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07-16-2011, 12:51 PM   #1
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Focal length input for M 75-150mm f4 - Actual experiences

"Bonjour",

I have read the previous threads, but does anyone have any actual experience dialing in differing "focal length inputs" for a M 75-150 f4 lens? I just bought one out of the UK and have just started testing it.

The previous threads have a lot of suggestions, but I would prefer some advice for this specific lens. Thanks in advance for any feedback of your experience.

"Salut & bonne journée, Jean"


Last edited by Jean Poitiers; 07-18-2011 at 03:41 AM.
07-16-2011, 12:59 PM   #2
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Sorry, only with the K45-125/4 myself. When I dial in a mid-range # it seems to do just fine across its range. Good luck with specifics on the M75-150.
07-16-2011, 01:55 PM   #3
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Merci Docrwm ... Just FYI, before reading the previous threads, I was putting in "150" and getting very good results. Now I am going to step-down the a mid-point of "100", like you suggested, and see the results ... and then step-down again to "75" and compare all.
07-16-2011, 02:34 PM   #4
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QuoteOriginally posted by John Poitiers Quote
Merci Docrwm ... Just FYI, before reading the previous threads, I was putting in "150" and getting very good results. Now I am going to step-down the a mid-point of "100", like you suggested, and see the results ... and then step-down again to "75" and compare all.
Ce n'était rien. Je me réjouis de votre rapport des résultats.

De mon mieux,

-Robert

S'il vous plaît excuser mon mauvais Français incroyablement.

07-16-2011, 04:56 PM   #5
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QuoteOriginally posted by John Poitiers Quote
Merci Docrwm ... Just FYI, before reading the previous threads, I was putting in "150" and getting very good results. Now I am going to step-down the a mid-point of "100", like you suggested, and see the results ... and then step-down again to "75" and compare all.
I will be glad to see your results.

In theory, anti-shake correction error is proportional to focal length error.

If you know what focal length you will use, that's what you should tell the camera.

If you don't know what focal length you will use I think you should tell the camera the average focal length - in this case (75+150)/2 ~ 100 this should minimize your mean square error.

The above is true for normal photography; for macro photography multiply focal length by (1+magnification).
07-16-2011, 09:56 PM   #6
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Hi folks! I think you need to take a look here:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/132496-shake-reduc...ll-time-2.html

Actually, since the M75-150/4 has only a 2:1 zoom range, you can't go too far wrong with this lens, but you'll definitely get best all-round results by setting the value to 100mm. Actually, 100mm turns out to be the best for the other common tele-zooms of that era, i.e. the 70-210s, 80-200s etc.

If you do use a value of 100mm for the 75-150/4, worst-case SR performance (i.e. with the zoom set to min or max FL) still results in a blur reduction down to 1/3 of what you would have got with SR turned off.

Worst setting is the maximum zoom value when you actually have the zoom set to minimum FL.
07-17-2011, 11:25 PM   #7
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By the way, I've owned one of these lenses for over 30 years, and I can report that it offers very good sharpness. Focus it accurately (do not rely on the camera's focus indicator!) and you'll be pleased with the results.

One thing: in common with most Pentax lenses from this era, it is rather subdued at the red end of the spectrum. If there's not much red in the image, this won't matter, but if there is a significant amount of red, the effect is to give the image a rather cool appearance which is slightly lacking in contrast. For best results, correct this in PP.
07-18-2011, 01:57 PM   #8
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Merci à tous ...

Bonjour,

Thanks everyone for your comments and input ... it really helps a lot.

à DocRwm: Mon français est nul aussi, donc il faut pas s'excuser. C'est pas grave de faire des fautes ... surtout pour nous, les 'ricans!

à newarts: "Merci" - I'll post some photos later if time allows - maybe only the best ones and a few comparative shots as well ... "on verra"

à m42man: Thanks for your link ... didn't see that specific one, but did stumble upon Falk Lumo's chart(s). I am really excited to have found my 75-150 f4, and it's great to hear that it's "good" like you and this forum's users have stated ... I kind of based my purchase decision in part on their reviews. Do you have suggestions for another manual zoom ... or maybe a short fix (I'm looking first for a M or A 50mm f1.7 or faster, then maybe a 28mm).

"Allez, merci encore et bonne journée, Jean"

07-18-2011, 05:13 PM   #9
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QuoteOriginally posted by John Poitiers Quote
Bonjour,

Thanks everyone for your comments and input ... it really helps a lot.

à DocRwm: Mon français est nul aussi, donc il faut pas s'excuser. C'est pas grave de faire des fautes ... surtout pour nous, les 'ricans!

.........................
"Allez, merci encore et bonne journée, Jean"
Merci, étant donné votre emplacement je pensais Français était langue de votre choix. Il est bon de pratiquer si.
07-18-2011, 11:24 PM   #10
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QuoteOriginally posted by John Poitiers Quote
à m42man: Thanks for your link ... didn't see that specific one, but did stumble upon Falk Lumo's chart(s). I am really excited to have found my 75-150 f4, and it's great to hear that it's "good" like you and this forum's users have stated ... I kind of based my purchase decision in part on their reviews. Do you have suggestions for another manual zoom ... or maybe a short fix (I'm looking first for a M or A 50mm f1.7 or faster, then maybe a 28mm).
Pleased to be of help!

I can't offer much by way of recommendation regarding zooms (the M75-150 is the only manual zoom I have), but I can say there are plenty of nice 50s, 35s and 28s out there (especially if you're willing to consider M42 lenses):

You've mentioned the Pentax 50/1.4 and 50/1.7. You could also consider the S-M-C Takumar 55/2 and Rikenon 50/2 (very sharp, very cheap, probably best to avoid the -P version).

For 35s, look at the S-M-C Takumar and rarer Pentax "K"s. Highly recommended!

For 28s, go for the Vivitar Close Focus (Komine f2 and f2.8 versions, identified by serial numbers starting with "28"). Again, highly recommended (though I unfortunately don't own one that is mountable on my camera - yet!).

Happy hunting!
07-24-2011, 12:38 PM   #11
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QuoteOriginally posted by m42man Quote
Pleased to be of help!

You've mentioned the Pentax 50/1.4 and 50/1.7. You could also consider the S-M-C Takumar 55/2 and Rikenon 50/2 (very sharp, very cheap, probably best to avoid the -P version).

For 35s, look at the S-M-C Takumar and rarer Pentax "K"s. Highly recommended!

For 28s, go for the Vivitar Close Focus (Komine f2 and f2.8 versions, identified by serial numbers starting with "28"). Again, highly recommended (though I unfortunately don't own one that is mountable on my camera - yet!).

Happy hunting!
à m42man, Merci beaucoup! Thanks for your advice ... I will do some happy hunting soon, and M42 lens will now be on my shopping list(s), too. A+, John
07-24-2011, 01:05 PM   #12
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Some quick shots with M 75-150 f4

Re-Bonjour,

Update: I haven't had much time to test formally, but a few "off the hip" shots seem to show that a "100mm" focal input works quite well.

Attached are two shots: one in my office before heading off to lunch ... focused on the brim area of the coffee mug at about 4 feet, 100mm input with SR, flash at "-2", ISO 200, 1/180, f11(?), etc. Yes, I should be taking better notes here, but what I like is the sharpness ... the grain of the mini-rugby ball and actually seeing the thickness of the paint on the mug. The 11 Mo original of this photo is much better.

The second shot is my ad hoc stained glass window test at "Notre Dame la Grande" while heading off to get a sandwich ... hand-held at f8(?), 100mm input w/SR, no flash, ISO 400, 1/250, at 30+ feet, etc. Lots of good detail across the frame, much of which is lesser in the 1 Mo format.

I really think that I'm going to love this lens ... more later when time allows.

A+ (= short for "à plus tard"), John
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07-24-2011, 01:50 PM   #13
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What a lovely shot of the stained glass! I'm glad you like the lens, that is a great shot. I love shooting stained glass, and you have some genuinely great ones it seems available to you.
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