[orly_andico]

I have been using screw mount Pentax lenses that I bought in 1975 with my K200D and K20D for over two years. I have no problems with metering with those lenses on either camera. If you think that any camera is going to automatically give you a correct exposure under any circumstance, you are going to have grief with any system you buy into.

But you seem determined. The Nikon is a great camera. Good luck with it.

I don't have (nor plan to get) the D7000. I was merely pointing out that it has better old-lens compatibility than any Pentax.

I agree about exposure. But two stops out? consistently? seems rather excessive. And this error is present even if you meter on a blank wall so it's not a backlighting situation or anything. The inconsistency in metering with M42, K, and M lenses is very well known, I'm surprised that more people don't consider it an issue.

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Last edited by orly_andico; 12-29-2010 at 10:39 PM.

[Blue]

I fail to see the downside with the D7000. Nikon primes are cheap (e.g. the highly rated 180mm f/2.8 ED can be had for $450.. try to find something similar in Pentax-land).

And the D7000 can meter even with their old manual focus lenses (something no Pentax DSLR can do). I find it funny that Pentax talks about all the millions of manual focus Pentax glass, but can't meter properly. My (old new) Canon 40D can meter much more accurately than my K20D with screw-mount glass! and the D7000 has the aperture-coupling cam so it can sense the aperture on their old glass (they do talk about the 24 million Nikkors out there). that aperture cam is something that disappeared from Pentax SLR's in the 1990's with the crippled KAF2 mount.

The Nikon lenses I'm interested in aren't cheap. Sure they have some good cheap primes, but so does Pentax.

[Pentaxor]

I'm not sure about you guys but both my K10D (now sold) and K20D meter wildly out with M or K lenses.

I believe this is well-documented. It's under-exposed by two stops at f/1.4, one stop at f/2.8, it's about bang-on at f/5.6 to f/8, then over-exposed one stop at f/11.

I can't be expected to remember those %$%$#! offsets every time I press the green button.

By contrast the 40D I just picked up, sure it can't stop down those M42 lenses with the green button, but it meters accurately (within 1/3 stop) in Av and M modes. It does over-expose by about 1 stop at small apertures (f/11 and up). But I don't use old lenses at small apertures anyway on Canon because focusing gets really tough.

On Pentax, yes, you can use small apertures because the body gives mechanical stopdown. But the metering is so wacky and weird, it's not funny.

There's no point comparing the Nikon 180/2.8ED with the A* 200/4. Just look at the price differential.

My point is.. excepting the pre-Ai lenses which don't have the indexing ring, Nikon has a manual-focus range (cheap) that's even bigger than what Pentax has (for K-mount). I wasn't talking about M42. And, while both Nikon and Pentax talk about compatibility with older lenses, the reality is that Pentax metering on M- and K-lenses (and M42 for that matter) is downright incompetent, while the D7000 (and the D200, 300, 700, 3, 2, and 1 before it) all can meter properly on Ai-S lenses and later.

The remapping of bad pixels is impressive and useful (K20D has it as well) but aside from my K20D I haven't seen other cameras with bad pixels! maybe I didn't look closely enough or use those other cameras long enough.

price differential comes with rarity and reputation. I believe some Nikon and Canon lenses have lenses that are expensive. saying that all manual focus Nikon lenses are affordable is not entirely true. some old and highly reputable old manual focus Pentax lenses are cheap as well.

anyway, saying that old Pentax lenses meter badly and as you were saying 2 stops under is extremely far-fetched and very hard to believe, if not downright impossible.

as far as bad pixels are concerned, I would assume what you said about not looking close enough and used long enough.

[orly_andico]

anyway, saying that old Pentax lenses meter badly and as you were saying 2 stops under is extremely far-fetched and very hard to believe, if not downright impossible.

downright impossible?

on this very forum:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/16834-k10d-stopped...weirdness.html

Read in particular the postings of Lowell.

https://www.pentaxforums.com/forums/pentax-dslr-discussion/75238-k20d-metering-m-lens.html

"This issue has been beaten to death already.." i.e. it is a well-known shortcoming. I just squeezed off a few shots with my Pentacon 135mm f/2.8 -- my memory is correct, 1 stop under-exposure at f/2.8, about correct at f/4, then gets progressively over-exposed as I stop down. This is with the latest K20D firmware (1.04).

Or this

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/60081-usage-green-button.html

where Peter Zack (whom I read a lot on photo.net forums and whom I consider an authority on these things) states that

In most cases, these lenses meter well wide open but tend to over expose in middle apertures. So you use the green setting recommendations as a starting place to adjust to the correct exposure.

Now in my experience, metering is correct around f/4. You can still live with it at f/2.8 (it's like exposing to the left). But definitely at f/1.4 it's two stops under-exposed.

I'm not incompetent, and I've used a K10D and now K20D for almost three years. I'm not imagining this metering weirdness.

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Last edited by orly_andico; 12-30-2010 at 12:32 AM.

[Pentaxor]

downright impossible?

on this very forum:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/16834-k10d-stopped...weirdness.html

Read in particular the postings of Lowell.

https://www.pentaxforums.com/forums/pentax-dslr-discussion/75238-k20d-metering-m-lens.html

"This issue has been beaten to death already.." i.e. it is a well-known shortcoming. I just squeezed off a few shots with my Pentacon 135mm f/2.8 -- my memory is correct, 1 stop under-exposure at f/2.8, about correct at f/4, then gets progressively over-exposed as I stop down. This is with the latest K20D firmware (1.04).

Or this

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/60081-usage-green-button.html

where Peter Zack (whom I read a lot on photo.net forums and whom I consider an authority on these things) states that

In most cases, these lenses meter well wide open but tend to over expose in middle apertures. So you use the green setting recommendations as a starting place to adjust to the correct exposure.

Now in my experience, metering is correct around f/4. You can still live with it at f/2.8 (it's like exposing to the left). But definitely at f/1.4 it's two stops under-exposed.

I'm not incompetent, and I've used a K10D and now K20D for almost three years. I'm not imagining this metering weirdness.

thank you for the references. aside from yourself, where specifically did someone mentioned that it underexposes by 2 stop and by whom?

aside from that, you said that it is well-documented, so you are very much aware on what shooting modes you need to use with and what type of metering system to get proper exposure. underexposing shouldn't be a problem by then.

anyway, what makes you think that a D7000 would meter better where the example that you had given is that of a 40D which is not even a Nikon but a Canon? I'm just arguing with the point of how a Nikon metering discussion became a Canon metering discussion. not to mention that dpreview mentioned a serious metering issue with the D7000, so at which part does it make it sound better with metering? can you explain what dpreview meant by that or are you arguing based on the spec sheet?

anyway, if you are happy with the Nikon's so-called "perfect" metering system, then go for it. but you can't force me to believe that Nikon meters better.

[orly_andico]

I'm not familiar with DPR's report on metering inaccuracy on the D7000.

The two-stop underexposure is my experience with an f/1.4 lens (Super-Tak). But many other people report a similar "curve," e.g. it's wildly under-exposed at very wide apertures, is pretty correct from f/4 to f/5.6, then gets over-exposed as you stop down further.

https://www.pentaxforums.com/forums/pentax-dslr-discussion/25931-k10d-my-old-...tml#post228108

My experience is similar for all non-A lenses. For large apertures (under f/5.6), I get underexposure (about 2 stops at f/2). For smaller apertures, (over f/11), I get overexposure (about 1 stop at f/22).

http://photo.net/pentax-camera-forum/00Krj8

The K10D's green-button stop down metering mode above will tend to overexpose a bit unless the lens is at wide open aperture. If you're shooting at f/5.6 or f/8 with an f/2 lens, cutting exposure time by a factor of two stops (ie: 1/100 sec becomes 1/400 sec) will usually get you closer to the right exposure.


http://forums.dpreview.com/forums/read.asp?forum=1036&message=34242004

Stop-down metering in M mode + Green button with manual lenses is just as poor as with the previous models I've used: K20D, K10D and *ist DS. The error increases as the aperture decreases.


and again, on this very forum (check Lowell's graph.. it shows the same curve that I report). Another poster does report that the K-x is more accurate (only 1 stop under-exposed at f/1.4, roughly correct from f/2 to f/11, over-exposed one stop at f/16).

https://www.pentaxforums.com/forums/pentax-dslr-discussion/86746-accuracy-k-x...42-lenses.html
https://www.pentaxforums.com/forums/pentax-dslr-discussion/90344-green-button...nual-lens.html

https://www.pentaxforums.com/forums/pentax-dslr-discussion/39189-metering-man...asperated.html

The reason why Pentax metering with old lenses is dodgy, is because they removed the aperture-sensing prong from the body. Look at any old Pentax film camera and you'll find that prong, which physically senses the position of the aperture ring. That's why all Pentax DSLR's have a crippled KAF mount.

http://kmp.bdimitrov.de/technology/K-mount/crippled_AF.html

My point was, the D7000 does have that prong, and is the first consumer Nikon body to have it (the D1/2/3/700/200/300 all have that prong). No Pentax DSLR has ever had that prong. Which reduces Pentax's claims of compatibility with old lenses.

Now getting back to the fact that Pentax metering is well-documented to be dodgy. As I said, at f/1.4 you press the green button, then decrease the shutter speed by 2 stops. Or 1 stop at f/2.8 (and so on). It can be worked around. But it's damn annoying. In-camera metering is not supposed to require compensation every time you take a reading.

Now as for the actual metering performance of the D7000, I won't try to guess since I have no interest in Nikon anyway. I however applaud their effort to maintain compatibility with old, old lenses by putting that prong on the D7000. I don't understand why el-cheapo old Pentax SLR's had that aperture-sensing prong and then Pentax took it off (back in the film era, even the MZ-50 didn't have it anymore, but the MZ-5 had it and of course the MZ-S).

I would gladly pay $100 more for a DSLR that had that prong, but apparently even on Pentax's top-end digital body they can't be bothered to restore that feature.

[Manel Brand]

I'd be massively impressed if this were true, as I've been using K10D and K20D for over three years now and could never get this mythical metering working properly.

Yeah, blame the camera... and don't think about what are you missing.

[orly_andico]

Yeah, blame the camera... and don't think about what are you missing.

Your post adds nothing to the discussion, and instead descends into a personal attack.

[Manel Brand]

Your post adds nothing to the discussion, and instead descends into a personal attack.

Sorry, no personal attack intended. What do you want to be added to the discussion? We are not discussing manual exposure, are we? I understand you are using the green button technique. Perhaps the problem lies within a misuse of that.

[titrisol]

I saw your thread on pnet and tested the lenses I had at hand M28/2.8 and 100/4 and M42 50/1.4 and 55/1.8 at home (controlled lighting) with the lowly KX

I could not see differences in metering at fully open; middle of road (2stops); and fully closed; maybe +/- 1 stop which is quite irrelevant on the field.
I'll try to make nice graphs like Lowell's but doubt I can be so thorough and accurate

I'm aware that the Pentaxes since the MZ/ZX series came without the mechanical coupling; that maybe a minus but most people do not seem to notice it...
I tried the Nikon D70 (no prong) years ago with AiS nikkors and also did an OK job if you had patience

Now, let's try finding a hack!!!

I agree about exposure. But two stops out? consistently? seems rather excessive. And this error is present even if you meter on a blank wall so it's not a backlighting situation or anything. The inconsistency in metering with M42, K, and M lenses is very well known, I'm surprised that more people don't consider it an issue.

[Daveinozbikes]

Geez...is that it??????

Just starting to enjoy this post !!!!

[Adam]

So thank you Pentax and all the members of Pentaxforums.com for your contribution towards my growth in the last three years. I wish to continue as a member of this forum unless the moderators feel otherwise

That's perfectly fine- just be sure to post in the off-brand section! I'm moving that thread over there.

Note that there's no restriction on posting off-brand photos in the gallery or photo sharing forums, either

[orly_andico]

I have not verified but others say the K100D / K110D are much more accurate. I would assume the K-x is the same. And I do not agree that +/- 1 stop error is irrelevant in the field. With all the talk of 12-bit and 14-bit sensors, throwing away an entire stop is throwing away one bit of dynamic range. If I were satisfied with a +/- 1 stop error, I might as well use "Ultimate Exposure Computer" and just guesstimate.

[B Grace]

Stop-down metering is, in fact, only a modestly accurate means for metering with lenses having no aperture reading connection to the camera. While I think the two full stops error comment to be interesting I do often find my K200D meter to be a shutter speed or two off from what I find to be accurate when I shoot with my pre-A lenses.

The errors with stop-down metering aren't related to the aperture chosen but rather the desired conditions for a given shot. The camera has no idea of what the maximum aperture is for the lens so it must assume the light it is receiving is gray card typical. There are so many parameters involved in such a situation it is impossible for any software to correctly nail stop-down metering every time.

I do find the metering of my K200D with M42, K and M lenses to be close enough maybe 95% of the time and I really like the camera offering exposure comp with a simple click of the command dial to adjust shutter speed. This is as good as it may ever get so the solution is using current lenses with any current camera including the Nikons.

Finally, there are still a few vendors that have original Nikon Ai indexing kits in stock for some of the popular pre-Ai Nikkors. And there are a couple of machinists still offering their services. It's not a big deal. Other than maybe the multi-coated, last pre-Ai version of the 105/2.5 though I'm not sure there are any pre-Ai Nikkors I would pay to have Ai indexed.

[Pentaxor]

Sorry, no personal attack intended. What do you want to be added to the discussion? We are not discussing manual exposure, are we? I understand you are using the green button technique. Perhaps the problem lies within a misuse of that.

you said it best there my friend. I stop here since I decided not to feed the troll.