Crop v FF

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Archive 2010 · Crop v FF

andrew81
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p.1 #1 · Crop v FF

Not your typical "should I buy this" thread. Having had a loom at several hundred different examples of shots taken with a full frame 5dmkII v my 1dmkII I can clearly see the out of focus area when using the FF camera is WAY more out of focus. Bokeh isn't it??
Why?? Same lens etc etc.

Sep 08, 2010 at 09:59 AM

Mike V
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p.1 #2 · Crop v FF

Shorter subject distance?

Sep 08, 2010 at 10:11 AM

ChrisDM
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p.1 #3 · Crop v FF

The greatest factor in creating out of focus backgrounds is the relationship between subject distance and background distance relative to the camera. And of course this info is not in the EXIF data so without these variables also being equalized no relevant conclusions can be made. But I can tell you as the owner of many crop (1.6x and 1.3x) cameras and a few full frame cameras, the crop factor (or lack thereof) plays a much smaller role than subject/background distance. Wide open fast apertures also help

Sep 08, 2010 at 02:11 PM

Omnicolor
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p.1 #4 · Crop v FF

Welcome to the club

http://www.fredmiranda.com/forum/topic/933906/0#8820996

Sep 08, 2010 at 02:26 PM

Sami Ruusunen
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p.1 #5 · Crop v FF

Camera crop factor doesnt change the bokeh at all. Only the distance from the subject and used lens does. Although you can sometimes get closer to subject with ff camera.

Sep 08, 2010 at 02:35 PM

jamesf99
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p.1 #6 · Crop v FF

Besides subj-background-camera distance variability, the lens (FL) used will also make a difference.

Sep 08, 2010 at 02:50 PM

Alan321
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p.1 #7 · Crop v FF

For the same size subject as a portion of sensor size, the bigger sensors will give you less DOF in your prints. On one hand you need less enlargement, which contributes to greater DOF, but that is swamped on the other hand by having to use a longer focal length or a smaller shooting distance.

Compared to a 1D2, the 5D2 has a nominally 1.3x bigger sensor in each direction. This means less enlargement by a factor of 1.3 and hence 1.3x the DOF - if that was all there was to it. This is just the sensor-size contribution to DOF.

To get the subject to fill the image sensor by the same percentage you need to use a focal length 1.3x longer on the 5D2 than with the 1D2 *OR* you'll reduce the shooting distance by a factor of 1.3. DOF is inversely proportional to the square of the focal length and so it increases by 1/(1.3x1.3)=1/1.6. DOF is also proportional to the square of the shooting distance and so it increases by 1/( (1/1.3) x (1/1.3)) =1/1.6. Either way, you get the same reduction of DOF by a factor 1.6.

Combine the two effects and you get DOF increases by 1.3 and decreases by 1.6, or overall decreases by 1.3.

Note that I've used 1.3x1.3=1.6. The reason is that the 1.3 field of view crop factor for the 1D2 is actually more like 1.26 than 1.3, and 1.26x1.26 is close to 1.6.

- Alan

Sep 08, 2010 at 03:25 PM

gdanmitchell
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p.1 #8 · Crop v FF

andrew81 wrote:
Not your typical "should I buy this" thread. Having had a loom at several hundred different examples of shots taken with a full frame 5dmkII v my 1dmkII I can clearly see the out of focus area when using the FF camera is WAY more out of focus. Bokeh isn't it??
Why?? Same lens etc etc.

Larger formats provide shallower DOF. The OOF area is sometimes called "bokeh." But be aware that it is hard to make such a generalization by viewing lots of photos online.

Sep 08, 2010 at 03:53 PM

Lance Lee
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p.1 #9 · Crop v FF

It has been said, but I'll try it another way.

With the 5D, in order to get the same framing as with the 1D2, you will have to either get closer, use a longer focal length, or a combination of both. When you do that the background gets more blurry, if using the same aperture.

When I went from 40D to 1D2, I was a bit worried about the reduced DOF at my favourite aperture, 2.8 1/2. I was pleasantly surprised to find that it wasn't a problem, the 1D2 is actually better at placing the focus point that I'm getting more in focus with the 1D2 than the 40D.
Said another way, with similar framing and at 2.8 1/2, the 1D2 has a more pleasing, more blurred background, AND it has more of the subject in focus. I wouldn't believe it if I wasn't doing it.

Sep 08, 2010 at 03:54 PM

kakomu
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p.1 #10 · Crop v FF

gdanmitchell wrote:
Larger formats provide shallower DOF.

This isn't true in the least. In fact, if you look at DoF calculators, if you have a constant focal length, aperture and distance from the subject and just measure the DoF between an APS-C sensor and a full frame sensor, the APS-C sensor will have a SHALLOWER DoF.

DoF is based upon "acceptable sharpness" which revolves around the concept of a circle of confusion (CoC). Measurement is based upon typical human eye acuity and the ability to discern detail on an 8x10 print from 10-12 inches away. You divide the smallest detail a human can discern by the magnification of the medium (e.g. 35mm = 8x magnification to 8x10. APS-C is larger) and you arrive at the largest circle of confusion that you can have on that medium to be considered acceptably sharp. With 35mm, the common value is 0.03mm. With APS-C, the common value is 0.019. The smaller circle of confusion required for sharp prints on APS-C shrinks the DoF.

Now, the reason why you get a shallower DoF with a full frame camera is because the medium dictates the angle of view of a given focal length. Given a specific focal length and a need to frame a subject a specific way, you will have to get closer to the subject with a full frame camera than you would with an APS-C camera.

By shrinking the distance between camera and subject, you can shrink the DoF. The actual DoF isn't always shrunk by a large margin, but by getting closer to the subject, the background tends to be significantly more blurry.

Sep 08, 2010 at 06:15 PM

andrew81
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p.1 #11 · Crop v FF

kakomu wrote:
gdanmitchell wrote:
Larger formats provide shallower DOF.

By shrinking the distance between camera and subject, you can shrink the DoF. The actual DoF isn't always shrunk by a large margin, but by getting closer to the subject, the background tends to be significantly more blurry.

I was sure I read somewhere that larger formats give a shallower DOF but the distance thing seems more plausible and logical though.

There goes my justification for a 5D lol Might just buy myself a new prime lens.

Sep 08, 2010 at 08:35 PM

Lance Lee
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p.1 #12 · Crop v FF

andrew81 wrote:
kakomu wrote:
gdanmitchell wrote:
Larger formats provide shallower DOF.

By shrinking the distance between camera and subject, you can shrink the DoF. The actual DoF isn't always shrunk by a large margin, but by getting closer to the subject, the background tends to be significantly more blurry.

I was sure I read somewhere that larger formats give a shallower DOF but the distance thing seems more plausible and logical though.

There goes my justification for a 5D lol Might just buy myself a new prime lens.

I think there is a lot of confusion on this subject, because there are two things going one, the physics of it and the practical part of it.
Technically the format doesn't effect DOF, but in practice the size of your sensor/film will effect your DOF and background blur. Both are true.
I think the biggest thing you would notice is how the camera's work. In some ways the 5D interface is more straightforward, but I've found in practice I'm far more comfortable with the 1D2 than 5D/40D/20D, etc. Then there is the AF system, which is night and day different.

Sep 08, 2010 at 08:48 PM

kakomu
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p.1 #13 · Crop v FF

Lance Lee wrote:
I think there is a lot of confusion on this subject, because there are two things going one, the physics of it and the practical part of it.
Technically the format doesn't effect DOF, but in practice the size of your sensor/film will effect your DOF and background blur. Both are true.
I think the biggest thing you would notice is how the camera's work. In some ways the 5D interface is more straightforward, but I've found in practice I'm far more comfortable with the 1D2 than 5D/40D/20D, etc. Then there is the AF system, which is night and day different.

Technically speaking, the format dictates the DoF as DoF is a concept based upon how a final image looks, whether it's printed or viewed on a monitor.

Lenses have a two dimensional plane of focus, which means there's absolutely no thickness. Given a lens with no medium, all you can measure is the distance from the lens where absolute focus is achieved and the maximum cone of light that can enter or exit the lens. The medium is necessary to determine the characteristics of the DoF for a given lens.

andrew81 wrote:
I was sure I read somewhere that larger formats give a shallower DOF but the distance thing seems more plausible and logical though.

There goes my justification for a 5D lol Might just buy myself a new prime lens.

The problem with most discussions about DoF and camera sensor size is that the variables are NOT controlled very well in the discussion. Most discussions on DoF attempt to either maintain angle of view or framing of a subject. So, between two cameras with different mediums, multiple factors will be adjusted at the same time.

If you attempt to adjust the camera to maintain framing, you'll change the subject to camera distance. If you attempt to maintain the angle of view, you'll change the focal length. With uncontrolled variables comes a bunch of confusion on the subject and unscientific conclusions.

In general, all things remaining the same, a smaller format will have a shallower DoF. However, in practice, this shallower DoF is typically canceled out by all of the other factors that you would change in order to take a picture with a crop format. E.g., by standing further away from the subject, you increase DoF. By using a shorter focal length (35mm on Crop, vs. 50mm on full frame), you increase DoF. It's these factors that account for the increased DoF that you encounter with a crop camera over a full frame camera.

Edited on Sep 08, 2010 at 10:59 PM · View previous versions

Sep 08, 2010 at 09:35 PM

Omnicolor
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p.1 #14 · Crop v FF

Very good explanation! Last sentence though,,,,, other way around?

kakomu wrote: It's these factors that account for the increased DoF that you encounter with a full frame camera over a crop camera.

Sep 08, 2010 at 10:13 PM

SamirD
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p.1 #15 · Crop v FF

I think a good way to look at this is to compare to the high-end of the point and shoots. Bokeh is nearly impossible to achieve on these cameras because the sensors are simply too tiny. Dslrs have much better bokeh because they have bigger sensors. So a FF camera getting more bokeh makes perfect sense to me.

Sep 08, 2010 at 10:27 PM

kakomu
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p.1 #16 · Crop v FF

SamirD wrote:
I think a good way to look at this is to compare to the high-end of the point and shoots. Bokeh is nearly impossible to achieve on these cameras because the sensors are simply too tiny. Dslrs have much better bokeh because they have bigger sensors. So a FF camera getting more bokeh makes perfect sense to me.

It's definitely a factor, but not the sole reason. Also, blurred backgrounds are not impossible to achieve with P&S cameras, but require a lot more effort on the part of the photographer.

Omnicolor wrote:

Very good explanation! Last sentence though,,,,, other way around?

kakomu wrote: It's these factors that account for the increased DoF that you encounter with a full frame camera over a crop camera.

You're right, I'll change it.

Sep 08, 2010 at 10:59 PM

AJSJones
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p.1 #17 · Crop v FF

kakomu wrote:
The problem with most discussions about DoF and camera sensor size is that the variables are NOT controlled very well in the discussion. Most discussions on DoF attempt to either maintain angle of view or framing of a subject. So, between two cameras with different mediums, multiple factors will be adjusted at the same time.
.

The most frequent situation where this comes up is where someone wants take "a picture" with one format or another and wants to know what the effect of that format choice is. The key here being "a picture" - that means the camera position must be the same otherwise it's a different picture with the different format Therefore the focal length must change. Therefore, for a given size print (usually in the mind of the questioner but not overtly stated), the larger format gives shallower DoF - unless,of course, the aperture is closed down to compensate.

PS The part of the image that is out of focus is blurred. The quality of this blur is known as the bokeh - e.g. pleasing, ugly, creamy not "more" or "less".

Sep 08, 2010 at 11:17 PM

kakomu
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p.1 #18 · Crop v FF

AJSJones wrote:
The most frequent situation where this comes up is where someone wants take "a picture" with one format or another and wants to know what the effect of that format choice is. The key here being "a picture" - that means the camera position must be the same otherwise it's a different picture with the different format Therefore the focal length must change. Therefore, for a given size print (usually in the mind of the questioner but not overtly stated), the larger format gives shallower DoF - unless,of course, the aperture is closed down to compensate.

The problem here is that it's NOT the medium that produces a shallower DoF on a full frame camera. If you shorten the focal length of a lens on a crop camera, THAT is the factor that deepens the DoF.

As an example using one of the online DoF calculators, consider the following situation: A full frame camera has a 50mm lens at f/2.8 with a subject 10 feet away. The DoF is about 2.06 feet. Replace the full frame camera with a crop camera and the exact same settings, the DoF is 1.29 feet. Obviously the medium made the DoF shallower. Now, change the focal length to 32mm (approximately the same Angle of view as 50mm on full frame) and the DoF jumps up to 3.25 feet. As you can see, the focal length is the major factor in making the DoF deeper.

If you want to talk about the equivalence of framing and how it affects the picture, that's one thing, but people frequently state that either: A) the larger the format shallower the DoF (it's the other way around, all other things held constant) B) the medium has no affect on DoF (it does).

As I've mentioned before, it's either the distance from the subject or the focal length that play the biggest roles in DoF and background blur.

Sep 08, 2010 at 11:28 PM

AJSJones
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p.1 #19 · Crop v FF

kakomu wrote:
AJSJones wrote:
The most frequent situation where this comes up is where someone wants take "a picture" with one format or another and wants to know what the effect of that format choice is. The key here being "a picture" - that means the camera position must be the same otherwise it's a different picture with the different format Therefore the focal length must change. Therefore, for a given size print (usually in the mind of the questioner but not overtly stated), the larger format gives shallower DoF - unless,of course, the aperture is closed down to compensate.

The problem here is that it's NOT the medium that produces a shallower DoF on a full frame camera. If you shorten the focal length of a lens on a crop camera, THAT is the factor that deepens the DoF.

As I just said - see the highlighted portion. I did not say the medium or the sensor size caused the change in DoF. It was part of a logic train. The focal length change causes the DoF to be different but it's an inescapable consequence of the change in format to get a particular picture.

Sep 08, 2010 at 11:48 PM

kakomu
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p.1 #20 · Crop v FF

AJSJones wrote:
As I just said - see the highlighted portion. I did not say the medium or the sensor size caused the change in DoF. It was part of a logic train. The focal length change causes the DoF to be different but it's an inescapable consequence of the change in format to get a particular picture.

Then, what exactly are you trying to refute from my posts?

Sep 09, 2010 at 12:08 AM

skid00skid00
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p.1 #21 · Crop v FF

You guys need to google Canon's Lenswork book. It explains this in detail. A large part of it is *magnification/needed enlargement* of the sensor/film. The more you enlarge the film/sensor area to the print size, the more depth seems in-focus. The Lenswork book has photos that illustrate this.

Sep 09, 2010 at 12:18 AM

kakomu
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p.1 #22 · Crop v FF

skid00skid00 wrote:
You guys need to google Canon's Lenswork book. It explains this in detail. A large part of it is *magnification/needed enlargement* of the sensor/film. The more you enlarge the film/sensor area to the print size, the more depth seems in-focus. The Lenswork book has photos that illustrate this.

When you say "enlarge the film/sensor area to the print size", are you referring to making the medium larger (e.g. crop to full frame) or are you referring to the magnification needed to go from a medium to a print.

Sep 09, 2010 at 12:22 AM

AJSJones
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p.1 #23 · Crop v FF

kakomu wrote:
AJSJones wrote:
As I just said - see the highlighted portion. I did not say the medium or the sensor size caused the change in DoF. It was part of a logic train. The focal length change causes the DoF to be different but it's an inescapable consequence of the change in format to get a particular picture.

Then, what exactly are you trying to refute from my posts?

I wasn't refuting anything, you were!

gdanmitchell wrote:
Larger formats provide shallower DOF.

kakomu wrote
This isn't true in the least.

I was clarifying the situation in which most people who ask this question find themselves. They want to take a specific picture and have a choice of formats. They are often not concerned with the technical explanations of the dots in the following: If they use a larger format, ... ... ... they get shallower DoF (for a given aperture).

We both understand DoF and the factors controlling it. Someone learning and asking about the issue may want a simple answer for now and not the whole circles and confusion thing (they'll get there sooner or later). If you say to them "technically using a larger format gives you more DoF" - but you don't also say to them "but you won't get the same picture because you didn't change FL" they will be more confused than when they started.

Sep 09, 2010 at 01:09 AM

Mike V
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p.1 #24 · Crop v FF

Also remember when using depth of field calculators and the like, that the depth of field is the part of the image in focus.

It doesn't refer to the background blur.

Sep 09, 2010 at 11:02 AM

ChrisDM
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p.1 #25 · Crop v FF

I have just experienced this with my new 35L, an example to help clarify I hope... The first week with this wonderful lens I was shooting in on vacation with my 5D2, and the background blur was wonderful/dreamy when combined with the relative wide angle. And it being relatively wide I had to move closer to my subject or ask my subject to move closer to me, increasing the effect/decreasing the DOF by decreasing the subject to camera distance or increasing the subject to background distance or both. Then last night I had to use the lens for a work gig on my 1D4 to shoot some indoor action. The 1.3 crop factor is by itself fairly irrelevant when looking strictly at amount of background blur relative to FF, but I had to back up to get the same framing I was experiencing on my 5D2, which changed the distance relationship significantly enough that the dreamy OOF effect of the lens was lessened by this action... So I will be adding a 24L to the lineup, to shoot such scenarios with my 1D4, and hope the effect is similar enough to my 5D2/35L combo.

Sep 09, 2010 at 12:48 PM


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