索尼相機鏡頭評測 如何減少索尼a6700 & fx30 的4k120幀模式的噪點

你是否很興奮在A6700或者FX30上測試到4K120 但很失望在相片的噪音 在這些相機中,你可以在4K120中得到更清晰的成績 讓我來給大家展示 首先,讓我簡單介紹在A6700和FX30中的4K120模式時會發生什麼 而不是在4K120中取得全6K的測試 而是在4K120中取得3840x2160的像素 因此,它給予你正確的4K或UHD4K 但要做到這一點,它不再從全面感測器下測 而是在那些像素中打進去 因此,你會得到一個大約1.5倍的測量 進入感測器來取得4K120 在這樣做中,它也會影響在感測器中已經存在的噪音 因此,它不像是給你更多的噪音 而是讓它顯得更加明顯 因為你在測試到已經存在的東西中 所以我們該怎麼處理 讓我來給大家展示 我這裡有幾張測試照片 這張是在S-Log3 S-Gamut3.Cine拍攝的 在800的低調ISO 我把它曝光為中間灰色 所以在44IRE使用灰色卡 你可以看到結果 所以它很噪音 然後,只為了笑話 這裡是2500ISO 這是S-Log3的第二個基礎 看起來像垃圾 非常噪音 而為了對比 這裡是S-Cinetone 在125ISO的低調 看起來不錯 雖然這裡還是有一點噪音 然後這裡是S-Cinetone的第二個基礎ISO 400 哎呀 也很垃圾 非常噪音 和噁心的顏色變化 所以這就是你使用基礎ISO 並正常曝光的情況 你可以嘗試幾種方式來減少噪音 第一就是在低調ISO拍攝 所以這裡是S-Log3 S-Gamut3.Cine拍攝200ISO 同樣曝光 所以在44IRE使用中間灰色 你可以看到這張照片是多麼的清晰 S-Cinetone不可能做到同樣的事情 因為它已經在125ISO的低調拍攝 另一個方法是保持在基礎ISO 所以在800和S-Log3 然後再多曝光 做到最多 然後把曝光放到後面 所以這就是你在看的 我把曝光調到中間灰色 然後我把燈打開 直到攝影機的溫度 在2點左右 然後我把曝光放到後面 調到ISO200的位置 看起來在這個情況下 ISO800被2點曝光 比ISO200更清晰 但有些範疇可能有影響 也許是ISO800曝光做得更好 也許我加了更多的燈 你可以看到背景的牆壁 曝光比ISO200曝光更明顯 但在外面的現實世界 You may hear on YouTube people recommend that you do not go to a lower than the base ISO on the Sony cameras in S-Log3 for two reasons number one and most importantly is that you supposedly lose dynamic range that you lose quality if you go below the base ISO the number two reason people will say is that you also lose access to the zebras if you see someone on YouTube who says those things but they don't actually show you comparisons or actually prove that those things are true then you can be sure that they haven't actually tried it and they're just repeating something they've heard with that said let's take a look at some more examples shot outdoors so here's a scene shot at ISO200 here's the same scene shot at ISO800 but overexposed and then readjusted in post so let me ask you do you think that there is a difference between these two shots in terms of quality and in terms of dynamic range they look very similar once the exposures have been adjusted I'm seeing very similar noise in the shadows and I'm seeing exactly the same dynamic range seeing exactly the same color reproduction and exactly the same detail in both shots and if they're not exactly the same the differences are so minuscule that they don't matter especially if you're not AB comparing two different shots what I think happens instead of losing dynamic range as you shift the ISO whether you go below the base or above the base is the amount of dynamic range isn't changing but where that dynamic range is sitting is what actually changes you just imagine that the dynamic range of the camera is a bucket or some kind of container of a box or something there's all this dynamic range that is possible to capture but of course the camera can't capture all of it so the box is sitting in a very specific range of what's possible to capture at the base ISO here it is if you lower the base ISO the bucket doesn't get smaller the box doesn't get smaller it just moves down so you have less dynamic range that you can capture in the highlight areas but you get more dynamic range in the shadows if you go above the base ISO again the box or the bucket doesn't shrink it just moves higher so you can capture more dynamic range in the highlights but less dynamic range in the shadows this isn't true for every possible ISO value in the camera because of course the higher you go the noisier it gets the more the color shifts but I think within a reasonable amount of dynamic range around that base ISO this is true as I've shown you and hopefully convinced you the results between shooting in 800 overexposed by as much as two stops versus shooting in ISO 200 are essentially equal so which one should you do for me it's just a lot easier to go ahead and lower that ISO to 200 because what I'm seeing on the LCD is what I'm actually going to capture and that allows me to just monitor with my eyes how bright I want the exposure to be not only that I can use my zebras at the clipping point so that I'm making sure that I'm capturing as much highlight information as possible in my clipping highlights if I can versus shooting in ISO 800 and then overexposing so for that you are relying on the meters and the camera to tell you how much you're overexposing the scene by you also want to make sure that you're paying attention to whether that number is blinking or flashing or is solid the number won't ever go above plus 2 but if it's plus 2 and it's flashing that means you're overexposed you want to make sure that it's a solid plus 2 or lower with this scene that I'm showing you here the camera was around a plus 1.7 to a plus 2 but never flashing plus 2 you're also looking at an image on your LCD or your viewfinder that is plus 2 or plus 1.7 stops overexposed than what you actually want it to be that's why I think it's easier just to go ahead and capture at the lower ISO but regardless the results should be very similar if not identical if you do have the FX30 you also have another option which is to use Cine EI I don't want to get into the specifics of that in this video it's too complex I've got another video that goes into pretty good detail about how it all works so check that out if you need to know real quick another reason people tell you not to go to the lower than base ISO is because the zebras go away and that's also not true what happens like I mentioned is the allocation of dynamic range shifts downward so that clipping point is no longer the same as it is at ISO 800 so if you have your zebras set to say 98 which is the clipping point at ISO 800 in S-Log3 and then you go down to ISO 200 the zebras disappear because the clipping point is no longer at 98 it's going to be lower I don't know off the top of my head what that is but in order to find out point your camera at a bright light source the sky, a light, whatever something that will actually clip and then go into your zebra menu go to custom zebra custom 1 or custom 2 then set it to lower limit and then lower the value until the zebras come back there's your new clipping point you can do that for any picture profile and any ISO in the camera to find the clipping point people are undoubtedly going to ask what do I do in low light situations well don't shoot 4K 120 in low light situations what I've shown you here is that you really need as much light as possible to overexpose that sensor so that you can bring the noise floor down if you have a normal exposure at ISO 800 the noise is visible so what we're doing is lowering that noise floor we're burying the noise in the shadows which is what essentially happens at ISO 200 by default and then what we're doing when we overexpose ISO 800 and then bring down the exposure we're smooshing down the noise floor so we can't see it anymore if you can't overexpose the sensor then you can't lower the noise floor so you're going to have noisy footage what people obviously want to do when they can't add light to the sensor or their aperture is already maxed out and their shutter can't go any lower is they boost the ISO and as we know the base ISO is already noisy so boosting the ISO is only going to make it noisier and noisier so there are definite limitations to 4K 120 in the a6700 and the FX30 but try to take a glass half full perspective as opposed to a glass half empty and look for opportunities where the 4K 120 is going to benefit you obviously you have a massive crop in comparison to full frame it's more like a three times crop look for situations where you need a long lens where you can't get close to whatever it is you're trying to film also why are you even shooting in 4K 120 to begin with you need something that's going to be interesting something that's dynamic enough that when you slow it down by eight times that it actually looks really cool not every scenario is going to call for 120 frames slow motion sometimes 60 is going to be more than enough and in 4K 60 you're not dealing with that massive crop hopefully that all makes sense and if you have any questions please leave them in the comments and also if there's anything else about the a6700 or the FX30 that you would like to know please let me know in the comments that would be super helpful as always I really appreciate you watching the video and maybe I'll see you in another one