyys" at the beginning of each video, along with "SUSCRIBE" with your hands pointing down toward the button.

 

Which only works for so long as YouTube doesn't move where the subscribe button is located....

 

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Andrew, thank you so much for the article. This is significant for me, since shooting is a real weight issue, and the M4T lenses and camera systems are the sine qua non when it comes to weight.

I tried to replicate your test and it worked great....but I did it with the following:
The g85, EF to MFT speed booster, and three different Rokinon T1.5 cinema lenses.

I'll say the test makes me reconsider the GH5.

I have no idea just how much light a Rokinon cine lens plus metabones speed booster yields, but it's plenty for sure---adding a variable ND filter for outside shooting would open up marvelous possibilities. 

So, here's are my questions: 1. what differences in video shooting would there be between the Voigtlander 0.95 lenses and the Rokinon cine lenses+ speed booster? 

2. Do you think the combination of the metabones speed booster plus rokinon cine lenses would be a viable alternative to using the Voiglander lenses?

Presently I own the 24, 35, 50, and 85.

Sorry my questions are perhaps a bit muddles. Can you make enough sense of them to give a response?

 

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On ‎5‎/‎19‎/‎2018 at 5:33 AM, no_connection said:

It depends on how you look at it, but if you indeed look down just a teleconverter you see a smaller sensor than without, and as far as I see the converter is not part of my eye.

A lot of lenses is made like that from what I have seen, in one way or another. 50mm f1.4 for example.
And some with teleconverters built in too.

Does cropping increase the focal length of a lens? A speedboster is just decreasing the area that the image is projected on as far as the sensor see it, or from the lens perspective it increases the area of the sensor. I'm not saying calling it a focal reducer is wrong, per say, but for me it makes more sense to look at it that way since you don't change much of the lens properties. And it removes the need to "convert" any numbers.

While it's ultimately a matter of definition as you say, it seems to me rather more natural to consider the speed booster + lens a new lens with a new focal length, than to consider the speed booster part of the sensor. Same as a wide angle front adapter or a teleconverter.

 

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Well here is a trick question to you guys, because I think not everything that has been stated here from the beginning is true. 
When talking about final aperture on a lense, you have to include the fact of which format the lens was originally made for.

Does a full frame lense of 35mm 2.8 change its aperture when you adapt it with a simple adapter (no speedbooster) to m43? No it doesn't, it will still act like a like  35mm 2.8 lens. 
And there is proof for that! If you adapt manual lenses the IBIS of the Panasonic m43 lenses only works smoothly when you set it to 35mm. 

Applying the crop factor is not as simple as stated in this article and by most of people. Watch this video as proof. 


 

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