Prime Lens Size for 1920x1080

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Derfla

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Prime Lens Size for 1920x1080

PostTue Feb 23, 2021 5:10 pm

I do realize that this falls under the category of "stupid question", but I am having a massive brain fart.

I am currently using a Sony a6400 with a Sony 18-105mm zoom lens for giving speeches on Zoom at 1920x1080. I am finding that I leave the lens set to 52mm all the time.

I would like to start using my Ursa Mini Pro G2 with a prime lens for this work. Factoring in the crop sensor, what equivalent size prime lens do I need?
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rick.lang

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Re: Prime Lens Size for 1920x1080

PostTue Feb 23, 2021 5:18 pm

Are you currently using a window (crop) of the APS-C sensor to get to 1920x1080 or are you using the full sensor readout? On the UMProG2, do you want to use a window or the full sensor readout?
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Re: Prime Lens Size for 1920x1080

PostTue Feb 23, 2021 5:39 pm

rick.lang wrote:Are you currently using a window (crop) of the APS-C sensor to get to 1920x1080 or are you using the full sensor readout? On the UMProG2, do you want to use a window or the full sensor readout?


Hi Rick, great questions, and here is where my noobie ignorance comes in so please bear with me. I typically shoot in BRAW, so the Window Sensor by default is on. However, I would like to try Prores, so I guess the answer is both? It looks like I would need to consider two prime lens sizes.

I do not record the Zoom meetings on the UMProG2. I hope this helps.
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Re: Prime Lens Size for 1920x1080

PostTue Feb 23, 2021 6:14 pm

I have looked at the specs from Sony and they don’t seem to indicate whether HD recording is from the whole sensor or a window. It took awhile to find the dimensions of the sensor from the specs other than APS-C. No wonder I like BMD because their spec pages are precise. I know the 4K images are produced from oversampling so I’ll assume the HD are also oversampled from a crop of about 1.53x (36mm/23.5mm) like Nikon DX APS-C. The full sensor on the UMProG2has a crop of 1.42x; let’s assume you are oversampling from the full sensor as well. so the field of view on the G2 is about 1.078x wider. if you currently like a 52mm focal length, on the G2, you’ll like a 56mm focal length. Not much difference if my assumptions are correct.
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Re: Prime Lens Size for 1920x1080

PostTue Feb 23, 2021 7:04 pm

rick.lang wrote:I have looked at the specs from Sony and they don’t seem to indicate whether HD recording is from the whole sensor or a window. It took awhile to find the dimensions of the sensor from the specs other than APS-C. No wonder I like BMD because their spec pages are precise. I know the 4K images are produced from oversampling so I’ll assume the HD are also oversampled from a crop of about 1.53x (36mm/23.5mm) like Nikon DX APS-C. The full sensor on the UMProG2has a crop of 1.42x; let’s assume you are oversampling from the full sensor as well. so the field of view on the G2 is about 1.078x wider. if you currently like a 52mm focal length, on the G2, you’ll like a 56mm focal length. Not much difference if my assumptions are correct.



Thank goodness for smart people, thanks! :) So basically I'll be looking at a 50mm prime. I say this because I am looking specifically into the DZOFilm Vespid Lenses (I really like their Zoom lenses). It looks like that's the closest.

As a side note, I also want to research why BRAW forces the Window Sensor to the on position. I have read how BRAW is better for editing/coloring, so to be honest, I never messed with ProRes. It seems that you get more out of your zoom lenses using ProRes.
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Re: Prime Lens Size for 1920x1080

PostTue Feb 23, 2021 10:00 pm

On the 4.6K family, raw recording requires a window or crop of the sensor. But ProRes gives you some options of shooting with the full sensor readout even though you can record your file in a smaller resolution; or you can use a window if you prefer.
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Re: Prime Lens Size for 1920x1080

PostWed Feb 24, 2021 9:28 am

And since that camera offers you all the options in ProRes, you are very flexible. There is not that much difference between BRAW and ProRes 444.
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Re: Prime Lens Size for 1920x1080

PostWed Feb 24, 2021 1:37 pm

A question for Rick/Uli,

You guys are much more experienced than I am. Thanks so much for your responses!

In terms of video quality, is there an advantage to shooting with a full sensor versus a cropped sensor? I do understand about the crop factor/aspect ratio/framerate/FOV. I am just wondering about the overall quality of the video (clarity, depth, etc.)
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Re: Prime Lens Size for 1920x1080

PostWed Feb 24, 2021 2:44 pm

Sure there is. A Bayer-pattern sensor can't really resolve the number of pixels it has. Oversampling is a good thing for the quality of your final images. Sampling UHD and scaling down to HD will always look better than shooting 1:1. That's also the reason to have 4.6K pixels instead of just 4K, so you get at least some oversampling. Or shooting 6K when there is no display in the world showing that resolution.
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Re: Prime Lens Size for 1920x1080

PostWed Feb 24, 2021 2:57 pm

Uli Plank wrote:Sure there is. A Bayer-pattern sensor can't really resolve the number of pixels it has. Oversampling is a good thing for the quality of your final images. Sampling UHD and scaling down to HD will always look better than shooting 1:1. That's also the reason to have 4.6K pixels instead of just 4K, so you get at least some oversampling. Or shooting 6K when there is no display in the world showing that resolution.


Again, please forgive my lack of experience/knowledge in this field. Are you saying:

A) Full Sensor = better video quality

or

B) Cropped Sensor = better video quality
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Re: Prime Lens Size for 1920x1080

PostWed Feb 24, 2021 5:43 pm

Uli is recommending you use the full sensor readout (or UHD readout) in the camera but you can record HD to your media file in the camera. That will give you better colour and potentially better detail compared to using a HD crop of the sensor and recording HD.

On the Menu / Record first page you can set the camera to record ProRes HD and from the next page you can specify to set the Sensor Area to either 4K or a crop of 2.6K do you are oversampling sensor data. If you set the Sensor Area to HD, that means an HD crop which has no oversampling benefits.

If you want the widest field of view then set the Sensor Area to 4K, but if you want your subject to appear ‘closer’ to the camera then set the Sensor Area on the camera to 2.6K (which is similar to the look of a traditional Super 16 recording).
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Re: Prime Lens Size for 1920x1080

PostWed Feb 24, 2021 7:44 pm

If you have an IPhone, you might find this app very useful & convenient to have on set, let alone it's very cheap at $11. They have thousand of cameras and lenses in their database and does a fair job keeping up with new ones.

https://www.cined.com/f8-lens-toolkit-i ... culations/
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Prime Lens Size for 1920x1080

PostWed Feb 24, 2021 7:59 pm

Ellory, does that depth of field feature include user defined circle of confusion options applicable to the camera’s sensor they support?

I still use user interface of the app Angle of View that allows several different cameras or sensor windows to be defined on the front page so I can very quickly compare my cameras and lenses. Unfortunately it’s not been updated in years so I keep an old phone just to use the app. I’ve never seen anothet app with that one click easy interface to change your reference to the cameras and windows you use.
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Re: Prime Lens Size for 1920x1080

PostThu Feb 25, 2021 4:55 am

rick.lang wrote:Ellory, does that depth of field feature include user defined circle of confusion options applicable to the camera’s sensor they support?

I still use user interface of the app Angle of View that allows several different cameras or sensor windows to be defined on the front page so I can very quickly compare my cameras and lenses. Unfortunately it’s not been updated in years so I keep an old phone just to use the app. I’ve never seen anothet app with that one click easy interface to change your reference to the cameras and windows you use.


Rick, I have an older version of the F8 called Lens Matcher (which is amazing). On the previous version, it did not have such options. I'm going to do the update when I get back to SoCal and I'll let you know. The developer is very responsive with emails too so if you want to inquire directly, their contact is posted on the App Store page for the F8.
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Re: Prime Lens Size for 1920x1080

PostThu Feb 25, 2021 4:56 am

Thanks, Ellory.
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Ellory Yu

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Re: Prime Lens Size for 1920x1080

PostThu Feb 25, 2021 2:57 pm

rick.lang wrote:Ellory, does that depth of field feature include user defined circle of confusion options applicable to the camera’s sensor they support?

Rick, As I said I'm looking to update my app with the latest version of F8 when I get back to SoCal this weekend. However I just found out that my old phone OS which I am using for the Lens Matcher is too old to be upgraded, therefore I might not be able to get F8 installed on it. Lens Matcher, for my own need, is good enough and an awesome app but I understand F8 has the latest and greatest bells and whistles. Having said that, I did contact their support to ask about this. Here is what they replied and I hope this gives you the answer to your question.

The Circle of Confusion is automatically calculated based on the active sensor size. You cannot enter a custom circle of confusion directly, but you can adjust the formula that calculates it: In the top menu, go to "Settings" (last item). There you'll see a "Circle of Confusion Formula" setting. By default it is set to d/1500, which is the most commonly used value, but you can change it if you have different requirements. See screenshot.
circle_of_confusion.PNG
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Re: Prime Lens Size for 1920x1080

PostThu Feb 25, 2021 4:32 pm

rick.lang wrote:Uli is recommending you use the full sensor readout (or UHD readout) in the camera but you can record HD to your media file in the camera. That will give you better colour and potentially better detail compared to using a HD crop of the sensor and recording HD.


I think I am getting the hang of this. So for "regular" shooting, I understand the advantages of what you posted above.

Specifically for Zoom however, there are limitations. I am basically going to be using the UMProG2 as a glorified webcam :roll: I will not be recording. At least this way with COVID still lingering, It doesn't have to sit in its case doing nothing.

Here is my workflow:
UMProG2 > Bidirectional HDMI/SDI 3G Micro Converter > ATEM Mini Pro > Macbook Pro > Zoom

With this setup I cannot select UHD since Zoom doesn't recognize that resolution. It looks like the highest resolution I can select is 2k 16:9 2048x1152. I can select any codec. In this case I am going with 444.

Are my assumptions above correct regarding Zoom? I ask because I am a bit confused as to why I can't select UHD or any resolution higher than 2k. Shouldn't the oversampling kick in if I were select a higher resolution which in theory would give me better quality? I do realize that using the UMProG2 as a webcam is blasphemy, but I do do get a lot of compliments regarding the quality of my video :D
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Re: Prime Lens Size for 1920x1080

PostThu Feb 25, 2021 4:54 pm

I think you’ll be fine using HD or the 2K resolution if that works with Zoom.
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Re: Prime Lens Size for 1920x1080

PostThu Feb 25, 2021 4:56 pm

Ellory, you’re so kind to inquire. Yes, access to the formula for CoC is fine. I use 1730 instead of 1500 in the formula for the app I use, but f8 is much more fully featured.
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