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01-07-2010, 07:06 AM   #1
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Firmware and lenses

I'm curious about this, regarding the meter issues with different dslrs and old lenses (or adapted lenses of any kind). Most of the problems derive from the camera having to use stopped down mettering because of the lack of maximum lens aperture info. Since the focusing screens light transmitting properties are not lineal as the apertures vary you have those deviations from correct exposure.
My question is, as you can dial the lens length in for SRV with manual lenses, couldn't a firmware update provide for a way to throw in all the other info (max aperture alone would account for all the mettering issues, I believe)?
Better than that, you could have user-created presets for each lens, you would just have to select them manually instead of the camera recognizing them automatically as it does with newer lenses. This all sounds quite simple and feasible to me, unless i'm missing something here, what do you think?


Last edited by max889; 01-07-2010 at 07:21 AM.
01-07-2010, 05:32 PM   #2
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I argued this point with pentax for 2 years with respect to the lack of accuracy of the K10D metering with my Manual lenses. I even went as far as asking them if they would re-calibrate my metering to use the *istD focusing screen (since the screen would upset metering with A lenses on the K10D but meter correctly with manual aperture lenses)

in a word, they said NO

You are more than welcome to try for success where I and others have failed.
01-07-2010, 06:27 PM   #3
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IMO it would be enough if Pentax made a DSLR with a fully supported K-mount.
The the light meter would work as it should, and no need for stop down metering.
The camera would not know which aperture used on fully manual lenses, but would know how much the lens is stopped down.

If wanting to have the aperture being displayed in the viewfinder and saved in the pictures max aperture of the lens has to be entered in the camera.

With the "crippled" K-mount used in all DSLR I don't think it would work with entering some basic lens parameters as the camera has no way of sensing how much the lens is stopped down if the lens is fully manual. The only way to have it work would be that you enter max aperture of the lens and the aperture used at the moment. So every time you change aperture on the lens you have to set the same aperture value on the camera.

Last edited by Fogel70; 01-07-2010 at 06:35 PM.
01-07-2010, 07:43 PM   #4
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Thanks guys. I wouldn't ask as much as a change in the mount works, but accepting the stopped down mettering is the only way to go, making manual input of the lens max aperture available would be just a software thing. The camera calculations for the focusing screen's light transmitting properties is something done once, then, with the max app input every lens would behave properly. I think it would be a minor software thing, It just makes you wonder why not doing that. It would make an enormous amount of lenses work almost seamlessly.

01-07-2010, 07:52 PM   #5
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I guess you have to ask how long a manufacturer feels too offer 100% backwards compatibility.

The KA mount was introduced in 1983 I believe.

The fact that every camera pentax makes today still can use these lenses (ok some meter better than others) is far superior to any other maker.

But I agree, a little software could make them meter better, even if they don't put the aperture coupling.
01-07-2010, 08:06 PM   #6
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I guess backwards compatibility is a good marketing concept but just as long as it doesn't cannibalize too much on new lens sales. There are so many lenses in K mount that making extreme compatibility efforts would only lead to less new lens sales. I guess it depends on consumer profile. New photographers who buy Pentax are more into learning how things work than Canon or Nikon customers, I think. So It's not an easy market to please, and one able to work around having to always buy the latest newest thing, if given the chance.
01-08-2010, 03:45 AM   #7
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As I said, I don't think it will help much by inputting max aperture of the lens as long as the camera don't know which aperture is used when stopping down.
01-08-2010, 06:05 AM   #8
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QuoteOriginally posted by Fogel70 Quote
As I said, I don't think it will help much by inputting max aperture of the lens as long as the camera don't know which aperture is used when stopping down.
I think you missed the point a little, based upon the long running discussions regarding stop down metering and manual lenses.

there are 2 things manual lens users would like, one of which is possible, and relatively simple, the other which while possible, is probably never going to happen because it will be somewhat less reliable.

I will deal with the second point first.

Ideally, a manual lens user would input maximum and minimum aperture, set the lens to minimul aperture and let the camera control the lens through the aperture activation lever. While this can work, the biggest problem is that the pentax K mount lenses controlled the aperture diameter linearly, where as KA lenses control the aperture area linearly with movement of the activation lever. As a result, if you consider stopping down to smaller apertures, exposure control would be extremely difficult because of the non linearity of movement. Also each lens would be scaled differently in terms of f-stops and amount of movement. There is no gaurantee what so ever on third party lenses, where they may have used the lever almost as an of / off switch, or something different depending on what suited thier production. As a result while perhaps better than nothing, exposure would not be what people have come to expect.

Now for the one they should do.

if you entered maximum aperture, then pentax could compensate for the non linearities of the viewing screen and metering system just as they do on KA lenses, and by pressing the green button, and using the difference in exposure between wide open metering and stopped down metering, make a very accurate corrected metering, as well as calculating the set F stop of the lens It would slow down the green button function a little, but because it could also calculate the preset aperture, P-TTL flash could work. I would love to see them do this.

01-08-2010, 07:22 AM   #9
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On "the one they should do", that 's what i was talking about Lowell. Basically you'd get the same metering as with any other lens. You'd have to stick to stopped down metering but it would be perfectly accurate through the whole range.
I just think of a different menu when you turn the camera on with a non A lens attached: a user generated preset list where you see your 135/2.5, choose it, and there, the camera knows just that, it's 135mm and f/2.5. And just that is plenty. You just preload all your manual lenses and everything would be a breeze.
01-08-2010, 07:32 AM   #10
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QuoteOriginally posted by max889 Quote
On "the one they should do", that 's what i was talking about Lowell. Basically you'd get the same metering as with any other lens. You'd have to stick to stopped down metering but it would be perfectly accurate through the whole range.
I just think of a different menu when you turn the camera on with a non A lens attached: a user generated preset list where you see your 135/2.5, choose it, and there, the camera knows just that, it's 135mm and f/2.5. And just that is plenty. You just preload all your manual lenses and everything would be a breeze.
Yes, but what about non pentax lenses?

Also if you put all pentax lenses into this, it is a really big list, as opposed to focal length and max aperture pick lists which are simpler to manage separately. Boot the camera, ask for focal lentgh and then ask for aperture.
01-08-2010, 07:34 AM   #11
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QuoteOriginally posted by Lowell Goudge Quote
if you entered maximum aperture, then pentax could compensate for the non linearities of the viewing screen and metering system just as they do on KA lenses, and by pressing the green button, and using the difference in exposure between wide open metering and stopped down metering, make a very accurate corrected metering, as well as calculating the set F stop of the lens It would slow down the green button function a little, but because it could also calculate the preset aperture, P-TTL flash could work. I would love to see them do this.
Ok, this might work, not sure how accurate it will work IRL though.

I would much prefer if Pentax put back the "stop-down coupler". I think Pentax could do that in K7 level of cameras without much added cost. With this the aperture ring will be fully supported on all K-mount lenses and have a fully working "live" light meter. Nikon has very good support for manual lenses on "serious" cameras, which I think is made by mechanical detection of the aperture ring.

I don't really think better working manual lenses will affect sales of new AF-lenses much. The biggest limiting factor on sales of these lenses is the price.


But I don't think Pentax will change anything on how manual lenses is handled, no matter how much we want it.
01-08-2010, 07:56 AM   #12
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Fogel, it would be as bit as accurate as with the new lenses. I don't think those give the camera any magical info besides that.
Lowell, yep, that would be another way of fixing that. I only thought if you switch between a few lenses a lot in the field presets would be faster. Anyway, that's only software, it's a very simple path to making everybody happy.
01-08-2010, 07:56 AM   #13
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QuoteOriginally posted by Fogel70 Quote
Ok, this might work, not sure how accurate it will work IRL though.

I would much prefer if Pentax put back the "stop-down coupler". I think Pentax could do that in K7 level of cameras without much added cost. With this the aperture ring will be fully supported on all K-mount lenses and have a fully working "live" light meter. Nikon has very good support for manual lenses on "serious" cameras, which I think is made by mechanical detection of the aperture ring.

I don't really think better working manual lenses will affect sales of new AF-lenses much. The biggest limiting factor on sales of these lenses is the price.


But I don't think Pentax will change anything on how manual lenses is handled, no matter how much we want it.
its not a stop down coupler, but an aperture ring coupler.

as for nikon's approach on serious cameras, there are a very limited few that you enter the apertures, and the camera controls the aperture like I described in the not likely to happen scenario, but their aperture control on the manual aperture lenses is linear with area, so they are ahead of the game in this respect.

Additionally, they only offer this on cameras more expensive than the K7 and not on every camera. the lower cost nikons give you only triggering the shutter, with no metering at all. Now that is what I call compatibility
01-08-2010, 08:09 AM   #14
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Fogel, you think older lenses working seamlessly wouldn't impact on new lens sales? May be for brands that invest heavily into zooms that's more true, but for the Pentax prime line it is a problem.
Zooms have improved A LOT so older ones will not compete. But good primes from the seventies on in many cases get as close in IQ to present ones as to be undistinguishable by the average guy. And they are better built than anything today, another selling point of the Limited lineup. If you can get everything but autofocus at a tenth of the cost, with products widely available, easily repairable, it will have an impact.
01-08-2010, 08:56 AM   #15
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I think there are less that less than 10% of Pentax DSLR users that use a prime lens, all other users only use AF zoom lenses.
Of those that use prime lenses there are very few that choose between a cheap MF lens or a expensive AF lens. The only reason most choose to buy a MF lens is because they are cheap, but if there was no MF prime lenses available they would probably not buy a much more expensive AF prime lens. They would only keep using the zoom lenses they already have. (Or maybe buy another cheap AF zoom lens)

Even if 5 times as many would start using MF lenses if Pentax improve MF lens handling, it would affect much less that 1% of Pentax total sales in new lenses.
The sales of AF might even rise if more use MF lenses as some want to upgrade to AF later on for easier handling.
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