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Archive 2013 · Yet Another Full Frave VS Crop Sensor
  
 
fatedquest
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p.1 #1 · p.1 #1 · Yet Another Full Frave VS Crop Sensor


I'm not sure if this is the right section to post this. But I need some help understanding the difference between the two. First off, I've been spending a whole week reading about this and I'm familiar with alot of sensor size discussion and equivalence stuff.

Now, let's say we have two cameras one FF and one Crop. Both of them uses the same lens, say a 75mm at f/2 that has an image circle that circumscribes the FF sensor. Let's just imagine that the sensors and the camera are made exactly the same. The pixel density is the same too. Only the size is difference. So the FF will have more photosites that the Crop.

Here comes by statements and I want to check if my understanding is correct.

1. If both the camera take a picture from the exact same position, ISO 100, 1/100 exposure, the resulting image on the FF will have a bigger FOV (more of the scene at the edges). The perspective of the two images will be exactly the same. If the FF image is cropped, we will end up with the exact same picture. Same perspective, same exposure same DOF.

2. If the FF move infront of the Crop so that they have the exact same FOV and both of them maintain ISO 100, 1/100 exposure, the resulting image with have the same FOV but the perspective will be different. The exposure will be the same but the FF will have a shallower DOF.

3. If both the FF and Crop are in the same position, but now the crop uses a 50mm f/2. (The FF still has the 75mm f/2). The resulting image will have the same, FOV, perspective and exposure.However the FF will have a shallower DOF.

Thanks.

I'm mainly asking this because I'm trying to decide if there is any difference at all using a FF besides the DOF before I buy one.




May 24, 2013 at 04:39 PM
binary visions
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p.1 #2 · p.1 #2 · Yet Another Full Frave VS Crop Sensor


1. Yes

2. Yes

3. Not exactly. The FOV is the same, but perspective is partly affected by the focal length as well as your positioning in relation to the subject. Increased focal length will flatten or compress the image, causing subjects in the background to appear closer to the foreground. This is a great example:
http://www.photozone.de/focal-length-and-perspective

The lamp post is the same size in all of the images, but the compression of the image changes. The FF will have a shallower DOF as well, of course, because of the increased focal length.



May 24, 2013 at 06:10 PM
fatedquest
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p.1 #3 · p.1 #3 · Yet Another Full Frave VS Crop Sensor


Thank you for the link!

However those examples are a little different from my no3, I think. He changed the focal length and moved the camera to maintain the subject size. The FOV is different.

My no3 is same position with different focal length. I think it would results in the same FOV and different subject size. But the proportion of the sizes between objects remain the same(ie same perspective)

I wish I could just get my hands on a used 5D now and experiment with this.



May 24, 2013 at 06:16 PM
binary visions
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p.1 #4 · p.1 #4 · Yet Another Full Frave VS Crop Sensor


Well, right, it's not exactly what you're talking about - but it demonstrates the point, which is that a longer focal length provides compression for a scene. This is true no matter what your sensor size is.


May 24, 2013 at 06:26 PM
edl415
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p.1 #5 · p.1 #5 · Yet Another Full Frave VS Crop Sensor


While Binary Visions's example from photozone does not exactly match your question, his explanation is correct.

Why don't you rent a FF camera? 5dmk2 is only $100 to rent for 5 days.



May 24, 2013 at 06:33 PM
fatedquest
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p.1 #6 · p.1 #6 · Yet Another Full Frave VS Crop Sensor


Hmm, 100 for a few days is expensive for me. I am thinking of getting a used 5D actually and some used lenses, use it for a month or so and if I don't like it sell it off, I might lose some money there, but I like it better than renting it.

And well, as a mathematician, I'm seeing if I can solve this question that's bugging me analytically first, since I don't have a FF with me.

Basically, the bigger questions is, ignoring DOF, is there an image that can only be produced by a FF no matter what combination of focal length, aperture and distance from the focal plane we choose on a crop and vice versa.

I don't care too much about image quality since I'm already using an X E1.



May 24, 2013 at 06:45 PM
binary visions
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p.1 #7 · p.1 #7 · Yet Another Full Frave VS Crop Sensor


No. Realistically, there is essentially no image that can't be produced on a crop camera. You get a shallower DOF on a FF camera if you hold all other values equal (aperture, focal length, FOV), which is a difference, but maybe or maybe not an advantage.

My view: with FF, you get a shallower DOF and better high ISO performance, at the tradeoff of larger size and greater expense. With DX you get increased pixel density and generally smaller size/lower price, trading off some high ISO performance. Pick your poison



May 25, 2013 at 01:33 AM
 

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15Bit
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p.1 #8 · p.1 #8 · Yet Another Full Frave VS Crop Sensor


fatedquest wrote:
Basically, the bigger questions is, ignoring DOF, is there an image that can only be produced by a FF no matter what combination of focal length, aperture and distance from the focal plane we choose on a crop and vice versa.


Mathematically perhaps there is something, but probably not in a real world sense. Excluding DOF issues, what you get with FF is better dynamic range and high ISO performance due to the larger pixels (22MP on FF must have bigger pixels than the equivalent on crop). Images from FF probably scale up to print better at large sizes as the effective magnification of the upsizing (from sensor to print) is less.



May 25, 2013 at 06:12 AM
Lasse Eriksson
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p.1 #9 · p.1 #9 · Yet Another Full Frave VS Crop Sensor


fatedquest wrote:
I don't care too much about image quality since I'm already using an X E1.


If you don't care about the IQ (which I think is strange), just use a cheap crop body.



May 25, 2013 at 07:32 AM
fatedquest
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p.1 #10 · p.1 #10 · Yet Another Full Frave VS Crop Sensor


It's not that I don't care about image quality at all, but I'm now using a Fuji XE1 with old Minolta MD lenses. So I don't think IQ gets any better than that. Plus I'm not a professional. Most of my pictures just go on Facebook and the really nice ones deviantart and A4 prints.

Ive just started this hobby about 5 months ago since I got a job and can finally afford these things. I've learned that the position where I take the photo from matters alot since perspective is a function of the distance of the objects from the focal plane. So I tried all the way from 18mm to 200mm. But they don't have vintage glass for super wide angle since everything was essentially ff back then. So recently I've bought a samyang 8mm and it's fun.

That made me think whether the a FF with its extra FF will allow me to take Pictures from certain distances that a DX with any other lens won't allow me too. But now since you've told me otherwise, I'll just be happy with my xe1 and wait for fuji's ultra wides



May 25, 2013 at 01:02 PM
dsjtecserv
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p.1 #11 · p.1 #11 · Yet Another Full Frave VS Crop Sensor


Hold on a minute, let's go back to yesterday! Fatedquest, your original conclusions in all three scenarios were correct. With all due respect, binary vision is not correct about the effect of focal length on "compression". In the example linked to on Photozone, the position of the camera was moved in order to keep the size of the lamp post the same with all focal lengths. The changes in apparent relationships (compression, etc.) in the pictures is due ONLY to the change in shooting position. The focal length of a lens can only affect the framing and magnification (which are the same thing, for a given sensor size) of the image; it cannot change the size or position relationships among objects viewed from a given position. The only thing that can do that is changing viewing (shooting) position.

So for the conditions described in your #3 -- same shooting position and focus distance, different focal length to produce the same framing with different size sensors, same f-number and shutter speed -- your original conclusions are spot on: field of view, perspective, and exposure will be the same, but depth of field will be shallower for the longer full frame. The reason the the DoF is less for the full frame is not because of the size of the sensor itself, but rather the greater magnification of the longer lens needed to produce the same framing.

Disregarding image quality, noise, etc., and disregarding depth of field, then there is no reason you cannot frame the same picture in all other respects using anything from a compact point and shoot to an 8 x 10 view camera (and everything in between), assuming the availability of lenses in the appropriate focal lengths. As you correctly note, your shooting position determines the size and position relationships among the objects in the scene, while you would use focal length to frame the scene the same fore each recording medium format. Exposure would be the same in all cases. You would have difficulty producing the same depth of field in all cases, because the only variable you would have at your disposal would be the aperture of the various lenses, and they aren't likely to all have the range of f-numbers needed to produce the same DoF with their respective focal lengths. But that and image quality aside, you could produce the same pictures.

Dave



May 26, 2013 at 03:32 AM
justruss
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p.1 #12 · p.1 #12 · Yet Another Full Frave VS Crop Sensor


One other aspect of FF that I think is almost totally overlooked-- in some cases with conscious attempts to "fix": FF lenses on FF cameras are imperfect. There's light falloff, optical issues, and major differences from center to corner. In most lenses. With really strong center region performance.

I think this ends up being part of "the look" that lots of people go to FF for without being able to articulate what they're chasing. Funny part is that they push the manufacturers to fix these imperfections, with ever more correction, even light exposure, etc. In some way sterilizing the images we all look at on a day to day basis... shifting us ever more towards technical over thoughtful exposures.

I know I'm part of that problem too.



May 26, 2013 at 10:46 AM
Mike V
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p.1 #13 · p.1 #13 · Yet Another Full Frave VS Crop Sensor


Camera to subject distance defines perspective.

Focal length determines magnification.

Sensor size determines field of view.





May 29, 2013 at 08:18 AM





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