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10-23-2013, 08:23 PM   #31
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QuoteOriginally posted by traderdrew Quote
I've been playing around with this link:

Online Depth of Field Calculator

For example, when I calculate DOF with the Nikon D7000, I have less DOF than I do with a Nikon FF with the same settings. I thought I have been reading around here that FFs have a narrower DOF. Please explain.
If you're leaving the focal length, aperture, and focusing distance the same then this is what you'd expect. This calculator is assuming that the final print size is the same, so the acceptable circle of confusion on the sensor changes (since the image on the crop sensor is magnified more to get the print than the full frame sensor, we use a smaller acceptable circle of confusion), which affects the DoF (see The DOF equations if you'd like the full gory details).

Where these things pretty much always go wrong is not clearly defining what parameters are staying the same, and what are changing. In the calculator you've linked to, you're changing the framing of the subject if all you change is the format. Usually, when people say "FF has shallower DoF than crop" they're implying that the framing of the subject stays the same in one of two ways:

1) Change the distance to subject to keep the framing of the subject the same. Focal length and aperture remain the same. (this method is for people with a closet of film cameras and lenses)

or

2) Change focal length to keep FoV the same. Distance to subject and aperture stay the same. (this method is for DA lens apologists)

In both situations, the magnification of the subjects image on the Full Frame sensor is higher than on the Crop sensor, and this more than counters the effect of the differing circles of confusion for the two formats (see the simplified equation 13 in the DoF equation link above). Try a few numbers in this calculator:

Similaar DoF and FoV calculator - www.similaar.com

Keep the focal length and aperture constant. Note the Field of View, Height/Width and the DoF. Change the format, but now change the focus distance until the Field of View, Height/Width is the same as before to represent the same framing of your subject (the perspective has changed of course).

Do a similar experiment with changing the focal length so the FoV is the same on the two formats and keep the distance the same so the Field of View, Height/Width is also the same.

10-23-2013, 09:04 PM   #32
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QuoteOriginally posted by stevebrot Quote
Agreed. Having worked with larger formats (up to 4x5), I can tell you without reserve that more DOF is generally better than less.

The one huge exception is with environmental portraits. Images with strongly OOF backgrounds are highly desirable and marketable and are one of the hallmarks of medium format portraiture. Those are hard enough to do with 35mm and almost impossible with APS-C.


Steve
Yea! Environmental portraiture is what interest me.. And that's true.. With APSC, it's quite impossible unless i stand 1,001miles away.. LOL! *exaggerating, i know*

But i guess it all boils down to which aspect of photography interests you. Problem is, it seems that people out there are so "tuned" into acceptance that APSC can almost do everything and FF would be the better one, subjectively.

Let's stop the argument on which is better alright? The whole photography industry just fooled eons of generations into APSC, why? Because it's supposedly cheaper to manufacture as compared to a FF sensor, and therefore the lowered cost will benefit us. But seriously, horses for courses.. If there isn't the specific horse for that specific course, then what? Just race with a pony?

Look at what you're "into" in photography, and then consider the format and calculate the cost.. NEVER settle for less no matter what others say.
10-24-2013, 03:18 AM   #33
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My wife shoots environmental portraiture all the time with a couple of K5s. It isn't that hard -- it is more about composition and positioning your subject relative to the background. The difference in blurring between the formats is the most noticable in wide angles, which aren't the ones that are most frequently used for portraiture anyway.
10-24-2013, 10:35 AM   #34
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QuoteOriginally posted by BrianR Quote
If you're leaving the focal length, aperture, and focusing distance the same then this is what you'd expect. This calculator is assuming that the final print size is the same, so the acceptable circle of confusion on the sensor changes (since the image on the crop sensor is magnified more to get the print than the full frame sensor, we use a smaller acceptable circle of confusion), which affects the DoF (see The DOF equations if you'd like the full gory details).

Where these things pretty much always go wrong is not clearly defining what parameters are staying the same, and what are changing. In the calculator you've linked to, you're changing the framing of the subject if all you change is the format. Usually, when people say "FF has shallower DoF than crop" they're implying that the framing of the subject stays the same in one of two ways:

1) Change the distance to subject to keep the framing of the subject the same. Focal length and aperture remain the same. (this method is for people with a closet of film cameras and lenses)

or

2) Change focal length to keep FoV the same. Distance to subject and aperture stay the same. (this method is for DA lens apologists)

In both situations, the magnification of the subjects image on the Full Frame sensor is higher than on the Crop sensor, and this more than counters the effect of the differing circles of confusion for the two formats (see the simplified equation 13 in the DoF equation link above). Try a few numbers in this calculator:

Similaar DoF and FoV calculator - www.similaar.com

Keep the focal length and aperture constant. Note the Field of View, Height/Width and the DoF. Change the format, but now change the focus distance until the Field of View, Height/Width is the same as before to represent the same framing of your subject (the perspective has changed of course).

Do a similar experiment with changing the focal length so the FoV is the same on the two formats and keep the distance the same so the Field of View, Height/Width is also the same.
If you've done this experiment, maybe you could share a few images. I'm not sure I understand you correctly, but using the same lens, a K-5 gives you more magnification than than a D600, or even a D800, and a D7100 or possibly a K-3 will leave them both in the dust. Maybe I'm just not understanding you correctly.

10-24-2013, 12:02 PM   #35
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Common vernacular

QuoteOriginally posted by stevebrot Quote
Pet peeve of mine, but I hate it when people use the word "stop" to refer to DOF. It truly has no meaning in this context and I am not even sure that statements like the above reliably true. DOF is expressed in units of linear measurement while "stop" is expressed in exposure terms (relative aperture or shutter speed).
When people say 'stop' in this context they simply mean "the DOF change for that same FOV and distance when I stop down one (or open up one) stop."

So for example, shooting a 50mm f/2.8, and you stop down one stop to f/4, your DOF changes one stop, assuming you didn't move closer or farther from the subject.

For a format change, this translates using equivalency to: if you're shooting ~35mm f/2.8 from the same distance on FF, you would have 1.3 less stops of DOF than if you had the same FOV and aperture on aps-c. ie, 35mm f/2.8 aps-c == 50mm f/4.5 FF.

Here's that 1.3 stops DOF difference in pictures - same FOV and aperture on each format:

10-24-2013, 12:20 PM   #36
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Just when I thought I should stop saying "stop" for DOF Jsherman comes in and uses it, hahaha. I think I'll stop using it anyway though as it's not really accurate.

This particular pair of images is the one that sold me on FF. I shoot similar situations and distances alot and could easily see how I'd benefit. I still remember when it was posted the first time in the FF forum, but had a hard time finding it.
10-24-2013, 12:48 PM   #37
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I just think people say things about depth of field and make it sound like it is hard to get narrow depth of field. At longer focal lengths, it is in fact very easy to get narrow depth of field on APS-C. I shoot portraiture mostly at 50-ish mm on APS-C and I get narrow enough depth of field for any purposes. This is a shot of my son shot with DA *55 at f2. Who cares that I could have shot the same portrait with an 85mm at f2.8 on full frame? I don't need more depth of field.


10-24-2013, 01:22 PM   #38
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OK so you need more depth of field. You could say, use one stop more DoF. That would make sense. It's not precise. One stop of DOF changes differently on every lens and is different on every lens. The DoF ƒ5.6 on a 50 mm lens is not the same as the DoF ƒ5.6 on a 30mm lens., used to describe aperture an ƒstop is a measure that's the same on every camera, applies to every lens equally. One is a mushy guestimate kind of thing, the other is a precise measurement. But who cares, you could say it. In jays' example, how would anyone know it would have to be 1 1/3 stop? Long time use with one lens is all that would do it for you. The terminology is just a description of what you're doing. Yesterday shooting with a macro lens and pretty tight DoF I just took pictures at 2.8, 5.6, 11, and 22. I never thought once, I'm changing my DoF two stops, even though that was what I was doing. I thought, I'm closing my Aperture two stops.

The fact that one is a precise term has people using it in a much less precise way in terms of DoF and kind of implying that it has the same accuracy in one situation as it does in it's traditional application. But people just have to realize.. it doesn't.

But really, it's a "let's call the whole thing off" situation.


Last edited by normhead; 10-24-2013 at 01:36 PM.
10-24-2013, 01:34 PM   #39
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I know, just say 2 more or less stops of bokeh. That seems to play right into many people's misunderstanding of what bokeh is.
10-24-2013, 01:37 PM   #40
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QuoteOriginally posted by tuco Quote
I know, just say 2 more or less stops of bokeh. That seems to play right into many people's misunderstanding of what bokeh is.
I hope I never hear anyone say that.
10-24-2013, 03:07 PM   #41
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QuoteOriginally posted by normhead Quote
If you've done this experiment, maybe you could share a few images. I'm not sure I understand you correctly, but using the same lens, a K-5 gives you more magnification than than a D600, or even a D800, and a D7100 or possibly a K-3 will leave them both in the dust. Maybe I'm just not understanding you correctly.
You're using 'magnification' differently than I did. See The DOF equations, the magnification that comes up in the DoF equations is "The image magnification M is defined as the ratio of the image size to the object size." Here, 'Image size' is the size of the projection of the object on the sensor, 'object size' is the measurement of the real life object. If you frame a headshot on an APS-C sensor the same way as on a full frame sensor (including the same body parts of your subject in the picture), the actual image on the full frame sensor is larger and hence it has a larger magnification (imagine if we actually had both formats in film and you could look at the negatives side by side).

I only have full frame in film cameras and have never bothered a comparison. Here are the numbers of an example though, constant aperture and framing of the subject in all cases (the links look the same, but have different numbers entered):

Crop sensor, 50mm, 3m from subject: Similaar DoF and FoV calculator - www.similaar.com
Full Frame sensor, 75mm, 3m from subject: Similaar DoF and FoV calculator - www.similaar.com
Full Frame sensor, 50mm, 2m from subject (note a change of perspective happens): Similaar DoF and FoV calculator - www.similaar.com
10-24-2013, 05:42 PM   #42
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QuoteOriginally posted by Rondec Quote
I just think people say things about depth of field and make it sound like it is hard to get narrow depth of field. At longer focal lengths, it is in fact very easy to get narrow depth of field on APS-C. I shoot portraiture mostly at 50-ish mm on APS-C and I get narrow enough depth of field for any purposes. This is a shot of my son shot with DA *55 at f2. Who cares that I could have shot the same portrait with an 85mm at f2.8 on full frame? I don't need more depth of field.


What you can do with fullframe is shoot 85mm at 1.4 (and pretty cheaply too). With APSC you need to shoot 50mm at f 1.0 to accomplish that. At that setting you get uniform looking background even with busier scenes like the dead trees in Jsherman's shots. This also gives freedom to step back to shoot the whole body instead of head/shouders, and still get blurred backgrounds.

That 24/1.4 that many in this forum seem to want? The cheap, humble, and lightweight 35/2 basically performs the same way in terms of DOF.

A 70-200/2.8 in full frame is like a 50-135/2 APSC zoom.

If shooting at widest aperture for DOF purposes doesn't interest you very much then you're probably better with an APSC, all in all it's lighter and still delivers excellent IQ. This is also why I always champion the DA limiteds. It shows that from day one pentax gets what is great about APSC, and choose to focus on it.

That is until the day Pentax FF comes then the FA lims will finally be able to show their true glory

Last edited by Andi Lo; 10-24-2013 at 06:03 PM.
10-24-2013, 06:22 PM   #43
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QuoteQuote:
You're using 'magnification' differently than I did. See The DOF equations, the magnification that comes up in the DoF equations is "The image magnification M is defined as the ratio of the image size to the object size."
And you can accurately use the DoF equations to predict DoF? I'd like to see your numbers compared to practical results, measured in the field with modern lenses. That might make them meaningful. It must have been done somewhere. I assume since this theory seems to be used endlessly around here, somewhere there are empirical results backing it up.

Edit

OK here's a guy... http://photo.net/learn/optics/dofdigital/.. he seems to include a lot of the things that give me issues, so at least he;s aware that this is far from a simple topic.

QuoteQuote:
For an equivalent field of view, the small-sensor camera has at least 1.6x MORE depth of field than a full-frame camera would have - when the focus distance is significantly less then the hyperfocal distance (but the full-frame format need a lens with 1.6x the focal length to give the same view).

Using the same lens on a small-sensor camera and a full-frame camera, the small-sensor image has 1.6x LESS depth of field than the full-frame image would have (but they would be different images since the field of view would be different)

If you use the same lens on a small-sensor camera and a full-frame camera and crop the full-frame image to give the same view as the digital image, the depth of field is IDENTICAL

If you use the same lens on a small-sensor camera and a full-frame camera, then shoot from different distances so that the view is the same, the small-sensor image will have 1.6x MORE DOF then the film image.

Close to the hyperfocal distance, the small-sensor camera has a much more than 1.6x the DOF of a full-frame camera. The hyperfocal distance of the small-sensor camera is 1.6x less than that of a full-frame camera.
What next has to be calculated in is that, all this assumes the same pixel density. I'd be really interested in seeing what transpires when different pixel sizes are taken into account.

Last edited by normhead; 10-24-2013 at 06:36 PM.
10-24-2013, 06:50 PM   #44
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QuoteOriginally posted by Andi Lo Quote
What you can do with fullframe is shoot 85mm at 1.4 (and pretty cheaply too). With APSC you need to shoot 50mm at f 1.0 to accomplish that. At that setting you get uniform looking background even with busier scenes like the dead trees in Jsherman's shots. This also gives freedom to step back to shoot the whole body instead of head/shouders, and still get blurred backgrounds.

That 24/1.4 that many in this forum seem to want? The cheap, humble, and lightweight 35/2 basically performs the same way in terms of DOF.

A 70-200/2.8 in full frame is like a 50-135/2 APSC zoom.

If shooting at widest aperture for DOF purposes doesn't interest you very much then you're probably better with an APSC, all in all it's lighter and still delivers excellent IQ. This is also why I always champion the DA limiteds. It shows that from day one pentax gets what is great about APSC, and choose to focus on it.

That is until the day Pentax FF comes then the FA lims will finally be able to show their true glory
I just am not someone who pursues narrow depth of field. Honestly, if I am taking a whole body shot (that would be mostly my kids), I usually want to be able to identify the setting, not have it blurred into oblivion. I know that tastes differ, but there is nothing wrong with shooting a portrait and actually having the background be in focus. That sort of shot requires more compositional skill and skill with lighting and so, I am afraid narrow depth of field ends up being the low hanging fruit that photographers lean on.
10-24-2013, 07:24 PM   #45
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QuoteOriginally posted by Rondec Quote
I just am not someone who pursues narrow depth of field. Honestly, if I am taking a whole body shot (that would be mostly my kids), I usually want to be able to identify the setting, not have it blurred into oblivion. I know that tastes differ, but there is nothing wrong with shooting a portrait and actually having the background be in focus. That sort of shot requires more compositional skill and skill with lighting and so, I am afraid narrow depth of field ends up being the low hanging fruit that photographers lean on.
Like I said above if you dont shoot wide open that much, FF wont matter. APSC can do the job in a lighter, smaller package.

However using FF doesnt mean you have to rely on narrow dof. You can always stop down one more stop to achieve what you can get with APSC. Nothing wrong with background being in focus indeed, but what if you want it to be blurred?

The advantage of FF is that you have (at least) two options that you didnt have with APSC 50mm prime: to further thin DOF using an longer lens (85mm/1.4), or to use a zoom lens (28-75 or 70-200).

In my case, the ability to use 28-75/2.8 lens alone is worth going FF, as it replaces three lenses that I use alot: 16-45/4, 35mm/2, 50mm/1.4 (that I always use at f/2). Less lens change means less stress and more keepers

As for it being a low hanging fruit. In weddings and events you might not have a choice of background, so more DOF choices often helps.

Again as with everything in photography, use what works for you. I do still use APSC myself when FF is unecessary.

Last edited by Andi Lo; 10-24-2013 at 07:44 PM.
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