[Wheatfield]

Info from where of what?


With what?

If Wheatfield was right and the focal length info must come from a chip, perhaps if the camera gets info on aperture and maximum aperture, but no chipped identification, the computer simply assumes it's an A lens of some kind, and gives you the info from the focal length you input?

I'm now confused on the point of whether the camera should be reading an A lens's focal length in-camera, if you don't set it yourself. Anyone?


Sorry if I sound testy.

OK, forget my first post. It appears to be wrong. I checked several files and several lenses and all seem to have the correct lens information embedded from several different A series lenses, including an off brand Voigtlander Nokton.
It doesn't seem to matter if shake reduction was on or off either.
I find it quite interesting, since the lenses I am using predate EXIF data by a fair amount.
As a side question which might provide some insight, does anyone know when Pentax introduced the MTF programmed exposure option? This would have required lens information to be transmitted to the body.

Edit: My 600mm lens seems to not transmit itself to the camera, but my other A lenses do seem to.

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Last edited by Wheatfield; 02-04-2009 at 12:44 PM.

[southy]

Hrmm. i wonder if SR overrides the lens information then, because I distinctly remember accidentally setting my 135-A to 155mm in SR, and all my EXIF data was reporting it incorrectly.

[Just1MoreDave]

...As a side question which might provide some insight, does anyone know when Pentax introduced the MTF programmed exposure option? This would have required lens information to be transmitted to the body.

I think that is one difference between F and FA lenses. The chip is 4 bits in F lenses and 8 bits for FA, so FA lenses can have more data. I can't find where I read this.

[Ratmagiclady]

As far as I know, A-Lenses only report aperture. Not focal length. I generally use SR (Shake Reduction) which requires you to input your focal length. If you input your focal length, then it will be reported properly in the EXIF information.

At least this is true on my K100D. The general limitations are that you have to power cycle (the fastest way to set a new SR length) to switch lenses, and you have to round focal length to the nearest value in SR. There is another way to set SR length, but it is buried deep within the menus so I never bother.

I will have to go back and check my A-lenses when I get home, but I think this is generally the case.

-southy

OK. Thanks for that. I wasnt sure what Wheatfield meant about his last post, if he'd seen or was just speculating...


*scratching head looking at test shots on screen rather than LCD.* I guess this isn't *terrible,* but I'd been expecting better of this lens from reviews. Always so hard to tell when the user is hurting. Or, err. Some of this is pretty terrible. Who'd have thought digital would end up being so *vague?*

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Last edited by Ratmagiclady; 02-04-2009 at 01:01 PM.

[Ratmagiclady]

I think that is one difference between F and FA lenses. The chip is 4 bits in F lenses and 8 bits for FA, so FA lenses can have more data. I can't find where I read this.

Well, I've always got MTF stuff set, and I'd think if that were working, Program would set something more like f8 when available, than the 4 it seems to want with this lens.

I just need to figure out if this is right.

[MrApollinax]

Let's start from the beginning. Can you post a picture? Can you post any EXIF info as well. Like I said earlier my A50 f/2 lens works like a champ and I have taken several pictures with it so your A28 should behave similarly:

ISO: 800 - Exposure: 1/20 sec - Aperture: 2.0 - Focal Length: 50mm

[Ratmagiclady]

Let's start from the beginning. Can you post a picture? Can you post any EXIF info as well. Like I said earlier my A50 f/2 lens works like a champ and I have taken several pictures with it so your A28 should behave similarly:

Yes, I can do this. It may be slow. (My Internetting computer is maybe a bit old for 14 MP files, ....I'm at an awkward stage here where it's not made sense to upgrade computer till I had the gear to start working digital.... so I have this old IBM laptop, and also an old Mac with a not-very-good monitor all separate for doing basically nothing but imaging work, and household networking is a mess cause my beloved, kind of lost the password to our router. Nothing's easy. That's why I've been wanting to know how this lens *should* behave on the camera so I can tell if something must be terribly wrong before I try messing with focus adjustments or screens, ....there's just so many stages where things could be going wrong, and a couple of them could be within the camera or lens. )

So, anyway, after some wrangling, I can put stuff up on Photobucket, which tends to really screw the pooch about downsizing files this size for web use lately, or on FLickr, which might get testy about requiring links of certain kinds to go places which under IMG code get picky.... Either of these sites is actually the easiest way I have to read EXIF here, but are sometimes wrong, anyway.


*yanking out great wads of hair and politely shrieking.*

OK. Now I feel better. I'll get something up. .


(Oh, just to complicate things, *some* of my test shots, I manually inputted a focal length of *30mm* in hopes of seeing the difference on the LCD info report should the camera start recognizing the lens. I gave up on this eventually and started putting in 28mm.)

[MrApollinax]

We are all here to provide help (and color commentary) if needed. Are you shooting in Manual or in one of the other program modes?

[pasipasi]

When I use an 'A' lens, the exif gives this info:

Lens Type : A Series Lens

[Ratmagiclady]

OK, here's a pretty typical result. It's not the one I intended tto upload, first, so it's not one I'm dead-sure where the focus point was, (probably that screw nearest the center, or the mesh dead-center) but everything seems to end up coming out not much better than this.

[Canada_Rockies]

The A lens doesn't have a chip, so the camera has nothing to recognize. Input focal length manually when the camera asks for it on startup. You will not have FL available in EXIF though. (Atleast not that I've been able to make happen).

Lightroom seems to recognize the focal length when I use my 400. I have focal lengths in the EXIF showing 400 and 550 (the closest I can get to 560 = 400 x 1.4) with the convertor. K10D and output is PEF. I have not checked to see if DNG drops some EXIF data.
[EDIT] Here's the EXIF data from the first image in my Flcikr stream with the 400/5.6 M lens. I entered 400mm as the focal length for the shake reduction on startup. This is not in the manufacturer's segment, but the lower segment with the exposure data. I have highlighted the appropriate line. The image was taken in RAW/PEF on the k10d during some testing on the exposure variations with the meter in the newer digital cameras.

* Exposure Time (1 / Shutter Speed) = 1/180 second = 0.00556 second
* Exposure Program = manual control (1)
* ISO Speed Ratings = 400
* Exif Version = 0221
* Original Date/Time = 2008:03:06 15:55:47
* Digitization Date/Time = 2008:03:06 15:55:47
* Shutter Speed Value (APEX) = 7491853/1000000
Shutter Speed (Exposure Time) = 1/180 second
* Exposure Bias (EV) = 0/10 = 0
* Metering Mode = center weighted average (2)
* Flash = Flash did not fire, compulsory flash mode
* Focal Length = 40000/100 mm = 400 mm
* Image Sensing Method = one-chip color area sensor (2)
* Colour Filter Array (CFA) Geometric Pattern = 0x02,0x00,0x02,0x00,0x00,0x01,0x01,0x02
* Custom Rendered = normal process (0)
* Exposure Mode = manual exposure (1)
* White Balance = auto (0)
* Focal Length in 35mm Film = 600
* Scene Capture Type = standard (0)
* Contrast = hard (2)
* Saturation = normal (0)
* Sharpness = hard (2)
* Subject Distance Range = distant view (3)

[Ratmagiclady]

We are all here to provide help (and color commentary) if needed. Are you shooting in Manual or in one of the other program modes?

This has been, in general, all over the place. (partly in hopes of figuring what's up with the lens and computer talking) I haven't been paying too-careful attention to exposure, generally either picking something straightforward for the meter to point at or setting in manual, or hastily comping things as necessary. Certain amount of aperture priority or av-via-program to get the aperture I wanted to test.

FYI, EXIF is nice, but the real question here is is the *camera* operating properly, (also, is the lens up to snuff or do I have a bad one) and if so, why is he telling me odd things in some menues?


Here's another image, in pretty close and at F11. One of the better ones I've been able to get.

[MrApollinax]

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?

[richard64]

I just checked a PEF I took with my A 50 f/2 in PhotoMe and it actually shows under lens data "smc PENTAX-A 50mm F2." I had thought for sure that inputing the focal length would make the FL show up in EXIF but I just noticed that the full lens name came up in EXIF. Maybe you are refering to the M lenses?

PhotoMe is clever, isn't it? It says that at 0x207 is a LensInfo collection of bytes (44 bytes) and from this it can determine the lens type, and the f-number range.

Richard

[Nowhere Matt]

I was recently surprised as well when I put an old 50mm A f2 on my K10. After a day of forgetting about the aperture ring permission setting, taking some pictures and then loading a few to flickr. The exif notes were a foot long and contained every letter in the alphabet and a thousand numerals.
I'm telling the thing is ten times as long as the PhotoMe example above.