Very interesting discovery about (D) and non (D) lenses

Started Apr 20, 2005 | Discussions
Dalibor J
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Very interesting discovery about (D) and non (D) lenses
Apr 20, 2005

Hello,
I would like to share with you my latest discovery,
which I think is very interesting one.

As you probably know Dynax 7D does not store the
information about focus distance into EXIF (SubjectDistance)
which is strange as the older models 7i..A2 did it.
This information is neither stored in MakerNote Camera Settings tag.
I thought that Minolta engineers decided to keep
this information private for some reason and I did
really miss it. This information could be quite useful
for various purposes, for example DxO software needs it to correct
lens distortions, it could be used by panorama software
and it will be very good for back-focus-problem hunters.

I was pushed by Mladen (www.dyxum.com) to try to search
for this info once more and it seems that I have found it this time.
I will try to release a new version of Dalifer soon
so all of you will be able to get this information from
your JPEG or MRW files.

And now comes the funny part. Let me start with simple question.
Q: What is the difference between (D) and non-(D) lens?
A: That's easy. (D) lens does report the focus distance
back to camera so it can use it for ADI flash (and maybe AS as well).

The reason why I have failed to find the focus distance value
few weeks ago was that I was trying to compare the data from
the picture taken with (D) lens to the picture taken with non(D) lens.
I was looking for something which is present in the first one
but absent in the second one. But I have no additinal information.

I have taken a different approach this time and I have managed
to find the place where the distance information is stored.
So I have tried to take some test shots with my 50/1.4 nonD lens
and I have found the distance information there as well!
Very interesting and confusing at the same time.

So let me repeat my original question.
Q: What is the difference between (D) and non-(D) lens?
A: Ehmmm. I really don't know. Anyone else?

Dalibor

CAClark
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Re: Very interesting discovery about (D) and non (D) lenses
In reply to Dalibor J, Apr 20, 2005

Perhaps it's to do with specific and slightly differing distance data to be shared with the attached flashgun?

Cheers!
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Craig A Clark
Lightwave 3D Modeller
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Stanley Kubrick Building
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Mob: 0779 5595016

http://www.pbase.com/caclark
http://www.f-nine.co.uk/

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ab012_KM7D
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Excellent Discovery!
In reply to Dalibor J, Apr 20, 2005

Well done!
--
Bernard
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KM7D - fantastic photography tool !!!

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Lazar
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Re: Excellent Discovery!
In reply to ab012_KM7D, Apr 20, 2005

I don't think the answer is important. The data you want is there. Good done. Reverse engineering is beauty work. I think to be fair you could talk with KM to be sure about your discovery.

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Dalibor J
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Flash?
In reply to CAClark, Apr 20, 2005

I am sorry, but I do not understand your answer.
The focus data is known even for non (D) lens and
it does not matter if the flash is attached or not.
The communication with the flash is done by the camera
not directly lens-to-fash.

Dalibor

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Dalibor J
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Re: Excellent Discovery!
In reply to Lazar, Apr 20, 2005

I don't think the answer is important.

Maybe it is not that important. But still I would like to know
why Minolta tells us to buy (D) lens to use the benefits of ADI flash metering,
when the non-(D) lens provides the same data.

you could talk with KM to be sure about your discovery

I really doubt that someone will reply anything meaningful.
I have tried to communicate with Minolta few times already
wit no success.

Dalibor

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Lazar
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Re: Excellent Discovery!
In reply to Dalibor J, Apr 20, 2005

Hi Dali,

Saying that you have the focal distance for non D lens, is not connected to the idea of using this data...

If KM says that D is used , so it is, even not available in the EXIF. EXIF is only for dumping out data for the user or some extraterestial software that can use it to change the parameters as much as possible for the shot.

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Magnus W
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Re: Excellent Discovery!
In reply to Dalibor J, Apr 20, 2005

Dalibor J wrote:

I don't think the answer is important.

Maybe it is not that important. But still I would like to know
why Minolta tells us to buy (D) lens to use the benefits of ADI
flash metering,
when the non-(D) lens provides the same data.

It doesn't -- the built-in distance encoder in the body provides this information. This has been the case since the i series, and is the reason Minolta cameras "reset" their auto focus as often as they can (bootup, MF/AF switching, "sleep" mode -- it's worse with older cameras).

It's even mentioned in old Minolta sales brochures that AF information is used for determining exposure (but not flash exposure AFAIK). That's why the 14-zone algorithm doesn't work in manual focus! In my opinion, the distance info gathered by older generation bodies is quite crude, probably divided in "zones" only.

"D" info is more refined and not delivered by the encoder. When using the "smooth focus" mode of the regular 7 and 7D, the body internal encoder is disabled. You can probably verify this with EXIF info!

you could talk with KM to be sure about your discovery

I really doubt that someone will reply anything meaningful.
I have tried to communicate with Minolta few times already
wit no success.

No surprise there

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Magnus W
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Re: Excellent Discovery!
In reply to Magnus W, Apr 20, 2005

An additional note: if you examine the EXIF data from the 135/STF lens I sent you, I am pretty sure there won't be any distance information. That is because the lens is manual focus and there is no connection through a focusing shaft, meaning the internal encoder can't do its work...

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Elgsdyr
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Re: Very interesting discovery about (D) and non (D) lenses
In reply to Dalibor J, Apr 20, 2005

Dalibor J wrote:

Q: What is the difference between (D) and non-(D) lens?
A: Ehmmm. I really don't know. Anyone else?

AFAIK, there's also some sort of distance information with non-(D) lenses but it's much more rough. Something like near/middle/far instead of a more precise distance.

-- hide signature --

Yours etc.
Torsten Balle Koefoed

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Dalibor J
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Lazar: Focus distance not Focal length
In reply to Lazar, Apr 20, 2005

Lazar,
I am talking about focus distance not the focal length.
Please re-read my post again.

Dalibor

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Dalibor J
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I'll try to verify how fine it is
In reply to Elgsdyr, Apr 20, 2005

there's also some sort of distance information with non-(D) lenses but it's much more rough.

It is possible, but I did not have this feeling on the first sight.
I'll try to compare how fine it is this evening and I will report back.

Something like near/middle/far instead of a more precise distance.

It is definitelly more precise than this, I know this already.

Dalibor

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Dalibor J
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Good points, Magnus
In reply to Magnus W, Apr 20, 2005

Those are very good points Magnus, thank you.

"D" info is more refined and not delivered by the encoder.

Are you suggesting that:

  • with non-(D) lens the info is taken from the encoder in the body?

  • with (D) lens the info is taken from the encoder in the lens itself?

This sounds reasonable. But even if this is true there still remains
some questions to be answered.
For example:

  • does the camera use the distance info even from non-D lens?

  • why the (D) lens needs to be "reset" at start when the

internal encoder is not used and the information is taken from the lens?

When using the "smooth focus" mode of the regular 7 and 7D, the body internal encoder is disabled. You can probably verify this with EXIF info!

Brilliant idea, I'll do it tonight.

if you examine the EXIF data from the 135/STF lens I sent you

There is "Infinity" in both files I have. So you are probably right.
Still there is a slight chance that it really was focused for infinity.

Dalibor

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CAClark
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Re: Flash?
In reply to Dalibor J, Apr 20, 2005

Who knows, I was just guessing

Cheers!
--
Craig A Clark
Lightwave 3D Modeller
Hard Surface

The Indestructible Production Company Ltd
Stanley Kubrick Building
Pinewood Studios
Iver Heath
Bucks , SL0 0NH

Mob: 0779 5595016

http://www.pbase.com/caclark
http://www.f-nine.co.uk/

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kiklop_2
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Re: Excellent Discovery!
In reply to Lazar, Apr 20, 2005

Lazar wrote:

I think to be fair
you could talk with KM to be sure about your discovery.

The point is that KM should be grateful to Dalibor for all his work in helping KM costumers.

Not so long ago, MRWFormat was the only raw converter that has produced great results in converting MRW files. And IMHO Dalifer is a brilliant little utility that has many unique features.

At least KM should provide Dalibor with needed information to save him a lot of time. Currently I'm testing DxO with KM lens modules and subject distance is the most important value. If not for Dalibor, DxO (excellent but a bit expensive) software would be of very limited use for 7D owners.

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7D dedicated website http://www.dyxum.com

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RichV
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More on D vs. non-D
In reply to Elgsdyr, Apr 20, 2005

Here's a quote of something I received a while back - hope it clarifies things:

"Distance is pretty much an exact item with the D lenses as they have a distance encoder built right into the lens whose data is decoded by the camera body. Non-D lenses do this by knowing travel distace of the lens from infinity to close focus and using a photo interrupter in the body to get very good (but not exact) distance. This information is used to get magnification data which is use for lots of stuff."

Rich

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Lazar
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Re: Lazar: Focus distance not Focal length
In reply to Dalibor J, Apr 20, 2005

Ok, but my answer is the same.

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tom
tom
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Re: Good points, Magnus
In reply to Dalibor J, Apr 20, 2005

With the earlier film cameras, such as the maxxum 7, there is a difference between how the distance info is obtained. With some of the newer cameras (5 and newer) it is different, and with the 7D I think it is a combination.

Those are very good points Magnus, thank you.

"D" info is more refined and not delivered by the encoder.

Are you suggesting that:

  • with non-(D) lens the info is taken from the encoder in the body?

The film cameras definitely do this - see below

  • with (D) lens the info is taken from the encoder in the lens itself?

With the maxxum 7 it takes info from both the lens and camera body encoders. The 5 has the capability of doing this also, but has a different way of using it. The 7 D also seems to be able to take from both.

This sounds reasonable. But even if this is true there still remains
some questions to be answered.
For example:

  • does the camera use the distance info even from non-D lens

All the cameras that use 14-segment ambient metering (7xi and later) use the data from the in-body encoder as part of the scene recognition and metering algorithms - primarily they use magnification of the subject (a function of focal length and focusing distance) and the difference between the subject and background (I think something like 'almost the same', a bit farther, really different, and 'off-scale different'). The various camera brochures and a couple of the HOVE books (7xi and 700si) get into some of the details.

When these cameras are put into manual focus mode, the in-body encoder was disconnected and the cameras would switch to an approximation of centerweighted metering. I have run a number of tests and the difference in exposure just by switching to manual focus is notable.

The 7 film camera was the first to keep the mechanical encoder connected when the camera was switched to manual focus (either on the front dial or with the push button on back). The AF motor was disconnected by a clutch. That's why there is still more resistance when turning the manual focusing ring. The 7 was the only camera that didn't switch to CW metering in manual focus. When resistance was too great (because of the use of teleconverters for example), the camera could be switched to 'smooth manual focusing' which disconnected the AF drive and the encoder and reverted to the earlier type of behavior.

The 5 has an additional feature that allows it to use the distance info from a "D" lens in the 14-segment metering and only switches to CW metering when a non-D lens is used in manual focus mode (body encoder disconnected). I think that the 60/70 also does this since its DMF only works with a "D" lens.

I tried using a "D" lens on the 7 in smooth manual focus mode to see if the 14-seg meter could use the D info from the lens encoder. It does not. I don't know if the 7D can or not. Just put the 7D in 14-seg mode with a D lens. Check exposure in AF and then set smooth manual focus and check the exposure again. Try to use a back lit or side lit subject so that 14-seg would be different than CW.

?

  • why the (D) lens needs to be "reset" at start when the

internal encoder is not used and the information is taken from the lens?

I think that the 7D still uses the mechanical encoder. I don't know if it uses the D-lens encoder for 14-seg.

When using the "smooth focus" mode of the regular 7 and 7D, the body internal encoder is disabled. You can probably verify this with EXIF info!

Brilliant idea, I'll do it tonight.

if you examine the EXIF data from the 135/STF lens I sent you

There is "Infinity" in both files I have. So you are probably right.
Still there is a slight chance that it really was focused for infinity.

Dalibor

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kiklop_2
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veri useful post, thanks (nt)
In reply to tom, Apr 20, 2005
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7D dedicated website http://www.dyxum.com

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Magnus W
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Re: Good points, Magnus
In reply to Dalibor J, Apr 20, 2005

Dalibor J wrote:
You got all the questions answered already I think, just this one:

if you examine the EXIF data from the 135/STF lens I sent you

There is "Infinity" in both files I have. So you are probably right.
Still there is a slight chance that it really was focused for
infinity.

If I remember correctly it was of a lamp in the ceiling, and actually focused on it. If it's "infinity" in the exif, that strengthens my point, as the camera resets focus to infinity and thus subtracts D info (coming from lens or built-in encoder). For a lens without D encoder it should be infinity -- by the way, why not examine a shot taken without any lens at all and see what the D info is set at?

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