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03-11-2019, 02:15 PM   #1
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lens id question

I use a simple pp program which came with my Windows computer

when working on my new photos taken with a K 3 and a SMC Pentax-A 50mm F1.4 it ids as follows:

1/100 sec. f/5.6 55mm

the same lens used earlier this year it was ided as:

1/125 sec. f/2 50mm

other photos taken today from same camera but different SMC Pentax-A lens did id that lens correctly

any thoughts ?

03-11-2019, 02:29 PM - 1 Like   #2
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Those look like the exposure settings, rather than the lens id (which is unavailable for non-AF lenses). The focal length is based on the setting you select on the shake reduction prompt.

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03-11-2019, 02:33 PM   #3
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QuoteOriginally posted by Adam Quote
Those look like the exposure settings, rather than the lens id (which is unavailable for non-AF lenses). The focal length is based on the setting you select on the shake reduction prompt.
I posted the same reply, then removed it thinking I must have misread the post to begin with...seems I didn't. Shows you what you get when reading a forum late at night!
03-11-2019, 02:48 PM   #4
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there is no lens info on the exif that is correct

it is possible that I didn't set the number correct but I thought that it wasn't necessary for an " A " lens and number was the lens' focal length for a setting for the in camera SR system ?

what the PP program says is: file name, date and time taken, size, dimensions,

shot: 1/100 sec. f/5.6 55mm

ISO and device

????

it is the Windows " photo " editing program


Last edited by aslyfox; 03-11-2019 at 02:54 PM.
03-11-2019, 03:01 PM   #5
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I don't believe our cameras can identify the focal length for M or A lenses. I have both types, and I am almost always prompted to input the focal length, which is needed to help with the shake reduction. With an A lens, the camera can figure out the aperture, and that is about it. The shutterspeed and ISO are set in the camera, so those are always a given.

All that other information is going to be correct because it comes from the camera that way.

Now, if it is because it is a windows program, I would suggest finding another program to verify what you are finding (and if there is a problem). For instance, you could get Exiftool or any program that can reliably read the Exif record and verify what you are seeing.
03-11-2019, 03:13 PM   #6
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I'll try the lens tomorrow and make sure I set the number correctly

we will see what happens then

thanks for the suggestions
03-12-2019, 01:50 AM   #7
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Set it at 100 for the first shot then set it for 50 and if you see the exif match up you know whats up.
03-12-2019, 08:51 AM   #8
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A good, free image processor that is probably better than what came with Windows, is Fastone Image Viewer.

Its nowhere near as flexible or powerful as Photoshop Elements, or Lightroom, but its free and it will do all of the basics, such as resizing, cropping, color correction, etc.

03-12-2019, 10:22 AM   #9
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It's up to the software how the lens ID is interpreted.

With my Kiron 100mm f2.8 macro with KA mount:
Photoshop CS2 shows blank for lens and 100mm (which I set at startup for SR)
Zoner Photo Pro 17 shows "A series lens" and 100mm for FL
EXIF tool shows "A series lens" and 100mm
IrfanView shows nothing for lens and 150mm (equivalent) for FL.
03-12-2019, 02:19 PM   #10
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QuoteOriginally posted by noblepa Quote
A good, free image processor that is probably better than what came with Windows, is Fastone Image Viewer.

Its nowhere near as flexible or powerful as Photoshop Elements, or Lightroom, but its free and it will do all of the basics, such as resizing, cropping, color correction, etc.
Except it is not fully colour managed. Not a problem if you use a sRGB screen but if you use a Adobe RGB screen you will have problems
03-13-2019, 05:20 AM   #11
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QuoteOriginally posted by emalvick Quote
I don't believe our cameras can identify the focal length for M or A lenses. I have both types, and I am almost always prompted to input the focal length, which is needed to help with the shake reduction. With an A lens, the camera can figure out the aperture, and that is about it. The shutterspeed and ISO are set in the camera, so those are always a given.
This is correct - the lens ID is communicated by the 'digital' data pin, which did not exist before the 'F' series lenses. 'K' and 'M" lenses have no data pins at all, and the data pins on 'A' lenses only provide codes indicating the smallest and largest aperture the lens is capable of.
03-13-2019, 01:49 PM   #12
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QuoteOriginally posted by THoog Quote
This is correct - the lens ID is communicated by the 'digital' data pin, which did not exist before the 'F' series lenses. 'K' and 'M" lenses have no data pins at all, and the data pins on 'A' lenses only provide codes indicating the smallest and largest aperture the lens is capable of.
Ok that was my memory. I couldn't remember how exactly the A part worked other than it just did. I actually think I only have one A lens but many M lenses.

In my own workflow, I do often forget to change the focal length when attaching M lenses. I've not necessarily noticed any negative impacts or if they are there I just attribute them to user error; I don't turn off shake reduction, so in theory I could see issues. I mostly just edit the Exif record at the end of the day to reflect the lens I've used when using an M or A lens because I rarely use more than one different one in a day. This method obviously doesn't work if you only use M lenses. In that case, I'd probably make a more conscious effort to appropriately set the focal length when I am turning the camera on.

The other consideration when dealing with M lenses is to see what focal length fields are filled with what data (when not using a FF camera). Many image files will show at least 2 focal length fields. One is the actual focal length of the lens, and the other is meant to be a 35-mm equivalent focal length (to obviously be taken with a grain of salt). The exact title for that field may be reported differently as I have mostly quit looking at it. But, if you are using an APS-C camera, it very well may report 50-mm as the actual focal length at 75-mm for that equivalent length. That could be critical if you are either setting the wrong number or looking at the wrong number.

As a final note, I remember being quite fixated on that 35-mm equivalent focal length. It helped because as I transitioned from a simple P&S digital camera to a bridge type camera to a K10d, the 35-mm equivalent helped me figure out what lenses I might need. But, man it also confused a lot of things too as I was a bit ignorant on what an APS-C camera really meant and that it wasn't an FF camera (it was the same size as my old film SLR) and the whole concept of focal length was messed up until I really got a grasp on what was different (i.e. FOV). Now I've been shooting APS-C for nearly 15 years, so I've quit worrying about equivalence of anything except when I pencil out what I might need if I ever buy a K-1 (or any other FF body).
03-14-2019, 12:50 PM   #13
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As predicted, my problem, the one which caused the creation of this thread was due to Operator Error

I took the same lens, the SMC Pentax-A 50mm 1.4 back to the same location, made sure I properly set the SR to 50mm and my pp program correctly reported 50mm

thanks for all the help, suggestions and advice

Last edited by aslyfox; 03-15-2019 at 06:11 AM.
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