Diff. in use of Z 105 vs old F 105

[powerbook]

Hi,


For an friend I have to ask the following, as I am not near him and have therefore not experienced himself what he asks about.

He has a Z50 camera with FTZ-2 and a Nikon AF-S VR Micro-Nikkor 105mm f/2.8G IF-ED and a Tamron 60mm macro lens.

Both optics behave similarly in terms of shutter speeds, aperture and ISO etc. But now he bought a NIKKOR Z MC 105mm f/2.8 VR S which behaves completely different.

The Z105 lets in much more light, so with the same shutter speed and aperture you get a much lower ISO etc. It's so much better that he actually wonders about it.

If I compare my own F lens 70-200F2.8 and the Z lens 28-200F4-6.3 at 200mm and same aperture and shutter speed, I don't think I have any difference in light and ISO.

Is this normal?

Thanks ;-)

 

[Laqup]

He is probably confused. Ask him to provide you with two test shots for comparison. (Including exif)

Small differences are to be expected but not on the scale you hint at.

 

[rwol1970]

Equipments errors seem not logical since the AF-S and Tamron behave the same. So this could only be a human error. It would be different if the Z had less light. In that case there could be a technical issue with the Z lens.

 

[BasilG]

Both optics behave similarly in terms of shutter speeds, aperture and ISO etc. But now he bought a NIKKOR Z MC 105mm f/2.8 VR S which behaves completely different.

The Z105 lets in much more light, so with the same shutter speed and aperture you get a much lower ISO etc. It's so much better that he actually wonders about it.

He's confused.

 

[Nikonlinks]

F-stop is a mathematical ratio of lens element diameter to focal length It is a rough barometer of light transmission but not exactly. You will often see a half stop variation among different lens models of the same f-stop. This was particularly a problem for us old guys before through the lens metering. We had to measure light with a separate meter and transfer settings to the camera. What worked well with one lens was not the same with another due to variance in light transmission. Remember we didn’t have a digital screen to chimp, results not seen till after processing, and every push of the button cost $1!

Light transmission is measured in T-stops. One lens of same focal length versus another of the same T-stop should be very close to the same.

 

[J2daV]

Could the old one have lens fungus or something on the glass that makes it darker? If they are in new condition, they should be the same in terms of light transmission. But things happen in the life of a lens.

 

[Leonard Shepherd]

Hi,

The Z105 lets in much more light, so with the same shutter speed and aperture you get a much lower ISO etc.

Very Minor differences possible

Significant differences are not possible PROVIDED one lens is not being compared at one-to-one focus and the other is at infinity.

As an example either lens changes from a readout of f2 .8 at infinity to about f4 .5 at 1 to 1 focus.

Sometimes the exposure read out difference between infinity and 1:1 focus with most Nikon macro lenses can lead to some misunderstanding

 

[Satyaa]

Obviously, we are guessing because we haven't seen the situation in person. And the big assumption here is that everything else has remained the same in terms of the subject, lighting, distance, etc., etc.

I have two guesses.

One is that the lighting has changed (especially if it is outdoors). A variation of this could be that lighting in a part of the scene has changed enough that the camera is metering differently.

Second is that the difference is not that big. For example, ISO 6400 to 5000 may seem like a big number, but it is less than half-stop. It's not as big a difference as ISO 100 to 400 (two full stops).

This doesn't sound like a showstopper, but I am curious what you end up finding out.

All the best.

 

[powerbook]

Obviously, we are guessing because we haven't seen the situation in person. And the big assumption here is that everything else has remained the same in terms of the subject, lighting, distance, etc., etc.

I have two guesses.

One is that the lighting has changed (especially if it is outdoors). A variation of this could be that lighting in a part of the scene has changed enough that the camera is metering differently.

Second is that the difference is not that big. For example, ISO 6400 to 5000 may seem like a big number, but it is less than half-stop. It's not as big a difference as ISO 100 to 400 (two full stops).

This doesn't sound like a showstopper, but I am curious what you end up finding out.

All the best.

He has since sold his old 105 and his Tamron and his FTZII, but it is quite clear he says that the new Z 105 seems to let in more light. He's been shooting insects with the old 105 for a long time so he knows what he's talking about.

I was just wondering myself if there might be something to the new Z lenses letting in more light, since Nikon writes everywhere about Z lenses, "More light".

I agree that it shouldn't be that obvious a difference at all.

 

[BasilG]

Obviously, we are guessing because we haven't seen the situation in person. And the big assumption here is that everything else has remained the same in terms of the subject, lighting, distance, etc., etc.

I have two guesses.

One is that the lighting has changed (especially if it is outdoors). A variation of this could be that lighting in a part of the scene has changed enough that the camera is metering differently.

Second is that the difference is not that big. For example, ISO 6400 to 5000 may seem like a big number, but it is less than half-stop. It's not as big a difference as ISO 100 to 400 (two full stops).

This doesn't sound like a showstopper, but I am curious what you end up finding out.

All the best.

He has since sold his old 105 and his Tamron and his FTZII, but it is quite clear he says that the new Z 105 seems to let in more light. He's been shooting insects with the old 105 for a long time so he knows what he's talking about.

I was just wondering myself if there might be something to the new Z lenses letting in more light, since Nikon writes everywhere about Z lenses, "More light".

No.

 

[Leonard Shepherd]

I was just wondering myself if there might be something to the new Z lenses letting in more light, since Nikon writes everywhere about Z lenses, "More light".

Only Nikon can answer why they write about "More light".

I agree that it shouldn't be that obvious a difference at all.

f2 .8 is f2 .8.

Light actually transmitted can vary slightly between lenses due to different glass absorption and the coatings. The reduction is sometimes referred to as a T stop.

The T stop difference compared to 100% light transmission is often around a quarter to half a stop.

--
Leonard Shepherd
In lots of ways good photography is similar to learning to play a piano - it takes some practice to develop some skill.

 

[iljitsch]

f2 .8 is f2 .8.

You would think that. But at very short distances, the same aperture will let in less light. The reviews of the Z 105 macro indicate that the display compensates for that. So a close shot wide open will not be f/2.8 at 1:1, but f/4.8 instead.

Now suppose you set the aperture to f/8. So that means the aperture is closed 1.5 stops.

On a lens that doesn't support this adjustment in the f number display, if you set the aperture to f/8 it will close the aperture 3 stops.

So both lenses at "f/8" but one will show an image that is 1.5 stops brighter than the other.

I am unsure if the AF-S version of the 105 mm macro also supports the adjustment. My old manual focus version of this lens definitely doesn't.

 

[BasilG]

f2 .8 is f2 .8.

You would think that. But at very short distances, the same aperture will let in less light. The reviews of the Z 105 macro indicate that the display compensates for that. So a close shot wide open will not be f/2.8 at 1:1, but f/4.8 instead.

True.

Now suppose you set the aperture to f/8. So that means the aperture is closed 1.5 stops.

On a lens that doesn't support this adjustment in the f number display, if you set the aperture to f/8 it will close the aperture 3 stops.

So both lenses at "f/8" but one will show an image that is 1.5 stops brighter than the other.

Are you saying that if you set f/8 at infinity and focus closer, the aperture readying stays at f/8? Or just that if you are already at 1:1 and set f/8, it is f/8 at that focus distance (but then if you were to focus at infinity, it would show something else)?

I am unsure if the AF-S version of the 105 mm macro also supports the adjustment.

Yes. The the AF-S shows the corrected f-stop. I think even the older AF-D did.

 

[bobn2]

Obviously, we are guessing because we haven't seen the situation in person. And the big assumption here is that everything else has remained the same in terms of the subject, lighting, distance, etc., etc.

I have two guesses.

One is that the lighting has changed (especially if it is outdoors). A variation of this could be that lighting in a part of the scene has changed enough that the camera is metering differently.

Second is that the difference is not that big. For example, ISO 6400 to 5000 may seem like a big number, but it is less than half-stop. It's not as big a difference as ISO 100 to 400 (two full stops).

This doesn't sound like a showstopper, but I am curious what you end up finding out.

All the best.

He has since sold his old 105 and his Tamron and his FTZII, but it is quite clear he says that the new Z 105 seems to let in more light. He's been shooting insects with the old 105 for a long time so he knows what he's talking about.

I was just wondering myself if there might be something to the new Z lenses letting in more light, since Nikon writes everywhere about Z lenses, "More light".

I agree that it shouldn't be that obvious a difference at all.

The key might be in the subject matter. What's really important is a factor called 'numerical aperture' or NA. Nowadays f-number is defined in terms of the NA, not as it was in old days as the ratio between focal length and aperture. At infinity focus the old f-number and new f-number are the same, but when focussing close the old-style f-number (called 'effective f-number' in macro work) increases, whilst the new-style one stays the same. The new style one is an ISO standard, so should be being used. My guess is that the Z camera's aperture system is calibrated according to the ISO standard, whilst the F mount system wasn't, for compatibility with old F-mount lenses. This would result in what your friend observes, at the same f-number setting the Z lens would let in more light than the F-mount lenses.

Often macro workers haven't had to bother with the macro correction factor, because TTL metering compensates automatically, so they forget that it was there.

--
Is it always wrong
for one to have the hots for
Comrade Kim Yo Jong?

 

[Leonard Shepherd]

at very short distances, the same aperture will let in less light. The reviews of the Z 105 macro indicate that the display compensates for that. So a close shot wide open will not be f/2.8 at 1:1, but f/4.8 instead.

Not exactly - the reasons are complicated.

Historically lenses lost the equivalent of 2 stops of light by 1:1 - and the viewfinder was 2 stops darker. Before the advent of TTL significant exposure adjustments were required.

With these "traditional" lenses the effective focal length of lens increases the closer you focus and the size of the aperture does not change.

Staying with traditional lenses the increase in focal length is the equivalent of using a smaller aperture and the unchanged aperture size is the equivalent of a higher aperture number. The increase in focal length offsets the smaller aperture for depth of field. With a "traditional" lens there is no need to make any depth of field adjustment compared to a traditional depth of field table.

More recently most macro lenses (and some others) "breathe" significantly - shortening focal length/widening angle of view without changing the size of the aperture as you focus closer - to in effect a wider aperture with less depth of field. The wider aperture results in less depth of field than in a traditionally calculated depth of field table (see note 1).

HOWEVER - current Nikon macro lenses open up the aperture size compared to infinity in close up photography. There is then a brighter viewfinder - offset by reduced depth of field. The aperture size change can be easily observed on a DSLR looking through the front of a macro lens stopped down by pressing depth of field preview and noting the change in aperture size between infinity and 1:1 focus distance (see note 2).

This combined effect of shortening angle of view and physically opening up the aperture result in the same camera exposure at 1:1 as at infinity - contradicting historical macro exposure guidance

The depth of field you get is somewhere between the f2.8 and f4.8/5.6 (lens dependent) as the combined effect of widening the angle of view and separately opening up the aperture do not exactly cancel each other out.

About 1 stop less depth of field than on your f4.8 read-out is a reasonable average at 1:1.

Note 1 - getting technical - for accurate depth of field in close up the "P" (pupillary exit) factor - which can be approximately calculated by viewing the size of the aperture from the front and the back - should be included in depth of field formula.

Note 2 - the shrewd may query what happens if the lens is at f2.8 at infinity - and cannot be opened up wider than f2.8 at 1:1. The answer is DSLR's increase the exposure time instead.

Back to the original post - 2 lenses which operate in the same way were being compared - meaning the exposures should be very similar.

-
Leonard Shepherd
In lots of ways good photography is similar to learning to play a piano - it takes some practice to develop some skill.

 

[iljitsch]

Are you saying that if you set f/8 at infinity and focus closer, the aperture readying stays at f/8? Or just that if you are already at 1:1 and set f/8, it is f/8 at that focus distance (but then if you were to focus at infinity, it would show something else)?

I wasn't making any claims in this regard, but let me do that now:

Extrapolating from what I've seen in reviews, if you were to set the Z MC 105 to f/4 while focused at infinity, and then start focusing closer, first the aperture should (physically) open up while the camera keeps displaying f/4. But at 1:1 wide open is f/4.5 with this lens, so when you reach 1:1, the aperture the camera displays should be f/4.5.

And if you take two shots at f/8, one focused to infinity and one to 1:1, you should get the same shutter time and the same exposure. But if you break out your calipers, you'd see that at 1:1 the aperture is opened much wider. I assume 1 1/3 stops, based on f/4.5 minimum aperture at 1:1 and f/2.8 at infinity.

 

[iljitsch]

With these "traditional" lenses the effective focal length of lens increases the closer you focus and the size of the aperture does not change.

Yes, easy to observe as you turn the focus ring and the entire lens extends. Of course modern lenses don't do that anymore.

More recently most macro lenses (and some others) "breathe" significantly - shortening focal length/widening angle of view without changing the size of the aperture as you focus closer

Well, first of all that seems unhelpful for a macro lens :-O and second, in a review of the Z MC 105, the reviewer showed the opposite: the field of view gets smaller (the subject takes up a larger part of the frame) as you focus more closely. And the reviewer said that he hadn't seen a macro lens that doesn't do this. (Although another reviewer said a 180 mm macro lens doesn't breathe.)

 

[just Tony]

f2 .8 is f2 .8.

You would think that. But at very short distances, the same aperture will let in less light.

That’s because the lens isn’t at f/2.8 any more, it truly did change due to the focusing extension as you indicated below. There is no mystery; f/2.8 is f/2.8, and f/4.8 is f/4.8. The discrepancy between f stop and T stop that is due to the efficiency losses by reflection and absorption is still in effect at any focus extension.

The reviews of the Z 105 macro indicate that the display compensates for that.

It’s merely reporting the truth about the changed optical reality, it’s not an adjusted report. The image really did get dimmer.

So a close shot wide open will not be f/2.8 at 1:1, but f/4.8 instead.

Now suppose you set the aperture to f/8. So that means the aperture is closed 1.5 stops.

On a lens that doesn't support this adjustment in the f number display, if you set the aperture to f/8 it will close the aperture 3 stops.

The higher-featured lens will adjust the iris during focusing such that it really will stay at a real f/8. As you rack the focus from infinity to the close limit the iris blades physically open up wider in order to maintain a constant and true f/8. That is an intervention via firmware. The iris won’t reach its physical limit when you rack all the way in close. It will remain at a true f/8 at all distances.

Similarly, variable aperture zooms are able to maintain a constant aperture during zooming if they had been stopped down enough. That’s a firmware feature that overrides the native optical behavior. Nikon has decided to hold the actual resulting aperture constant wherever that is physically possible in order to present a simplified behavior as much as possible. If the iris dies happen to reach its limit because it wasn’t stopped down or stopped down just a little then the firmware will be unable to continue to hold the aperture constant.

So both lenses at "f/8" but one will show an image that is 1.5 stops brighter than the other.

I am unsure if the AF-S version of the 105 mm macro also supports the adjustment.

They do.

My old manual focus version of this lens definitely doesn't.

No, we had to use tables to help us compensate for the real f-stop at times that it changed due to extension, IF we were using an external meter or manual flash. TTL metering on the other hand handles the dimmer image automatically. That was an advertising selling point when TTL was introduced. The painted markings on the aperture ring have no way to adjust to the new reality which can give the false impression that the aperture was constant.

 

[bobn2]

Similarly, variable aperture zooms are able to maintain a constant aperture during zooming if they had been stopped down enough.

At this point it's worthwhile pointing out a terminological inexactitude. 'Constant aperture zooms' aren't constant aperture, they are constant f-number. The aperture has to change as the lens is zoomed to keep the f-number the same, which might be done optically or mechanically or a mixture of both. Some 'variable aperture zooms' are actually 'constant aperture zooms', but since the aperture remains the same and the focal length changes, they are variable f-number zooms.

 

[Leonard Shepherd]

LMore recently most macro lenses (and some others) "breathe" significantly - shortening focal length/widening angle of view without changing the size of the aperture as you focus closer

Well, first of all that seems unhelpful for a macro lens :-O and second, in a review of the Z MC 105, the reviewer showed the opposite: the field of view gets smaller (the subject takes up a larger part of the frame) as you focus more closely. And the reviewer said that he hadn't seen a macro lens that doesn't do this. (Although another reviewer said a 180 mm macro lens doesn't breathe.)

There are 2 things going on.

First ignoring breathing the angle of view a traditional f2.8 105mm at infinity changes to an angle of view of 210mm f5.6 by 1:1 - with the subject taking a larger part of the frame i.e. with increased subject magnification.

Second the focus breathing on current Nikon 105mm lenses brings in an element of a wider angle of view; reducing the magnification effect that would occur with a lens from decades ago that does not focus breathe.

As an example if the AF 105 macro D f2.8 did not breathe it would have the magnification of a 210 mm and an exposure equivalent to f5.6 at 1:1.

It does breathe to 78.5 mm compared to the infinity angle of view; equivalent to 157mm at 1:1.

Provided it is not used wide open a combination of focus breathing and physically opening up the aperture relative to the infinity focus aperture size eliminates the 2 stops loss of light compared to an infinity focus meter reading.

If you wish, with the camera on a tripod, using depth of field preview at perhaps f11 (needs a custom setting in the menus with ML) and focus peaking; a good idea of the actual depth of field can be obtained.

Outside of technical debate it perhaps matters little that when a current Nikon macro lens at 1:1 indicates f4.8/5.6 the depth field is around a stop less than that indicated using a conventional depth of field table; and you get an infinity meter reading instead of a meter reading for 2 stops darker.