5D / 7D - Full Frame vs. 1.6x - Pros and Cons

keep in mind the D5mk2 sensor only reads from every third line when in "live view" mode for recording video. I've yet to read a real breakdown of what the 7D does.
 
Hey Barry mentions something else in passing that I always fail to get into, but keep in mind that you also deal with a different image compression and perspective aesthetic when going from Full Frame to S35 (APS-C in our Case) Photography and Cinematography.

For me, it's MUCH easier to get most of what I'm going for as far as composition, depth compression and perspective on subject(s) with an APS-C (7D) sized sensor. Where I find myself living on a 25mm or 35mm and the sort of image it produces-- mentally trained to know exactly what I'm going to get if I'm ten inches away from a subject at minimal focus distance or ten feet away from a subject-- on an APS-C sized sensor, I always felt like I had to have a 60 or 70mm to get what I wanted out of the MKii as far as perspective goes.

A 50mm on the MKii will easily begin to distort the perspective of a subject framed head to toe, while a 25mm on a RED (while about the same focal length) looks as though the perspective is actually very different and much more natural (aka no leaning bodies or bowed lines) to my eyes.

I really dunno why, because they should look exactly the same I think? But it's something else that I struggled with as well.
 
Thank you very much Barry!


Barry_Green said:
Size of the sensor, in and of itself, has nothing to do with low light capability directly. But indirectly, it definitely does.

See, the thing that determines (or, better said, greatly influences) low light capability is the size of the individual pixels on the sensor, not the size of the sensor itself. The bigger the pixels, the more sensitive the chip will be.

Bigger sensors traditionally mean bigger pixels, because if the amount of pixels stays the same, then each pixel can be bigger. So a 1920x1080 1/3" camera like the HPX300 doesn't have nearly the same sensitivity as a 1920x1080 2/3" camera. In the 2/3" camera the same number of pixels are spread across a chip that's 4x as large, so each pixel can be 4x larger, and that lets each pixel accumulate that many more electrons, making it more sensitive.

But here's where things go wonky: what if the larger sensor has more pixels? Then each pixel will have to be smaller. So what if you were comparing a 1/3" standard-def chip against a 2/3" high-def chip? They might be the exact same sensitivity in that case. The 1/3" chip might have 1/4 as many pixels as the 2/3" chip, and the 2/3" chip has 4x as much surface area to spread them around on, so -- it nets out that the pixels are the same size, hence the sensitivity is the same.

So just by virtue of the 7D having a smaller chip than the 5D, if the pixel count was the same, that would imply that the 7D would have lower sensitivity. But because the pixel counts are *not* the same, and the 5D has more than the 7D, that means there's a chance that the sensitivity will be closer than the sensor size difference might otherwise imply.

Of course, there are other factors too, including that the 7D is a year more technologically advanced (perhaps) than the 5D, and that might allow it to deliver cleaner imagery at a higher native ISO. Or not. We'll see.

Overall, I am optimistic that the 7D might deliver low-light performance that's comparable or at least near to what the 5D can do.
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So how it is exactly in motion picture camera and academy frame ? Cause academy frame is 24mm ,canon sensor is 22mm and because of crop on canon sensor 50mm is 85mm. So on motion picture cameras there is the same crop and 50mm lens is 80mm or close ,and in reality 50mm is not 50mm or lenses for motion picture cams are made with academy frame crop in mind and 50mm is 50mm not 80mm?
 
Cinema film is rarely 24mm wide, normally it's shot at 22mm wide.

Crop factors only confuse the issue, and it's about time for them to die and forever be buried in the annals of anachronistic useless information.

The fact of the matter is: for a cinema shooter, the 7D is going to deliver the same DOF and the same FOV as a 35mm movie camera. Done. End of story. No need to worry about whether a 50mm "becomes" and 80mm, because it doesn't. Put a 50mm lens on a movie camera, and then take it off and put that lens on the 7D, and you'll have identical results (or near-enough identical that nobody's complaining.)

The only reason a "crop factor" exists is to talk about how the lens field of view compares to that of a 35mm still camera. Has nothing to do with us motion/moving image folks.
 
Thank you. I get so tired of people throwing that mess around.

Most don't have a clue on what they are talking about.....or just like to seem smart I guess.
 
Totally. That's why I started this thread. I couldn't sort through all the fiction and misconceptions regarding the topic.
 
Full Frame, as stated, really has little to do with us and I just have no idea why people keep harping about wides not being wide enough because it's not a full framed sensor. Wides have been wide enough @ 17mm or even 14mm in Cinema Application for years!

Now, you can get an SLR 11/2.8 in Tokina flavor that's excellent, and it will be plenty wide.
 
I'm still trying to understand how cropped sensors relate to depth of field, but this where I've gotten to so far. I'm still wrapping my head around these concepts, so please correct me if I'm wrong with any of this.

On a full frame, if you're shooting 50mm f/2.8 and you're 10 feet away from your subject, your depth of field will be between 9.08 ft and 11.1 ft, giving you 2.06 ft of focus.

Now when you switch over to an APS-C, if you shoot 50mm f/2.8 from 10 feet away your dof would be between 9.39 ft and 10.7 ft for 1.29 ft of focus. HOWEVER, your framing is now cropped/enlarged and it looks like you're shooting 80mm. Or you medium shot is now a med close up. IF you wanted to achieve the same framing as a 50mm on full frame, then you'd have two choices:

1. Move backwards 1.6x your distance. Now you're 50mm f/2.8, 16 feet away and your framing matches. However, since you've moved further away, your DOF changes to between 14.5 ft and 17.9 ft or 3.36 ft of focus. You've added an extra 1.3 feet of focus which may or may not be desirable. If you wanted the original framing and the same depth of field with the same lens, your only option now would be to open your iris a bit. At 50mm f/1.8, 16 feet away on the APS-C your depth of field is between 15 ft and 17.1 ft giving you 2.1 ft of focus, close to the orginal.

2. Your second option to match framing is to use a wider lens. If you put on a 31mm lens, then you'd have roughly the equivalent of the original 50mm. However, your 31mm lens will by default have greater depth of field. An an APS-C 31mm f/2.8, 10 feet away from your subject has a depth of field between 8.56 ft and 12 ft or 3.47 ft. Same problem as when you moved backwards. To get the equivalent, you'd have to open up to 31mm f/1.8.

This may or may not make a difference depending on your shooting situation. If, for example, you knew that you wanted to maintain a focal plane of 2 ft for your entire shoot, then factors of shooting distance + lens selection/speed/costs can factor in.

Something to keep in mind is that most Hollywood films are usually entirely shot at ~T2.8. (quickly looked through some American Cinematographer to confirm: Star Trek - T2.875, Terminator Salvation - T2, Julie & Julia - T2.8). This might be your goal as well. In this case, the full frame 5d2 might be a little bit more forgiving since you can be closer to your subject to achieve the same framing, which may allow you to get away with slightly slower (and cheaper) lenses.

Also, hopefully this wasn't already mentioned, but the Letus35 Extreme is 46mmx30mm, larger than the 35mm full frame size (36mmx24mm), and much larger than 24mmx18mm (academy frame size). I think that's still one of the winning things about 35mm adapters. You can zoom in and choose your framing size.
 
Just curious, so why is it that Red is pushing to offer Full Frame in their upcoming cameras if APS-C is traditional cinema?
 
The new Reds are DSMC, "Digital Still and Motion Cameras", so yes, they want "full frame" for stills. And, some folks will want to shoot motion with them to emulate 65mm/"VistaVision" cinematography.

And, some will want to use the "full frame" in a cropped Super35 mode, to get the highest quality 2.40:1 image possible for anamorphic projection.
 
jamesc said:
I'm still trying to understand how cropped sensors relate to depth of field, but this where I've gotten to so far. I'm still wrapping my head around these concepts, so please correct me if I'm wrong with any of this.

On a full frame, if you're shooting 50mm f/2.8 and you're 10 feet away from your subject, your depth of field will be between 9.08 ft and 11.1 ft, giving you 2.06 ft of focus.

Now when you switch over to an APS-C, if you shoot 50mm f/2.8 from 10 feet away your dof would be between 9.39 ft and 10.7 ft for 1.29 ft of focus. HOWEVER, your framing is now cropped/enlarged and it looks like you're shooting 80mm. Or you medium shot is now a med close up. IF you wanted to achieve the same framing as a 50mm on full frame, then you'd have two choices:

1. Move backwards 1.6x your distance. Now you're 50mm f/2.8, 16 feet away and your framing matches. However, since you've moved further away, your DOF changes to between 14.5 ft and 17.9 ft or 3.36 ft of focus. You've added an extra 1.3 feet of focus which may or may not be desirable. If you wanted the original framing and the same depth of field with the same lens, your only option now would be to open your iris a bit. At 50mm f/1.8, 16 feet away on the APS-C your depth of field is between 15 ft and 17.1 ft giving you 2.1 ft of focus, close to the orginal.

2. Your second option to match framing is to use a wider lens. If you put on a 31mm lens, then you'd have roughly the equivalent of the original 50mm. However, your 31mm lens will by default have greater depth of field. An an APS-C 31mm f/2.8, 10 feet away from your subject has a depth of field between 8.56 ft and 12 ft or 3.47 ft. Same problem as when you moved backwards. To get the equivalent, you'd have to open up to 31mm f/1.8.

This may or may not make a difference depending on your shooting situation. If, for example, you knew that you wanted to maintain a focal plane of 2 ft for your entire shoot, then factors of shooting distance + lens selection/speed/costs can factor in.

Something to keep in mind is that most Hollywood films are usually entirely shot at ~T2.8. (quickly looked through some American Cinematographer to confirm: Star Trek - T2.875, Terminator Salvation - T2, Julie & Julia - T2.8). This might be your goal as well. In this case, the full frame 5d2 might be a little bit more forgiving since you can be closer to your subject to achieve the same framing, which may allow you to get away with slightly slower (and cheaper) lenses.

Also, hopefully this wasn't already mentioned, but the Letus35 Extreme is 46mmx30mm, larger than the 35mm full frame size (36mmx24mm), and much larger than 24mmx18mm (academy frame size). I think that's still one of the winning things about 35mm adapters. You can zoom in and choose your framing size.
Click to expand...

You are absolutely right, James, and here's the main reason why I will not buy a 7D. Current APS-C lenses aren't really fast and it's impossible to achieve the T2.8 film look (I think 3.5 is the fastest) Using standard 35mm photography lenses makes it very difficult to obtain mid & wide angles so you will end up shooting further away than you would like, hence drastically changing your depth of field and visually 'compressing' the composition of your framing. Using a 7D with an adequate adaptor and cinema lenses would be an ideal situation, but I will never be able to afford a set of Cookes, Zeiss' or an Angenieux zoom...

So all things considered, the 5D, in my opinion, gives you a bit more flexibility. With enough lighting to shoot things at f/5.6-6.3 you can get closer to that film look.

P.S: The minute most APS-C lenses get anywhere near f.2, I'll be jumping the wagon.
 
Mirezzi said:
Why would you insist on using APS-C lenses in the first place with the 7D?
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It would be a waste of money to use EF lenses on a crop sensor because you lose all of the extra field of view that you were paying for in the first place. The faster EF lenses wouldn't help either because the crop sensor does not have the same low-light capabilities of the full frame sensor. Best thing to do with APS-C cameras is use the APS-C lenses that were designed for them. Unless you have the extra money for more expensive primes from Zeiss, Cooke, etc...in which case you probably wouldn't be looking to buy the semi-pro 7D model.
 
Barry_Green said:
Size of the sensor, in and of itself, has nothing to do with low light capability directly. But indirectly, it definitely does.

See, the thing that determines (or, better said, greatly influences) low light capability is the size of the individual pixels on the sensor, not the size of the sensor itself. The bigger the pixels, the more sensitive the chip will be.
Click to expand...
THANK YOU BARRY for lending the voice of authority on this matter. I try to bring it up all the time when people start talking about sensor size and low-light performance, but I can't seem to get people to listen to what should be good sense...
 
Sensor size and the number of photodiodes on the sensor are related so it does contribute to low-light capabilities. Full-frame sensors have fewer, larger photodiodes on the chip, which in turn helps the chip gather more light.

I think you need to read up on Canon's white paper on Full-Frame CMOS chips.

http://www.usa.canon.com/uploadedimages/FCK/Image/White Papers/Canon_CMOS_WP.pdf

Do a little research yourself sometimes before just quoting what someone else has said.
 
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