Need a technical explanation for a strange phenomenon/D800E/105mm

[alegator1]

Hi all, I'd appreciate if someone could explain to me the following. I have a D800E and among other lenses I have a Nikon AF-S VR Micro-Nikkor 105mm f/2.8G IF-ED Lens. I mostly shoot in AF mode, VR on, M/A mode. It happens many times that in certain situations when I use the front dial command to set aperture, that I cannot set it down to f2.8 and can only set it above a certain value (for example f3.2 and above), but if I then choose a different subject it will allow me to set it to f2.8. This has happened to me with other lenses too (24-70, 70-200). Is this normal behavior? And if so, what is the explanation? Thanks.

 

[TOF guy]

Nikon AF-S VR Micro-Nikkor 105mm f/2.8G IF-ED Lens. in certain situations when I use the front dial command to set aperture, that I cannot set it down to f2.8 and can only set it above a certain value (for example f3.2 and above), but if I then choose a different subject it will allow me to set it to f2.8. Is this normal behavior? And if so, what is the explanation? Thanks.

Yes this is normal. See this link among others.

 

[alegator1]

Nikon AF-S VR Micro-Nikkor 105mm f/2.8G IF-ED Lens. in certain situations when I use the front dial command to set aperture, that I cannot set it down to f2.8 and can only set it above a certain value (for example f3.2 and above), but if I then choose a different subject it will allow me to set it to f2.8. Is this normal behavior? And if so, what is the explanation? Thanks.

Yes this is normal. See this linkamong others.

 

[GBJ]

Hi alegator1,

I was told by Nikon once that the 105 macro was not a true f2.8 lens.

I read somewhere that at close focus distances, the 105 mm lens cannot operate at f2.8, it changes to something like f3.2. If I then focus 10 ft away for example, then the lens allows me to change the aperture to f 2.8

With regards to your 24-70 and 70-200, I don't believe you would ever have this problem. They are true f2.8 lenses. I have both of them, and I have never not been able to choose f2.8 when I want to.

I may be wrong though, but I'm fairly sure of this.

 

[alegator1]

Hi alegator1,

I was told by Nikon once that the 105 macro was not a true f2.8 lens.

I read somewhere that at close focus distances, the 105 mm lens cannot operate at f2.8, it changes to something like f3.2. If I then focus 10 ft away for example, then the lens allows me to change the aperture to f 2.8

With regards to your 24-70 and 70-200, I don't believe you would ever have this problem. They are true f2.8 lenses. I have both of them, and I have never not been able to choose f2.8 when I want to.

I may be wrong though, but I'm fairly sure of this.

Yes GBJ, that's exactly what I experience with the 105 lens, glad it's not a defect and that it's normal behavior.

I have come across many situations when I was not able to set f2.8 in my 24-70 Nikkor lens (trinity), same behavior as with the 105 lens. I'm almost sure my 24-70 is not defective, rather I think it has to do with the same limitation at certain focal length/aperture/focus distance combinations.

 

[alegator1]

Hi alegator1,

I was told by Nikon once that the 105 macro was not a true f2.8 lens.

I read somewhere that at close focus distances, the 105 mm lens cannot operate at f2.8, it changes to something like f3.2. If I then focus 10 ft away for example, then the lens allows me to change the aperture to f 2.8

Anyway, most of my macro shooting with the 105 lens is at f18 to f22, it produces much sharper images plus the entire subject is in focus due to increased depth of field.

 

[GBJ]

Are you sure F18 - F22 produces sharper images? I understand that that would produce increased depth of field.

 

[alegator1]

Are you sure F18 - F22 produces sharper images? I understand that that would produce increased depth of field.

Well, according to the sharpness chart the optimal values are:

105mm ƒ 2.8G AF-S ED-IF N Micro-Nikkor VR
FX / Film (normal use): F/4.0, F/5.6, F/8.0, F/11.0, and F/16.0
DX (normal use): F/4.0, F/5.6, and F/8.0

but at f18 and higher I get beautiful macro pictures (my subjective perception)

 

[GBJ]

Thanks alegator1,

do you know why the chart has such a wide zone of specified sharpness, as I believe there must be something more going on with that chart, because each lens has a pretty confined variance from a certain F stop that is it's sharpest.

I think there is something to learn here. It's not talking about trying Hyperfocal distance to use a program for combining photos for increased depth of field is it?

 

[alegator1]

In reply to alegator1, 10 min ago

Thanks alegator1,

do you know why the chart has such a wide zone of specified sharpness, as I believe there must be something more going on with that chart, because each lens has a pretty confined variance from a certain F stop that is it's sharpest.

I think there is something to learn here. It's not talking about trying Hyperfocal distance to use a program for combining photos for increased depth of field is it?

You're welcome. AFAIK depth of field and sharpness are two different things. Depth of field increases as the f number increases (aperture decreases). Also, for very high and very low f numbers, diffraction increases hence sharpness decreases. The sweet point depends on each lens, the focal length, number of elements and other factors. As to why this particular lens has a wider range of f values at the sweet spot the answer lies in a field of Physics called Optics.

 

[Robin Casady]

You're welcome. AFAIK depth of field and sharpness are two different things. Depth of field increases as the f number increases (aperture decreases). Also, for very high and very low f numbers, diffraction increases hence sharpness decreases. The sweet point depends on each lens, the focal length, number of elements and other factors. As to why this particular lens has a wider range of f values at the sweet spot the answer lies in a field of Physics called Optics.

Diffraction does not increase at very low f/numbers (wide apertures). The softness at wide apertures comes from other problems such as coma and other lens abberations. Diffraction increases as the effective aperture decreases (f/number gets larger).

Roger of lensrentals.com has a good blog post about the trade-offs between abberations and diffraction.

http://www.lensrentals.com/blog/2013/03/overcoming-my-fentekaphobia

As to the original question about maximum aperture changing, this is something that happens as the lens moves away from the sensor. Put a simple lens on bellows and the farther the lens is from the sensor, the smaller the effective aperture.

It gets more complicated with complex lenses like the 105 Micro-Nikkor, but the practical results are similar.

It is nice that DSLR's can tell you the effective aperture for a given focus distance. In the old days of film one set the aperture ring and had to calculate what the effective aperture was based on magnification.

 

[ShotFromTheSidewalk]

As to the original question about maximum aperture changing, this is something that happens as the lens moves away from the sensor. Put a simple lens on bellows and the farther the lens is from the sensor, the smaller the effective aperture.

It gets more complicated with complex lenses like the 105 Micro-Nikkor, but the practical results are similar.

It is nice that DSLR's can tell you the effective aperture for a given focus distance. In the old days of film one set the aperture ring and had to calculate what the effective aperture was based on magnification.

are u implying that other macro lenses also numerically increase aperture at close focus distances but just don't tell us? that is interesting.

 

[JP Scherrer]

Hi alegator1,

I was told by Nikon once that the 105 macro was not a true f2.8 lens.

I read somewhere that at close focus distances, the 105 mm lens cannot operate at f2.8, it changes to something like f3.2. If I then focus 10 ft away for example, then the lens allows me to change the aperture to f 2.8

With regards to your 24-70 and 70-200, I don't believe you would ever have this problem. They are true f2.8 lenses. I have both of them, and I have never not been able to choose f2.8 when I want to.

I may be wrong though, but I'm fairly sure of this.

This is absolutely normal for most "macro" lens ! The closer you get to the subject, the more the REAL aperture gets smaller !

;-)

J-P.

Photo Galleries at http://www.pbase.com/scherrer
Spherical Panoramas (360x180 degrees) at http://www.360cities.net/profile/jps
Equipment list in profile

 

[JP Scherrer]

Hi alegator1,

I was told by Nikon once that the 105 macro was not a true f2.8 lens.

I read somewhere that at close focus distances, the 105 mm lens cannot operate at f2.8, it changes to something like f3.2. If I then focus 10 ft away for example, then the lens allows me to change the aperture to f 2.8

Anyway, most of my macro shooting with the 105 lens is at f18 to f22, it produces much sharper images plus the entire subject is in focus due to increased depth of field.

Even with "macro" lens, one should avoid opening the aperture beyond about f/13, because diffraction appears and start lowering the IQ of the lens !

;-)

J-P.

Photo Galleries at http://www.pbase.com/scherrer
Spherical Panoramas (360x180 degrees) at http://www.360cities.net/profile/jps
Equipment list in profile

 

[JP Scherrer]

As to the original question about maximum aperture changing, this is something that happens as the lens moves away from the sensor. Put a simple lens on bellows and the farther the lens is from the sensor, the smaller the effective aperture.

It gets more complicated with complex lenses like the 105 Micro-Nikkor, but the practical results are similar.

It is nice that DSLR's can tell you the effective aperture for a given focus distance. In the old days of film one set the aperture ring and had to calculate what the effective aperture was based on magnification.

are u implying that other macro lenses also numerically increase aperture at close focus distances but just don't tell us? that is interesting.

Indeed, most "macro" lens have this "problem !

....but in REAL LIFE, this should not interfere, as a macro lens is not intended to be used at full aperture !

;-)

J-P.

Photo Galleries at http://www.pbase.com/scherrer
Spherical Panoramas (360x180 degrees) at http://www.360cities.net/profile/jps
Equipment list in profile

 

[sshoihet]

As to the original question about maximum aperture changing, this is something that happens as the lens moves away from the sensor. Put a simple lens on bellows and the farther the lens is from the sensor, the smaller the effective aperture.

It gets more complicated with complex lenses like the 105 Micro-Nikkor, but the practical results are similar.

It is nice that DSLR's can tell you the effective aperture for a given focus distance. In the old days of film one set the aperture ring and had to calculate what the effective aperture was based on magnification.

are u implying that other macro lenses also numerically increase aperture at close focus distances but just don't tell us? that is interesting.

--

The focal length and f-number of a lens are calculated at infinity. If the focal length increases for focusing at very close distances, that increases the f-number as N=f/D

 

[Robin Casady]

As to the original question about maximum aperture changing, this is something that happens as the lens moves away from the sensor. Put a simple lens on bellows and the farther the lens is from the sensor, the smaller the effective aperture.

It gets more complicated with complex lenses like the 105 Micro-Nikkor, but the practical results are similar.

It is nice that DSLR's can tell you the effective aperture for a given focus distance. In the old days of film one set the aperture ring and had to calculate what the effective aperture was based on magnification.

are u implying that other macro lenses also numerically increase aperture at close focus distances but just don't tell us? that is interesting.

What do you mean by "numerically"? I'm saying that as the distance between sensor and lens increases, the effective aperture gets smaller. This setup uses an EL Nikkor f/5.6 enlarging lens. The D800E PDAF is supposed to work at f/8 and wider. At a certain distance the AF does work. As you move the lens closer to the subject you have to move the camera body farther away from the lens to achieve focus. As you do this there is a point where the AF fails because the effective aperture has become smaller than f/8. However, the aperture ring on the lens remains at f/5.6.

Since this lens is not electronically connected to the camera, the camera does not report the effective aperture as it does with the 105mm Micro-Nikkor.

--
Robin Casady
http://www.robincasady.com/Photo/index.html
"Get your facts first, then you can distort them as you please."
—Mark Twain

 

[alegator1]

Hi alegator1,

I was told by Nikon once that the 105 macro was not a true f2.8 lens.

I read somewhere that at close focus distances, the 105 mm lens cannot operate at f2.8, it changes to something like f3.2. If I then focus 10 ft away for example, then the lens allows me to change the aperture to f 2.8

Anyway, most of my macro shooting with the 105 lens is at f18 to f22, it produces much sharper images plus the entire subject is in focus due to increased depth of field.

Even with "macro" lens, one should avoid opening the aperture beyond about f/13, because diffraction appears and start lowering the IQ of the lens !

;-)

J-P.

Photo Galleries at http://www.pbase.com/scherrer
Spherical Panoramas (360x180 degrees) at http://www.360cities.net/profile/jps
Equipment list in profile

Yes I know, but who knows why, with the 105 I get crisp pictures at f22

 

[alegator1]

As to the original question about maximum aperture changing, this is something that happens as the lens moves away from the sensor. Put a simple lens on bellows and the farther the lens is from the sensor, the smaller the effective aperture.

It gets more complicated with complex lenses like the 105 Micro-Nikkor, but the practical results are similar.

It is nice that DSLR's can tell you the effective aperture for a given focus distance. In the old days of film one set the aperture ring and had to calculate what the effective aperture was based on magnification.

are u implying that other macro lenses also numerically increase aperture at close focus distances but just don't tell us? that is interesting.

--

The focal length and f-number of a lens are calculated at infinity. If the focal length increases for focusing at very close distances, that increases the f-number as N=f/D

What is "N" and "D" in your formula N=f/D? I assume f=f-number (2.8, etc) or is it focal length?

 

[alegator1]

a macro lens is not intended to be used at full aperture !
;-)

J-P.

Photo Galleries at http://www.pbase.com/scherrer
Spherical Panoramas (360x180 degrees) at http://www.360cities.net/profile/jps
Equipment list in profile

So then why is this 105 macro lens designed with f2.8? To make it multipurpose for non macro shots too?