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135mm f2 DC with D700, OR 85mm f1.8D on D3100

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zoomring said:
Lance B said:
zoomring said:
Once again, you are mixing concepts . The OP is correct in using his combination of focal length and sensor size to determine FOV

The follow up up poster and you keep making the incorrect assumption, that the change in DOF was due to the sensor this is 100% wrong. The change of DOF is due to the shorter focal length of 85mm.

Once again, sensor size has no effect on DOF it is strictly determined by focal length+ Fsttop + subject to lens distance, change anyone of these and the DOF changes, period.
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No, you are mixing what I wrote to wriggle out of you mixing up your understanding what I actually said as I never said that the sensor size had anything to do with the DOF
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Perfect! Now you got it!
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I always did have it. It was you that chose not to read it.
zoomring said:
zoomring said:
other than the sensor size of DX requires that he get an 85mm lens and f1.4 rather than a 135mm f2 on FX to get the same FOV.
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A sensor is a inanimate object unable to to force a rational thinking adult into doing anything he or she does not want to do out of his/her own will. It's like the old defense: "the Gun told me to shoot it"
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When did they let you out of the assylum?
zoomring said:
if you as a rational thinking person, decide to switch out the lens then the change of lens causes the change on DOF. The Sensor can not, and will not do that on it's own, therefore it has zero effect on DOF. The change in Focal Length will have direct impact on DOF regardless of what you choose to do, see the difference?
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To get the same FOV on a DX sensor as an FX sensor, from the same position then you need to change to a focal length that is 1.5x shorter on the DX sensor. Therefore the sensor has made you alter the the focal length. Is is what I have said all along and why do you find that so difficult to grasp?

--
Lance B
http://www.pbase.com/lance_b

 
It is correct to note DX has approximately 1 stop more dof for the same viewfinder crop as FX.

The 85mm is a third of stop faster - so the potential dof difference is 0.66 stops.

Photographers styles vary - some would rarely shoot wider than f5.6 - for them the difference is insignificant as they do not use the option :)
For those who regularly take pictures wide open it can be important.

The 135 has the DC function for modifying background detail, or creating an overall soft focus effect. Either is easily done post processing with greater flexibility.
--
Leonard Shepherd

Good photography is mainly about doing simple things well. The challenge is doing simple things well enough for good results.
 
Lance B said:
zoomring wrote:

The follow up up poster and you keep making the incorrect assumption, that the change in DOF was due to the sensor this is wrong. The change of DOF is due to the shorter focal length of 85mm.
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Lance B said:
To get the same FOV on a DX sensor as an FX sensor, from the same position then you need to change to a focal length that is 1.5x shorter on the DX sensor. Therefore the sensor has made you alter the the focal length. Is is what I have said all along and why do you find that so difficult to grasp?
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(this is too easy)

So what happens if the person does not want to change the FOV? he she simply wants to have 2 separate images taken with different sensors, everything else remains the same. What effect does the change in sensor have on DOF?
 
Thanks Andre. I was surprised how sharp this particular copy was @ f2. When shooting @ normal range I find the 135's rendering to be similar to the Zeiss 100 f2 but with an af advantage.

Regards,
Pierre
 
zoomring said:
(this is too easy)

So what happens if the person does not want to change the FOV? he she simply wants to have 2 separate images taken with different sensors, everything else remains the same. What effect does the change in sensor have on DOF?
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No effect. But if you don't care about fov/framing then you have more serious problems than DOF.

If you care about fov and composition then you must alter focal length which in turn will affect the dof. Therefore sensor size affects depth of field. Indirectly , but it does affect.

This discussion is going nowhere. I'm out.
 
pierre1 said:
Thanks Andre. I was surprised how sharp this particular copy was @ f2. When shooting @ normal range I find the 135's rendering to be similar to the Zeiss 100 f2 but with an af advantage.
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Wow, that's sayign something, though judging by your samples, I can see why. I find the AF to be a little unpredictable, but the extra effort to be well worth it.

It can certainly be shap at any paerture when the focus and exposure is nailed properly.

Looking forward to seeing what you do with it.
 
agc1976 said:
zoomring said:
(this is too easy)

So what happens if the person does not want to change the FOV? he she simply wants to have 2 separate images taken with different sensors, everything else remains the same. What effect does the change in sensor have on DOF?
Click to expand...
No effect. But if you don't care about fov/framing then you have more serious problems than DOF.

If you care about fov and composition then you must alter focal length which in turn will affect the dof. Therefore sensor size affects depth of field. Indirectly , but it does affect.

This discussion is going nowhere. I'm out.
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Exactly. This guy is a nit and has no idea about actually taking a photo and why the discussion started in the first place. I've shown him the irrefutable proof, yet he still ignores it.

--
Lance B
http://www.pbase.com/lance_b

 
Lance B said:
agc1976 said:
zoomring said:
(this is too easy)

So what happens if the person does not want to change the FOV? he she simply wants to have 2 separate images taken with different sensors, everything else remains the same. What effect does the change in sensor have on DOF?
Click to expand...
No effect. But if you don't care about fov/framing then you have more serious problems than DOF.

If you care about fov and composition then you must alter focal length which in turn will affect the dof. Therefore sensor size affects depth of field. Indirectly , but it does affect.

This discussion is going nowhere. I'm out.
Click to expand...
Exactly. This guy is a nit and has no idea about actually taking a photo and why the discussion started in the first place. I've shown him the irrefutable proof, yet he still ignores it.
Click to expand...
Now both you guys finally got it, sensor size does not affect DOF. I understand that having to let go of old myths is discomforting, but ultimately understanding the facts, will help your photography in the long run.
 
"When the “same picture” is taken in two different format sizes from the same distance at the same f-number with lenses that give the same angle of view, and the final images (e.g., in prints, or on a projection screen or electronic display) are the same size, the smaller format has greater DOF."
http://en.wikipedia.org/wiki/Depth_of_Field

This is what people mean when they say larger sensor size results in shallower DoF. Moreover, many lenses for 35mm format has such largest aperture (eg f/1.4) that equivalent lenses r not available for the smaller format. For example, u can get 85mm f/1.4 for 35mm, but u will not get 57mm f/0.9 for DX. This is why ppl say that if u want shallower DoF, go with the larger format sensor. And I think this is the most likely use case.
 
zoomring said:
Now both you guys finally got it, sensor size does not affect DOF. I understand that having to let go of old myths is discomforting, but ultimately understanding the facts, will help your photography in the long run.
Click to expand...
You really need to take a step back and challenge your flawed logic. You are wrong.

Constants are required to make valid comparisons. If you wish to ignore constants, then you are not making valid comparisons.
--
Taking pictures of what I want to...
http://www.photobriangray.com/
 
BrianHalcYoN said:
zoomring said:
Now both you guys finally got it, sensor size does not affect DOF. I understand that having to let go of old myths is discomforting, but ultimately understanding the facts, will help your photography in the long run.
Click to expand...
You really need to take a step back and challenge your flawed logic. You are wrong.

Constants are required to make valid comparisons. If you wish to ignore constants, then you are not making valid comparisons.
--
Click to expand...
Correct, the Focal Length, F/stop and subject distance are the constant constant the only variable which changes is the one we are measuring, the sensor . The optical change affected by the sensor is the FOV period.
 
zoomring said:
BrianHalcYoN said:
zoomring said:
Now both you guys finally got it, sensor size does not affect DOF. I understand that having to let go of old myths is discomforting, but ultimately understanding the facts, will help your photography in the long run.
Click to expand...
You really need to take a step back and challenge your flawed logic. You are wrong.

Constants are required to make valid comparisons. If you wish to ignore constants, then you are not making valid comparisons.
--
Click to expand...
Correct, the Focal Length, F/stop and subject distance are the constant constant the only variable which changes is the one we are measuring, the sensor . The optical change affected by the sensor is the FOV period.
Click to expand...
Listen to what you are saying. FoV is changing. If you maintain FoV, DoF changes because focal length HAS TO CHANGE depending on sensor size. What are you trying to convince us? That if you ignore the resulting image, that DoF is the same?
--
Taking pictures of what I want to...
http://www.photobriangray.com/
 
BrianHalcYoN said:
zoomring said:
BrianHalcYoN said:
zoomring said:
Now both you guys finally got it, sensor size does not affect DOF. I understand that having to let go of old myths is discomforting, but ultimately understanding the facts, will help your photography in the long run.
Click to expand...
You really need to take a step back and challenge your flawed logic. You are wrong.

Constants are required to make valid comparisons. If you wish to ignore constants, then you are not making valid comparisons.
--
Click to expand...
Correct, the Focal Length, F/stop and subject distance are the constant constant the only variable which changes is the one we are measuring, the sensor . The optical change affected by the sensor is the FOV period.
Click to expand...
Listen to what you are saying. FoV is changing. If you maintain FoV, DoF changes because focal length HAS TO CHANGE depending on sensor size. What are you trying to convince us? That if you ignore the resulting image, that DoF is the same?
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FOV and DOF are the PRODUCT , not the MANUFACTURER

Your constants are:

-F/Stop
-Focal Length
-Distance
-Sensor

To measure the individual effect of each, you only change one, then measure the results on t he product ( FOV, DOF, Sharpness, Bokeh, Contrast etc)
 
If there is one thing that is the utmost important aspect of a photograph is composition. Therefore, if there is one thing that MUST REMAIN CONSTANT it's composition... NOT focal length.
 
zoomring said:
The statement is incorrect. That statement makes a much more digestible marketing line for consumers, easier to print, pitch and promote. but the facts are that DOF is determined by Focal length+ F/sop and subject to lens distance, I understand it is not a sexy marketing line, but it's the facts.
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I am coming to this party late, but I am not sure what the problem is here. Your statement is exactly correct. DOF is determined by Focal length+ F/sop.

That is why (at the same distance and F-stop) an 85mm lens on a crop sensor will have more DOF then a 135mm lens on a FF sensor. Because all else being equal, an 85mm lens has more DOF then a 135mm lens.

Think of it this way. If you put both lenses on the same camera and took two pictures of the same thing at the same F/stop from the same position. Then if you manually cropped out the parts on the 85mm picture that were not in the 135mm picture, you would end up with more DOF in that picture.

--
http://www.flickr.com/photos/michaelthek/
 
zoomring said:
FOV and DOF are the PRODUCT , not the MANUFACTURER

Your constants are:

-F/Stop
-Focal Length
-Distance
-Sensor

To measure the individual effect of each, you only change one, then measure the results on t he product ( FOV, DOF, Sharpness, Bokeh, Contrast etc).
Click to expand...
Are you interchanging standard focal length, based on mathematics for a 35mm or full frame size, and effective focal length, calculated based on the standard 35mm Focal Length designated by a manufacturer and the sensor's crop factor? Do you understand the difference? Are you assuming that we do not or that we know when you interchange 35mm and crop factor lengths when making your comments?

Let's be clear. Sensor size changes effective focal length of a piece of glass. In this sense, "Focal Length" of a lens is not a constant as crop factor comes into play to maintain a FoV . But if you ignore FoV, you ignore composition which means you have no point. You have to do a much better job of explaining yourself.
--
Taking pictures of what I want to...
http://www.photobriangray.com/
 
BrianHalcYoN said:
zoomring said:
FOV and DOF are the PRODUCT , not the MANUFACTURER

Your constants are:

-F/Stop
-Focal Length
-Distance
-Sensor

To measure the individual effect of each, you only change one, then measure the results on t he product ( FOV, DOF, Sharpness, Bokeh, Contrast etc).
Click to expand...
Are you interchanging standard focal length, based on mathematics for a 35mm or full frame size, and effective focal length, calculated based on the standard 35mm Focal Length designated by a manufacturer and the sensor's crop factor? Do you understand the difference? Are you assuming that we do not or that we know when you interchange 35mm and crop factor lengths when making your comments?
Click to expand...
BrianHalcYoN said:
Let's be clear. Sensor size changes effective focal length of a piece of glass. In this sense, "Focal Length" of a lens is not a constant as crop factor comes into play to maintain a FoV . But if you ignore FoV, you ignore composition which means you have no point. You have to do a much better job of explaining yourself.
Click to expand...
Ready for another dose of reality?... Focal length remains the same regardless of sensor size. :-)

Also, The Imaging circle remains the same size regardless of sensor size:-)

And all the lens optical characteristics remain the same, regardless of sensor size:-)

Sorry to dispel all your marketing myths in one day :-)
 
agc1976 said:
zoomring said:
What you are doing here is measuring the effects of focal length on FOV not measuring the effects of sensor size on DOF . If you want to measure the effects of sensor size on DOF, you need to change change only one variable, you guesses it, the sensor. :-)
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You cannot just conveniently leave FOV out of the equation for the sake of winning an argument :)

Even though FOV it is not directly part of the DOF equation, it directly affects the end result (the photo itself). Different FOV = Different Photograph.

If you want to have THE SAME PHOTOGRAPH with the same fov and same dof you need an aperture approximately 1.3 stops larger if you're using a cropped sensor camera.

Therefore, larger sensor = thinner dof for the same photograph.
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Well said!
 
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