Does flange distance impact sharpness?

[sid_19911991]

I recently asked the folks running Greys of Westminster YouTube channel via live chat about why the Z lenses are significantly sharper than f mount glass.

They implied that the larger Z mount with the 16 mm flange distance as opposed to the 46 mm flange distance on the f mount is a big reason for it. Also, that Nikon can construct & design similar focal length lenses better to get more sharpness.

I want to know if all things being identical or very similar, will the 500pf be sharper on say a Z7 compared with its performance on the D850?

I know Z7 has the advantage of auto lens calibration & IBIS...


Also, does flange distance make an impact?
What do you think folks?

 

[NorthernFocus]

More than the flange design the hybrid AF should result in optimum lens performance. As far as the flange design the increased diameter is more beneficial than the difference in flange to sensor distance. The less the light has to bend the better.

 

[DRwyoming]

I want to know if all things being identical or very similar, will the 500pf be sharper on say a Z7 compared with its performance on the D850?

Perhaps if Nikon releases a Z mount version of the 500mm PF, but if you use the F mount 500mm PF the flange distance doesn't change because of the spacing provided by the FTZ adapter. The FTZ adapter's main purpose is to hold F mount lenses at the same distance from the sensor as they would be on a DSLR when you account for the missing mirror box assembly. IOW, an F mount lens on a Z mount body via the FTZ adapter maintains the same effective flange distance the F mount lens was designed to support.

 

[sid_19911991]

Perhaps if Nikon releases a Z mount version of the 500mm PF, but if you use the F mount 500mm PF the flange distance doesn't change because of the spacing provided by the FTZ adapter. The FTZ adapter's main purpose is to hold F mount lenses at the same distance from the sensor as they would be on a DSLR when you account for the missing mirror box assembly. IOW, an F mount lens on a Z mount body via the FTZ adapter maintains the same effective flange distance the F mount lens was designed to support.

Hmmm, oh yeah, totally forgot about the FTZ.

 

[fcotterill]

The 16mm throat aka Flange distance is about the minimum possible to still be able to fit rear lens elements close to the shutter and sensor assembly. Any closer would risk damage etc. The 55mm wide diameter Z mount allows a much wider 110 degree diagonal for optimal light capture across the sensor (less vignetting, distortions etc) in optical designs. Compare much narrower F mount which is much further away from sensor plane (accommodating the mirror mechanisms et al).

I have yet to read firm statements or comparative tests but these benefits presumably improve light transmission and minimize distortion etc with the new Z-TCs as this Z mount architecture makes it much less challenging to design fast and also high quality optics. This applies especially to shorter focal lengths. The wide 55mm diameter mount also makes IBIS simpler as it projects outside the sensor diagonal. [EDIT: Theoretically a f0.6 Lens is possible to desighn on the Z Mount - see this interview
https://www.nikon-image.com/sp/z9_specialinterview/02_zmount/

This video by Nikon engineer explains this far better than I'm able And also in this interview, particularly pertaining to video, a market into which Nikon continues to see great significance for its Z System

Nikon au CP+ 2019 : « La beauté de la monture Z est de pouvoir guider la lumière de manière très naturelle »

Au CP+ 2019, nous avons rencontré deux ingénieurs de chez Nikon : Kazuharu Imafuji et Satoshi Yamazaki. Nous avons pu revenir avec eux sur la monture Z annoncée en 2018, les avantages qu’elle procure et parler également de vidéo, un domaine où Nikon souhaite faire sa place.

phototrend.fr

And a more recent Graphical Explanation in this video

So do the detailed explanations in this dpr thread with inputs from Jim Kasson and others who grasp the deeper technical concepts and factors

These diagrams alone is worth many words :

You can only see EXIF info for this image if you are logged in.

E- vs L- vs RF- vs Z-mount: Nikon Z Mirrorless Talk Forum: Digital Photography Review

Expert news, reviews and videos of the latest digital cameras, lenses, accessories, and phones. Get answers to your questions in our photography forums.

www.dpreview.com

 

[ElenaH]

I see, that we are talking more about sharpness than about resolution (lines per inch or mm). The less resolving lens can provide a sharp image as well. What do we need sharpness or resolution?
I think, that Z-design (52mm opening and 16mm flange distance) gives the opportunity to design good lenses in easier way (perhaps). Maybe, that is what the guys meant.
I don't think, that the camera design means the better sharpness. It is always the lens.
For example, some Zeiss lenses are better in resolution than Nikon lenses. I have tested on ISO charts with Z7. So, to be precise, Zeiss Milvus 135mm/2 has more resolution (details, lines per inch) than Nikon S 70-200/2, for example. It is possible that Zeiss will be also better than some Z-primes.
The sensor is also important. Something must catch what the lens can resolve! ;-) So, the more MP will give more resolution with the same (excellent) lens.

 

[sid_19911991]

The 16mm throat aka Flange distance is about the minimum possible to still be able to fit rear lens elements close to the shutter and sensor assembly. Any closer would risk damage etc. The 55mm wide diameter Z mount allows a much wider 110 degree diagonal for optimal light capture across the sensor (less vignetting, distortions etc) in optical designs. Compare much narrower F mount which is much further away from sensor plane (accommodating the mirror mechanisms et al).

I have yet to read firm statements or comparative tests but these benefits presumable improve light transmission and minimize distortion etc with the new Z-TCs as this Z mount architecture makes it much less challenging to design fast and also high quality optics. This applies especially to shorter focal lengths. The wide 55mm diameter mount also makes IBIS simpler as it projects outside the sensor diagonal.

This video by Nikon engineer explains this far better than I'm able

So do the detailed explanations in this dpr thread with inputs from Jim Kasson and others who grasp the deeper technical concepts and factors

These diagrams alone is worth many words :

View attachment 27822

E- vs L- vs RF- vs Z-mount: Nikon Z Mirrorless Talk Forum: Digital Photography Review

Expert news, reviews and videos of the latest digital cameras, lenses, accessories, and phones. Get answers to your questions in our photography forums.

www.dpreview.com

View attachment 27821

That's an excellent share. Will have a read. Thanks.

 

[sid_19911991]

I see, that we are talking more about sharpness than about resolution (lines per inch or mm). The less resolving lens can provide a sharp image as well. What do we need sharpness or resolution?
I think, that Z-design (52mm opening and 16mm flange distance) gives the opportunity to design good lenses in easier way (perhaps). Maybe, that is what the guys meant.
I don't think, that the camera design means the better sharpness. It is always the lens.
For example, some Zeiss lenses are better in resolution than Nikon lenses. I have tested on ISO charts with Z7. So, to be precise, Zeiss Milvus 135mm/2 has more resolution (details, lines per inch) than Nikon S 70-200/2, for example. It is possible that Zeiss will be also better than some Z-primes.
The sensor is also important. Something must catch what the lens can resolve! ;-) So, the more MP will give more resolution with the same (excellent) lens.

Not familiar with the technical meaning of resolution, sharpness etc.

I guess I meant resolution as well.

I have causally noticed (not sure if I am correct) far more details when the 500pf is paired with the D850 (even when cropped by 1.5x) as opposed to a D500, although the effective slightly megapixels are more on the D500!

Does that make sense?

Do you any clue as to what perceptual megapixels are as recorded in DXO Mark website.

 

[ElenaH]

have causally noticed (not sure if I am correct) far more details when the 500pf is paired with the D850

it is interesting but D500 has an older sensor. D850 has newer backlit sensor which differ for example also in dynamic range (much bette than old in D500)
What is also important: when we test then we need to test under the same circumstances with the lowest native ISO. The higher the ISO the less details. Interestingly, even less color - test it! This is why landscape photographers always use tripod: to get the lowest ISO and the better colours (beside the sharpness or resolution)
When you had a bit higher ISO on D500 then yes, combined with old sensor it will deliver less details with the same lens.

 

[sid_19911991]

it is interesting but D500 has an older sensor. D850 has newer backlit sensor which differ for example also in dynamic range (much bette than old in D500)
What is also important: when we test then we need to test under the same circumstances with the lowest native ISO. The higher the ISO the less details. Interestingly, even less color - test it! This is why landscape photographers always use tripod: to get the lowest ISO and the better colours (beside the sharpness or resolution)
When you had a bit higher ISO on D500 then yes, combined with old sensor it will deliver less details with the same lens.

Yes, higher ISO causes a loss in sharpness.

Yes no two set ups can be identcial.

I personally like to know which set up is better rather than conducting a test that won't have much of a practical value.

I find a lot of pro photographers doing tests for YouTube not mirrorring practical use.

For example, taking photos of letters or markings at about 50 feet at an ISO of 100.

Such a test would give comparable results to a D850/500 f4 combo even with D500/200-500 combo! Like the center sharpness in this case won't be too different. One can then make a bulletproof conclusion that the 200-500 is almost as sharp as 500 f4.

But we all know that such a test is misleading.

Hence, I feel practical tests with slight differences/variables hold more value as they mirror actual use & outcome.

 

[ElenaH]

@sid_19911991 you are right, the practical tests are more important becasue we don't take pictures of ISO charts ;-) !
I do the practical tests (for example, that Zeiss against Nikkor and Tamron on landscape) and sometimes I really surprised to see no difference between native and third-party lens...
Regarding Z-cameras. The results will look better in Lightroom (LR) becasue LR has pre-defined profiles for Z. Look at the sharpening and noise reduction right after importing pictures in LR. It is already set for you. Or pre-set. Did you know that?
But it is not set for D850.
Do you use LR?
Beside the software with pre-set options the firmware can also play some role. With each new firmware we upload the lens information to the camera and corrections can be done alerady in the camera itself.

 

[sid_19911991]

@sid_19911991 you are right, the practical tests are more important becasue we don't take pictures of ISO charts ;-) !
I do the practical tests (for example, that Zeiss against Nikkor and Tamron on landscape) and sometimes I really surprised to see no difference between native and third-party lens...
Regarding Z-cameras. The results will look better in Lightroom (LR) becasue LR has pre-defined profiles for Z. Look at the sharpening and noise reduction right after importing pictures in LR. It is already set for you. Or pre-set. Did you know that?
But it is not set for D850.
Do you use LR?
Beside the software with pre-set options the firmware can also play some role. With each new firmware we upload the lens information to the camera and corrections can be done alerady in the camera itself.

I didn't mean you, but yeah good to know that you do the more practical tests.

No I don't use LR.

From what a few pro photographers have suggested including the likes of Matt Irwin & Thomas Vijayen (Nikon Ambassador), Nikon's native software & Capture One gives the best raw output compared to LR etc.

Of the few times I have used LR & PS, I noticed my D500 files were a touch soft. Not sure how things have changed now.

 

[EricBowles]

One of the big differences in the Z lenses is the corner sharpness - especially with normal and wide lenses. The wider mount allows more flexibility for lens designers to minimize distortion and optimize sharpness across the frame. On several lenses I've noticed the center sharpness is similar to recent designs, but the mid-frame and corner sharpness has improved a lot. If you are stitching panoramas or have detail outside the frame center, this is important. For longer lenses the mount makes much less difference since you are not bending light to such extreme levels at frame edges. That's part of why Nikon did not prioritize long lenses - the optical difference was minimal using the FTZ. Of course, newer long lens designs and newer technologies usually mean sharper, fewer artifacts and corrections, and faster focus.

 

[sid_19911991]

One of the big differences in the Z lenses is the corner sharpness - especially with normal and wide lenses. The wider mount allows more flexibility for lens designers to minimize distortion and optimize sharpness across the frame. On several lenses I've noticed the center sharpness is similar to recent designs, but the mid-frame and corner sharpness has improved a lot. If you are stitching panoramas or have detail outside the frame center, this is important. For longer lenses the mount makes much less difference since you are not bending light to such extreme levels at frame edges. That's part of why Nikon did not prioritize long lenses - the optical difference was minimal using the FTZ. Of course, newer long lens designs and newer technologies usually mean sharper, fewer artifacts and corrections, and faster focus.

Yeah looking forward to the 200-600 Z lens.

 

[ElenaH]

newer long lens designs and newer technologies usually mean sharper, fewer artifacts and corrections, and faster focus.

excellent observation!
I have else observed (for example by testing Tamron 70-200 vs. Nikon S 70-200 on Nikon Z7) that Nikon Z gathers more light and can go with lower ISO under the same circumstances and settings (shutter speed and aperture are the same, auto ISO shows better results for the native lens). It is about 1/3 or 2/3 stops, not much but nevertheless... I don't know if this can regard to the bigger mount/shoter flange or just to the lens ability to transmit the light (T-stop ref. DXOMark) Anyway, 1/3-2/3 Stops were not enough for me to buy the S-lens having Tamron alerady.
Interestingly, I also noticed it by shooting the same scenes with Z+300/4 and D850+Sigma 120-300/2.8. ISO on Z was better than on Sigma closed to f3.5. Z performed very good on f4. Perhaps we will see excellent teleptoho lens in the future... or maybe I am just a dreamer

 

[NorthernFocus]

...I have else observed (for example by testing Tamron 70-200 vs. Nikon S 70-200 on Nikon Z7) that Nikon Z gathers more light and can go with lower ISO under the same circumstances and settings (shutter speed and aperture are the same, auto ISO shows better results for the native lens). It is about 1/3 or 2/3 stops, not much but nevertheless... I don't know if this can regard to the bigger mount/shoter flange or just to the lens ability to transmit the light (T-stop ref. DXOMark)...

Your observations are interesting. The difference in ISO is no doubt related to the differences in T-stop. Lens f-stop is based purely on geometry. T-stop is actual measured light transmission to the sensor/film plane relative to what is entering the lens. The camera's meter is reading the light at the sensor and adjusts ISO accordingly. So yes a lens with better T-stop will allow lower ISO for the same f-stop setting and for a given scene/lighting conditions. The differences in T-stop between older F mount and newer Z mount lenses likely has to do with both the larger flange and newer/better glass/coatings. Net result is better light transmission(T-stop) for a given focal length and objective diameter.

 

[EricBowles]

Your observations are interesting. The difference in ISO is no doubt related to the differences in T-stop. Lens f-stop is based purely on geometry. T-stop is actual measured light transmission to the sensor/film plane relative to what is entering the lens. The camera's meter is reading the light at the sensor and adjusts ISO accordingly. So yes a lens with better T-stop will allow lower ISO for the same f-stop setting and for a given scene/lighting conditions. The differences in T-stop between older F mount and newer Z mount lenses likely has to do with both the larger flange and newer/better glass/coatings. Net result is better light transmission(T-stop) for a given focal length and objective diameter.

That's correct. One more thing to add to the equation is differences in metering and lens correction can affect the exposure. For example, the JPEG with the applied camera settings best reflects the way the camera meters. If there is vignette correction in the lens correction database - which would be normal for new Nikon lenses - it could affect the overall exposure of the frame. This depends a bit on how you meter as spot metering the center would have no impact, but matrix metering considers the entire frame and the location of your AF point. So it's possible the Z lenses are brighter because of correction and your metering choice. This is going to be especially true wide open where vignetting is usually most pronounced and the correction has the most impact.

 

[DavidT]

From what I have read that is supposed to be an advantage the Z mount has. However in the real world looking at some of the newer lenses such as 50 f1.2 lenses Sony who has the smaller mount has a sharper and more compact lens. I think it comes down to more of lens design than simply a bigger mount. Canon who's mount is also not as big as Nikon is producing some very sharp glass.

 

[EricBowles]

From what I have read that is supposed to be an advantage the Z mount has. However in the real world looking at some of the newer lenses such as 50 f1.2 lenses Sony who has the smaller mount has a sharper and more compact lens. I think it comes down to more of lens design than simply a bigger mount. Canon who's mount is also not as big as Nikon is producing some very sharp glass.

That's at least partly true. In the case of Nikon, the F-mount was the smallest mount and the Z mount is the largest. The F-mount made it very difficult to design fast medium and wider lenses, and with the larger Z-mount the new models can be fast and sharp all the way to the corners. That simply was not possible with the smaller mount. Not that the lenses are bad - there is more to a lens than ultimate sharpness across the frame. But characteristics such as bokeh and falloff needed to be designed as premium features over sharpness toward the frame edges. Now either approach is open - as well as faster lenses than would have been historically acceptable/possible. The Noct f/.95 lens is a good example of a lens that was not possible on the F-mount, but the f/1.2 designs are much easier to engineer and achieve now with the wide mount. Even with the f/1.8 primes, sharpness to the frame edge is available at a cost far less than previously possible.

 

[fcotterill]

Exactly, we have been seeing the benefits since the first Z lenses. A video / interview with Nikon engineers explained how Z mount architecture enabled them to design much more compact UWides - especially to bulbous front element.... Compare the 14-24 G and S versions.... The G model on F mount on its launch broke new ground for ILCs, but the Z has redefined this zoom.

There are also significant benefits for mounting filters, and smaller overall size <700g vs 1000+g. the 14-30 f4S allows a 82mm filter thread so one can use much narrower filters ie 100 instead of 150 system

Mount Wars: Guess what? Z-mount really DOES help lens design… and AF! (Nikon technical Q&A)

I had a chance to sit down with a group of top Nikon executives and engineering managers last month, as part of my yearly pilgrimage to Yokohama, Japan for the annual CP+ trade show. We talked about lens design and how it's…

www.imaging-resource.com

IR Interview: A deeper dive with the Nikon Z7 engineers

(See important update from 8/30/18 below, about low-light AF performance) I had a chance to interview a panel of three Nikon engineers at the recent rollout event for the Nikon Z7 in Tokyo, and ask them some of the questions we…

www.imaging-resource.com

One of the big differences in the Z lenses is the corner sharpness - especially with normal and wide lenses. The wider mount allows more flexibility for lens designers to minimize distortion and optimize sharpness across the frame. On several lenses I've noticed the center sharpness is similar to recent designs, but the mid-frame and corner sharpness has improved a lot. If you are stitching panoramas or have detail outside the frame center, this is important. For longer lenses the mount makes much less difference since you are not bending light to such extreme levels at frame edges. That's part of why Nikon did not prioritize long lenses - the optical difference was minimal using the FTZ. Of course, newer long lens designs and newer technologies usually mean sharper, fewer artifacts and corrections, and faster focus.

 

[fcotterill]

Here's are 2 accessible articles on field curvature and how the quality of lenses is measured, with key terms etc

What is Field Curvature?

photographylife.com

How to Read MTF Charts

photographylife.com

 

[NorthernFocus]

...So it's possible the Z lenses are brighter because of correction and your metering choice. This is going to be especially true wide open where vignetting is usually most pronounced and the correction has the most impact.

I think your confusing the issue of the lens being brighter vs the corrected image being brighter. What Elena pointed out regarding lower ISO values is a function of more light available at the sensor. IOW lens physics. Correcting vignette is simply in-camera PP.

...Sony who has the smaller mount has a sharper and more compact lens...

Well that's a given.

 

[sid_19911991]

Here's are 2 accessible articles on field curvature and how the quality of lenses is measured, with key terms etc

What is Field Curvature?

photographylife.com

How to Read MTF Charts

photographylife.com

Excellent share.

Only wish the 3 brands had the same standardized test. MTF of 500 PF looks miles better than the MTF on the SOny 200-600, which is not so the case in the real world.

 

[EricBowles]

I think your confusing the issue of the lens being brighter vs the corrected image being brighter. What Elena pointed out regarding lower ISO values is a function of more light available at the sensor. IOW lens physics. Correcting vignette is simply in-camera PP.

Well that's a given.

In Camera post processing is still relevant - and can affect exposure. Just something to be aware of in making comparisons.

 

[NorthernFocus]

In Camera post processing is still relevant - and can affect exposure. Just something to be aware of in making comparisons.

By exposure presumably you mean the image histogram versus the camera exposure settings. Clearly the case and a good point.