[MrApollinax]

Oh there was a LOT more information in PhotoMe. That was just the summary notes. I left out the Flash, Lens, AE and RGB details. There is a TON of info for every picture you take if you know how to look at it

[Ratmagiclady]

Here is what PhotoME tells me:

[Overview]
URL: http://i186.photobucket.com/albums/x208/ratmagiclady/IMGP0350.jpg
File type: JPEG
File size: 578.3*KB
Creation date: 2/4/2009 13:48
Last modification: 2/4/2009 15:41
Make: PENTAX Corporation (PENTAX)
Camera: PENTAX K20D
Lens: smc PENTAX-A 28mm F2.8 or SIGMA Mini-Wide II 28mm F2.8
Software: K20D Ver 1.00
Dimension: 1024 x 680*px*(0.7 MP, 3:2)
Focal length: 28*mm*(equiv. 42*mm)
Aperture: F4
Exposure time: 1/45"
ISO speed rating: 400/27°
Program: Aperture Priority
Metering Mode: Center-weighted average
White Balance: Auto (White Fluorescent)
Focus Mode: Manual
Image Stabilizer: stabilized
Noise Reduction: Off
Flash: Flash did not fire, compulsory flash mode

BTW: The focus point according to PhotoMe is below the top right screw. Using photome's AE segment overlay a good portion of the center segments have the dark grates in them. I'm guessing that the camera's AE system metered against the darker portions of the picture which in turn would have blown out the highlights. What exactly about the picture is "not right" to you? And what is the camera itself telling you?

Wasn't worried about the highlights, there, just seeing some center sharpness somewhere between that screw and grid so I could figure out if everything's together right or if focus corrections were necessary or what. It looks about right, exposurewise.

Talking about no sharpness, here. Wondering if something's broken or has been tampered with, especially considering the camera can't seem to recognize focal length, as above.

Anyway, that focus point info sounds about right, I was, as I said, either going for that screw or the grid roughly dead-center in the frame (for easier chimping) I was pretty tired and frustrated, by then, but there should at least be a sharp zone somewhere in there at that aperture. (In camera sharpness is actually cranked a couple steps, too, just cause the JPEG readouts and outputs are always way soft whatever lens I use)

.

[Lowell Goudge]

in reading this I am surprised about the amount of posts for a simple issue.

SMC-A lenses and lenses that use a KA mount simply DO NOT report any lens info back to the camera.

If you look at a lens mount, say on your camera, there are 7 gold pins in the mount face (and 2 more below the mount on K100S, K200, K10, K20) of the 7 contacts, the furthest away from the lens locking pin (i'll call this pin 7) is a data link, that transmits focal length, lens type, focus distance etc.

on your lens if there are only 6 pins, or contacts (the maximum for a KA mount) there is no way to send data to the body.

of the remaining 6 pins, 5 are used for apature data (pins 1,2,4,5, and 6)

Pin 3 tells the body the lens is in the A position.

When you enter manually focal length, that is carried into the exif data, as evident in the posted photo showing 28mm in the photo of the air conditioner (I use Iexif viewer)

[Wheatfield]

As mentioned, PhotoMe pulled the correct lens info. You do have to manually enter the focal length into the camera at start up for the shake reduction. This is only done automatically with F and later lenses. It appears that pentax may have hobbled more than the lens mount when they started manking DSLRs, since it looks like the camera should be able to pick up focal length info off A series lenses.
Everything I've heard about the A28/2.8 is that it is a decent lens, but not a superb lens.
I ran your file of the air conditioner through Focus Magic and came up with this:

---

Last edited by Wheatfield; 02-05-2011 at 08:44 PM.

[Ratmagiclady]

in reading this I am surprised about the amount of posts for a simple issue.

SMC-A lenses and lenses that use a KA mount simply DO NOT report any lens info back to the camera.

If you look at a lens mount, say on your camera, there are 7 gold pins in the mount face (and 2 more below the mount on K100S, K200, K10, K20) of the 7 contacts, the furthest away from the lens locking pin (i'll call this pin 7) is a data link, that transmits focal length, lens type, focus distance etc.

on your lens if there are only 6 pins, or contacts (the maximum for a KA mount) there is no way to send data to the body.

of the remaining 6 pins, 5 are used for apature data (pins 1,2,4,5, and 6)

Pin 3 tells the body the lens is in the A position.

When you enter manually focal length, that is carried into the exif data, as evident in the posted photo showing 28mm in the photo of the air conditioner (I use Iexif viewer)

Well, I've been unable to get a particularly clear answer on that. This lens only has a few, I know it says max aperture and current aperture, ....for all I knew the absence of pins just meant it doesn't take as many others to say '28mm prime' as it might for a zoom or a longer lens or whatever. But if it takes a chip, it takes a chip.

I had the impression an A lens worked just the same as another.... and there's still the totally-unexplained claims on the LCD that the camera shot at a second or more when it *didn't* when I hit INFO but not when I'm in playback mode. That didn't seem right, however they're made.


(But, yes, these are from when I had manually entered 28mm in the camera. I think, the ones from when I'd manually set thirty may be somewhere around here. I've been swapping cards) I gather that none of this, apart from being a programmer's curiosity, can hurt anything or indicates bad service or fault in the lens? Humor the analog person. Basics. (Pardon my crankiness, there's some significant discomfort in my mind-camera interface today. )

[Ratmagiclady]

As mentioned, PhotoMe pulled the correct lens info. You do have to manually enter the focal length into the camera at start up for the shake reduction. This is only done automatically with F and later lenses. It appears that pentax may have hobbled more than the lens mount when they started manking DSLRs, since it looks like the camera should be able to pick up focal length info off A series lenses.
Everything I've heard about the A28/2.8 is that it is a decent lens, but not a superb lens.
I ran your file of the air conditioner through Focus Magic and came up with this:

What's Focus Magic do? My monitor's not really very good for pictures of this size, all I see are some apparent jagged artifacts in the mesh, like way too much sharpening. Which I usually don't. But there could be a lot of reasons for that. (like that image coming through Photobucket, not to mention how I set the JPegs in hopes of seeing where things actually have sharpness to find)
I really was expecting better results from this lens, somewhere, at least stopped down, whether I'm getting focus accurately or not...

I mean, understand, I'm just trying to verify if this equipment is functional, before I start messing with things downstream. It looks like an OK lens in the finder, not a great one, no, but I need non-embarrassing. And before I go trying to figure out how to make it work on the computer end, figure out what sensor and screen and file quirks work here, I need a sharp image to start with.

[Just1MoreDave]

I don't know if this will help much, but possibly a little. Here are some examples from my Pentax-F 28mm f2.8. It's the same optical formula as the Pentax-A, and this lens performs the same as my former A model - I checked before selling it. The first photo is a 793 pixel wide crop from a photo, no processing except the crop, done in Picasa:



Next, the same photo with Picasa's non-adjustable one-step sharpening:



The crop should eliminate any issues with resizing. The photo was at f8, 1/180s, ISO200, just about the minimum focus distance. Andy is often my lens test subject and the picture is pretty representative of what I expect.

[Marc Sabatella]

Wow, lots of confusion here. here are some of my observations:

- One of the basic questions has to do with focus adjustments. Those affect AF only. This is an MF lens. So no, the focus adjustment won't change a thing. It's ossible the focu screen is misalgined, or it's ossible you are being fooled by the fact that the focus screen shows a slightly deeper DOF than the lens actually produces at f/2.8, it's possible that the lens will not focus to infinifty any more, and it's possible that you simply need practice focusing manually on this camera. Seem to recall you come from a film background; you may be accustomed to larger viewfinders with split focus screens.

- Regarding transmission of lens info: it seems to me PhotoME is simply *guessing* based on the SR focal length entered and the minimum and maximum aperture reported by the lens (all of which *is* recorded in the EXIF). My A50/1.7 is reported correctly when I enter 50mm as the focal length in the SR menu, but if I lie and enter something else, PhotoME gets confused and makes other guesses (including 135/1.8 if I enter 28mm as the focal length). It may be a pretty clever a lot of the time, but it's capable of some gaffes as well.

[ edited ]

- Not sure what is going on with exposure. If I understand correctly, you are saying you hit the Info button while in Av or P mode and th displayed shutter speed is long. Well, you are pointing at something dark while doing so? It's going to display the shutter it thinks will be necessary at that moment. When I chimp the lCD, my natural tendency is to point the camera down at my feet. So of course I get a slow exposure...

- I'm also not sure what you mean about the focal length not being reported in the camera. If you've set in in the SR menu, and have SR turned on, then the rear LCD should display the focal length you entered. It does not display focal length when SR is not turned on.

[Ratmagiclady]

At least a doggie nose can't fail to cheer me up.

It's a thing that tends to make me nuts about the digital tech, though. How can you tell if your lens is in alignment if there's nothing to *look* at? It's all like electronic vapor... you're looking at it third hand. .... and how much stuff do you have to buy before you can see if any of it's any good?

At this point tonight, my eyes are too tired to see if the sharpened photo would be acceptable anywhere, though, never mind know why. How are ou even supposed to gauge exposure when it looks different on any monitor? I'm always wanting to stick a lupe against the screen, though I know *that* doesn't work. I dunno if it's the lens or the body or the screen or SR that makes it worse if you shoot too steady or some other setting or me... I thought optically correct was optically correct.

[Ratmagiclady]

Wow, lots of confusion here. here are some of my observations:

"- One of the basic questions has to do with focus adjustments. Those affect AF only. This is an MF lens. So no, the focus adjustment won't change a thing. It's ossible the focu screen is misalgined, or it's ossible you are being fooled by the fact that the focus screen shows a slightly deeper DOF than the lens actually produces at f/2.8, it's possible that the lens will not focus to infinifty any more, and it's possible that you simply need practice focusing manually on this camera. Seem to recall you come from a film background; you may be accustomed to larger viewfinders with split focus screens."


--Accustomed to larger finders, yes. Also, yes, faster lenses with generally narrower FOV's. The reason I broke down and got this 28 is in fact, cause apparently the focusing screen can't tell the difference, anyway, cause it's brightened for slower lenses, and disregards anything from wider than about 3.5 anyway.

Still, I'd expect to be finding *something* sharp in the field.

Don't care much for split screens and never did, though I wish the green hexagon were less vague, for when I *would* like a little help. If I had Pentax's ear, I'd have them make what I jokingly called my 'Ratzeye' screen, with a microprism for fast lenses for quick MF, around a matte circle which would allow critical focus and keeping an eye on the AF.

- Regarding transmission of lens info: it seems to me PhotoME is simply *guessing* based on the SR focal length entered and the minimum and maximum aperture reported by the lens (all of which *is* recorded in the EXIF). My A50/1.7 is reported correctly when I enter 50mm as the focal length in the SR menu, but if I lie and enter something else, PhotoME gets confused and makes other guesses (including 135/1.8 if I enter 28mm as the focal length). It may be a pretty clever a lot of the time, but it's capable of some gaffes as well.


Ah. OK. That was actually a theory I had voiced earlier, to try and reconcile all reports, but no one seemed to think much of it.

Apparently at least the SR part of the programming can't make this leap, so who cares, except posterity.

[ edited ]

"- Not sure what is going on with exposure. If I understand correctly, you are saying you hit the Info button while in Av or P mode and th displayed shutter speed is long."

When I make an exposure in seemingly anything but M or Tv (on the dial, not necessarily via hyperprogrammey things) ...it seems, by sound and results, the proper exposure happens. Say it's... 1/90 sec at 4.5. Exposure happens properly. Then, the chimping image comes up on screen. You hit 'INFO.' This information says maybe 6s 4.5. This report usually says it's in whole seconds. Unless I deploy the flash, then it reads 1/180 there.


OK. That's not right. RML makes annoyed sounds. Out of chimping mode. Hit the playback mode button. Voila. Exposure info says something at least like what actually happened. Probably this is the EXIF.

Still not sure if the initial problem means something is broken.


" Well, you are pointing at something dark while doing so? It's going to display the shutter it thinks will be necessary at that moment. When I chimp the lCD, my natural tendency is to point the camera down at my feet. So of course I get a slow exposure..."

This is the info about the exposure being reviewed.

"- I'm also not sure what you mean about the focal length not being reported in the camera. If you've set in in the SR menu, and have SR turned on, then the rear LCD should display the focal length you entered. It does not display focal length when SR is not turned on.

"


No, I was saying there that the camera was not registering the focal length without me setting it, despite the presence of contacts. This apparently is probably a separate issue, presuming certain programs are in fact inferring an A lens is present after the fact, rather than being able to know.


Also, how do you get it so you can tpe betweenquorted lines without it becoming all one block?

[Steinback]

To type between the line you break the text up into multiple quotes:

Wow, lots of confusion here. here are some of my observations:

"- One of the basic questions has to do with focus adjustments. Those affect AF only. This is an MF lens. So no, the focus adjustment won't change a thing. It's ossible the focu screen is misalgined, or it's ossible you are being fooled by the fact that the focus screen shows a slightly deeper DOF than the lens actually produces at f/2.8, it's possible that the lens will not focus to infinifty any more, and it's possible that you simply need practice focusing manually on this camera. Seem to recall you come from a film background; you may be accustomed to larger viewfinders with split focus screens."

--Accustomed to larger finders, yes. Also, yes, faster lenses with generally narrower FOV's. The reason I broke down and got this 28 is in fact, cause apparently the focusing screen can't tell the difference, anyway, cause it's brightened for slower lenses, and disregards anything from wider than about 3.5 anyway.

Still, I'd expect to be finding *something* sharp in the field.

Don't care much for split screens and never did, though I wish the green hexagon were less vague, for when I *would* like a little help. If I had Pentax's ear, I'd have them make what I jokingly called my 'Ratzeye' screen, with a microprism for fast lenses for quick MF, around a matte circle which would allow critical focus and keeping an eye on the AF.

- Regarding transmission of lens info: it seems to me PhotoME is simply *guessing* based on the SR focal length entered and the minimum and maximum aperture reported by the lens (all of which *is* recorded in the EXIF). My A50/1.7 is reported correctly when I enter 50mm as the focal length in the SR menu, but if I lie and enter something else, PhotoME gets confused and makes other guesses (including 135/1.8 if I enter 28mm as the focal length). It may be a pretty clever a lot of the time, but it's capable of some gaffes as well.

Ah. OK. That was actually a theory I had voiced earlier, to try and reconcile all reports, but no one seemed to think much of it.

Apparently at least the SR part of the programming can't make this leap, so who cares, except posterity.

[ edited ]

"- Not sure what is going on with exposure. If I understand correctly, you are saying you hit the Info button while in Av or P mode and th displayed shutter speed is long."

When I make an exposure in seemingly anything but M or Tv (on the dial, not necessarily via hyperprogrammey things) ...it seems, by sound and results, the proper exposure happens. Say it's... 1/90 sec at 4.5. Exposure happens properly. Then, the chimping image comes up on screen. You hit 'INFO.' This information says maybe 6s 4.5. This report usually says it's in whole seconds. Unless I deploy the flash, then it reads 1/180 there.


OK. That's not right. RML makes annoyed sounds. Out of chimping mode. Hit the playback mode button. Voila. Exposure info says something at least like what actually happened. Probably this is the EXIF.

Still not sure if the initial problem means something is broken.

" Well, you are pointing at something dark while doing so? It's going to display the shutter it thinks will be necessary at that moment. When I chimp the lCD, my natural tendency is to point the camera down at my feet. So of course I get a slow exposure..."

This is the info about the exposure being reviewed.

"- I'm also not sure what you mean about the focal length not being reported in the camera. If you've set in in the SR menu, and have SR turned on, then the rear LCD should display the focal length you entered. It does not display focal length when SR is not turned on.

(and no, I didn't add anything new to all that, I just changed the formatting)

[awo425]

Date Taken: 2005:06:26 05:16:20
Model: PENTAX *ist DS
Focal Length: 0 mm
Shutter Speed: 1/3000th sec.
Aperture: f 1.4
ISO: 200

This is part of the exif that I extracted from jpeg file. I took this picture in 2005 using istDS camera.
I am not using any software to read this EXIF. There was no SR in my camera, of course, lens I was using was SMC A 50/1.4

Camera have no clue about F.Length of the lens, because A lens will not transmit this info to the camera.

My guess is that if you enter FL in SR menu of the later Pentax camera like K20D, camera will guess the lens name and record it in exif, or the imaging software that you are using will guess it based on FL that you entered in SR menu.

As to SMC A 28 F2.8, it is OK lens, but nothing to write home about wide open.
I've used it for a while and eventually sold it. Too much distortion to my taste and nothing dramatical & f2.8

[Wheatfield]

As far as the camera knowing what lens is on it, I think I have an answer.
I took my A20mm f/2.8 off my K20 and mounted an A28mm f/2.8 and turned off the SR.
I then powered up the camera and took a picture.
I turned the camera off and turned the SR on, and then turned the camera on. I set 15mm into the SR when asked and took a picture.
I then repeated this, but put the correct (28mm) focal length into the camera.

In the first file, PhotoME called the lens either an A20/f2.8 or an A24/f2.8.
In the second file, PhotoME called the lens an A16/2.8 fisheye.
In the third file, it called the lens either an A28/2.8 or a Sigma Miniwide II 28/2.8.

So yes, it appears that there is some guesswork going on there.
As far as the sharpness goes, careful focusing, and perhaps stop the lens down a bit more should work.
FocusMagic is a bit brutal on small files.

[Marc Sabatella]

Still, I'd expect to be finding *something* sharp in the field.

Not if you missed focus by focusing too close, which is what I tend to do if I'm going to miss. Alos, there isn't much immediately behind the screen to gauge focus on - between the screen and house also seems plausible.

Try some more tests shots that have clearly visible areas in front of the target. I like to practice manual focus shooting my wood floor on an angle, aiming for particular knots.

[I]When I make an exposure in seemingly anything but M or Tv (on the dial, not necessarily via hyperprogrammey things) ...it seems, by sound and results, the proper exposure happens. Say it's... 1/90 sec at 4.5. Exposure happens properly. Then, the chimping image comes up on screen. You hit 'INFO.' This information says maybe 6s 4.5.

I've never seen anything like that. I don't suppose you could post a picture of your LCD doing that?

BTW; I just put " [ quote ]" and "[ /quote] ]" (without the spaces) around any text I want to quote, so i can intersperse my remarks.

[Ratmagiclady]

Thanks, especially to Stein for reposting that for me, I ended up giving in to an attack of the arthritis and sacking out. Sometimes I end up tuning it out till it gets really bad.

I do have the means to show the odd shutter speed readout, if you like. Though there's not much to see about it.

As for the nearer focus, I've done some other shots with nearer subjects, as well, and not seemed to get any better. I'd think with this focal length there'd be better DOF, anyway. I have a magnifying eyepiece on the way which may help: I'm not sure I'm actually getting focus when I think I am, in general, and my eyes have been fatigued since yesterday.