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Must watch video on full frame vs crop cameras. "Full frame look" covered.


KarimNassar
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He's right and he's wrong. It depends on what you think f-stops are telling you. If you think they are telling you depth of field, he is right. If you think they are telling you how to expose, he is wrong. Look at how he has to change the ISO to get the images above. A M43 f/2.8 will expose about the same as a full-frame f/2.8. But if you are buying lenses to get shallow depth of field, then you have to use the multiplier on the aperture, just like you do on the focal length to compare field of view.

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He's right and he's wrong. It depends on what you think f-stops are telling you. If you think they are telling you depth of field, he is right. If you think they are telling you how to expose, he is wrong. Look at how he has to change the ISO to get the images above. A M43 f/2.8 will expose about the same as a full-frame f/2.8. But if you are buying lenses to get shallow depth of field, then you have to use the multiplier on the aperture, just like you do on the focal length to compare field of view.

 

Actually he covers that in the video as well.

According to him 100iso on full frame is not equivalent to 100iso on m4/3, you have to adjust the iso by multiplying by the crop factor square.

And this is what he did to match the 2 images.

He goes in depth regarding this in the video I encourage you to watch it.

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There's some flaws in his arguments.

 

Yes the bigger sensor the more surface area there is to catch light. But that light is being used to cover a wider area of view. Therefore an f1.8 native APS-C lens gives the same amount of light to an APS-C sensor as a f1.8 native FF lens would give to a full frame sensor.. So although optically/mechanically the two lenses don't have the same aperture, the light given to the sensors is still the same. IE. If you put an f1.8 lens designed for a crop sensor on to a full frame sensor, the exposure would be the same as an f1.8 FF lens, but there would be a black circle because the light from this crop lens doesn't cover the full frame sensor.

 

Also I don't know why he singles out the mirrorless camera makers of not marking their lenses "correctly" when Canon and Nikon do exactly the same thing for their crop camera lenses.

 

Honestly, I think noise levels come down to design quality. If you look at the dpreview studio comparison shots, you can see there's a large variation in noise level even between different full frame cameras.

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Referring to the video. It has more holes in it than a block of swiss cheese.

 

He says a large sensor captures more light, without mentioning the crucial SIZE and NUMBER of pixels. It is the size of the pixels and how many there are that gives you your resolution and dynamic range. The Blackmagic Production Camera for instance has a larger sensor than the GH4 but sucks in low light because it has small photosites due to global shutter circuitry around each pixel taking up a lot of room. He has grossly oversimplified things in that video through lack of basic knowledge.

 

He is multiplying aperture by crop factor to give an equivalent depth of field, this too is bollocks.

 

F1.2 is F1.2. At the same focus distance and focal length you will get the same shallow DOF with a 50mm F1.2 on a small sensor as you would do on full frame. The difference is that to maintain the same framing, the small sensor camera has to move back from the subject, and the focus point shifts backwards towards infinity, which lessens the separation between the subject and background making it appear that the lens is giving a less shallow DOF.

 

He also really stupidly in his Canikon love affair doesn't seem to mention that F1.2 is as bright as F1.2 no matter what the sensor size is.

 

F1.4 does not = F2.8 with a 2x crop sensor in terms of exposure or light transmission.

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Speedboosters compensate for this as you do not lose the light that would have fallen outside of the crop sensor.

Which means by using them you will get the same look as full frame as the field of view is matched and the light loss taken care of.

But you do not gain light, you stop losing it, compared to the full frame sensor.

 

This is also false.

 

Speed Booster works by brightening the image projected at the sensor. The light from the lens is concentrated into a smaller area. It has nothing to do with how far you crop into it. If you took the centre of the image in photoshop and cropped it, you do not 'lose light' and the image does not darken does it!??!

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Referring to the video. It has more holes in it than a block of swiss cheese.

 

He says a large sensor captures more light, without mentioning the crucial SIZE and NUMBER of pixels. It is the size of the pixels and how many there are that gives you your resolution and dynamic range. The Blackmagic Production Camera for instance has a larger sensor than the GH4 but sucks in low light because it has small photosites due to global shutter circuitry around each pixel taking up a lot of room. He has grossly oversimplified things in that video through lack of basic knowledge.

 

That is also one of the first things I first thought about, he answered this with his thought process in the comments here:

 

"Pixel density doesn't impact total light gathered or overall image quality, which is why I didn't feel the need to address it in this video. Pixel density does determine the noise level per pixel, but that's only relevant for comparing different sized sensors if you choose to view them on a pixel-by-pixel basis rather than keeping the image size constant and scaling the pixels as needed. Because yours is a common question, I am planning a future video to address pixel density.And I do say in the video that all comparisons assume similar sensor technology, and most modern sensors do have pretty similar total image quality."

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This is also false.

 

Speed Booster works by brightening the image projected at the sensor. The light from the lens is concentrated into a smaller area. It has nothing to do with how far you crop into it. If you took the centre of the image in photoshop and cropped it, you do not 'lose light' and the image does not darken does it!??!

 

You are talking about "density of light"/"density of photons" (number of photons per unit of surface).

He is talking about total light gathered by the lens (all photons, no mater where you send them - on 1,2 or 3 inch square surface): his "lose light" means "lose photons", and these lost photons belong to the lost part of the image.

 

The same he said on the beginning in ISO section. He said, that ISO definition as "density of light" is misleading, and he is talking later always about "total light gathered by the lens" as more appropriate in his opinion.

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"Speedboosters compensate for this as you do not lose the light that would have fallen outside of the crop sensor.

Which means by using them you will get the same look as full frame as the field of view is matched and the light loss taken care of.

But you do not gain light, you stop losing it, compared to the full frame sensor."

 

This is also false.

 

Speed Booster works by brightening the image projected at the sensor. The light from the lens is concentrated into a smaller area. It has nothing to do with how far you crop into it. If you took the centre of the image in photoshop and cropped it, you do not 'lose light' and the image does not darken does it!??!

 

I disagree and I believe it to be true, this is what I mean visually by what I said, there is the same amount of light let through by the lens on all 3 examples:

 

speebooster.jpgnow if I am still wrong then I have completely misunderstood speedboosters from the start.

 

let me know

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I am shocked and appalled at how terrible the information in that video is (and I want my 37 min of my life back). 

 

What makes it worse is that he is actually presenting it with such arrogance and conviction, that people are buying into it!

 

Karrim, let me take a moment to explain:

 

If you take a picture on a 7D (APS-C crop) vs a 5D (Full Frame) with the same 50mm lens, the 7D only sees the center part of that lens. If you were to take that picture from the 5D and crop it inward 1.6x in post, it should look pretty much identical to the 7D's picture. Same bokeh, same DOF, same amount of light exposure. The difference is only that you are cropped inward so much that you might not be able to get your entire subject in the frame anymore.

 

The aperture does not change on a crop sensor camera. PERIOD. However, you have to stand farther away from your subject to get what you want to fit inside the crop. Since DOF is a combination of aperture and distance, the DOF will change and become deeper as you step back more. But again, the aperture does not change! Only your distance has. A picture taken at the same distance will have the same DOF, and most importantly the same amount of light!

 

The reason the manufacturers list "35mm equivalents" on their lenses is not at all misleading. Many photographers think in full frame FOVs, so they need to know that a 28mm is no longer a wide angle, but rather a medium one. The amount of light gathered does not change, the aperture is very much the same. But your composition is different, as you are standing farther away. F/2.8 at a particular distance to your subject will yield the same DOF no matter what size the sensor is. What Northup is saying is PATENTLY FALSE.

 

As far as light gathering with a speed booster- imagine you have a flashlight, and shine it at a wall. As you get closer to the wall, the photons are less scattered, closer together, smaller and brighter. If you've ever tried to fry ants on a sidewalk with a magnifying glass, you know how a focal reducer can condense the light from the sun into a single spot intense enough to start a fire. So when using a speedbooster, you are actually gaining more light, technically more than a full frame camera with the same lens would as it is more condensed now. This is science, this is physics of light, and has been totally explained to death before. 

 

As an aside- his whole thing about smaller sensors having poor low light performance because they see less light overall. I'm with Andrew- total and complete bullocks. The size of the sensor overall has NOTHING to do with it, but rather the size of the photosites. The photosites are what make up the individual pixels for your image. The higher the megapixels, the more densely populated the sensor is and therefore the smaller each photosite. Smaller photosites gather less photons per exposure and therefore get noisier at similar ISO values to larger ones. But technically, you can have a small sensor with larger photosites than a larger one. The Sony A7S how shown what a difference smaller megapixel counts can do for a sensor in low light. Technically Panasonic can make a MFT sensor especially designed for low light by only making it 10 megapixels. Then we'd get stellar ISO performance compared to any 5D, despite sensor size. 

 

He keeps going on about how because the sensor is smaller than a full frame one, it can't see as much light and therefore the ISO needs to pump up the gain higher to reach the same exposure. Everytime he says that I want to shove my fist through the computer screen for being so arrogantly ignorant. 

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I quite liked this video i have to say.  A lot of it I found a bit pointless, but it prompted me to reconsider and re evaluate how I consider some of the factors he discusses.  His point about having to factor the sensor crop into the lens equivs is valid, but I think he disregards the fact that most of us know a 12-35mm f2.8 lumix will never create the same image as a huge 24-70 2.8 on full frame.   

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I disagree and I believe it to be true, this is what I mean visually by what I said, there is the same amount of light let through by the lens on all 3 examples:

 

speebooster.jpgnow if I am still wrong then I have completely misunderstood speedboosters from the start.

 

let me know

 

In case anyone TL;DR my explanation above, the 1st and 3rd have the same intesity of light hitting the sensor at a time (the guy in the video wants to say the cropped one does not. But that's because he's ignorant). But the middle one does not- it is brighter than the others because in reducing the image, the photons are also condensed (less scattered) which results in more intense light. 

Just like a flashlight or projector that is farther away / closer to a wall. The smaller the light gets, the more intense and vice versa. 

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He keeps going on about how because the sensor is smaller than a full frame one, it can't see as much light and therefore the ISO needs to pump up the gain higher to reach the same exposure. Everytime he says that I want to shove my fist through the computer screen for being so arrogantly ignorant. 

 

You've misunderstood his point.  He is saying that the iso you're seeing displayed on the lcd screen is no longer a tangible figure due to the fact that inside the camera the sensor may be being ragged harder to obtain the same exposure (assuming photosites are similar size).  This is something I had never considered.  The fact that on ex tele mode on the gh2 or on aps-c crop mode on my A7R the noise levels are greater would go some way towards backing up his statements

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