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08-09-2008, 09:27 PM   #1
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Takumar 50mm F1.4 low contrast at narrow F-stops

I just picked up a Super-Multi-Coated Takumar 50mm F1.4. Of course, it is a screwmount, so I had to get an adapter to use it on my K10D. I took it out for its first real day of shooting today, and I'm not as impressed as I thought I would be, given the fantastic reputation of this lens.

In particular, I notice that the color representation and contrast are fine at wide apertures, but the color is blah, and the contrast week beyond about 5.6.

The thumbnails below will all open in a seperate window

Tree at F 1.4:


Same tree at F 8.0:


Little League Field at F 4.0:


Same Little League Field at F 8.0:


Pond at F 4.0:


Same Pond at F 16:


I know there are a lot of users of this forum that swear by the Takumar F1.4 normal lens, so I was surprised by this lackluster performance at slow F-stops. Has anyone else seen anything like this?

Thanks.

08-09-2008, 09:30 PM   #2
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I should have added this note: I shot in Manual mode at ISO 100. I set the F stop and then pressed the green button to get the shutter speed and fired. I shot in highest quality JPEG format.
08-09-2008, 09:40 PM   #3
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QuoteOriginally posted by Slowpoke Rodriguez Quote
I should have added this note: I shot in Manual mode at ISO 100. I set the F stop and then pressed the green button to get the shutter speed and fired. I shot in highest quality JPEG format.

Hmm, not my experience at all... Does the lens have fungus, or any cleaning marks on the elements? looks like you're getting a lot of diffused flare, cutting down the contrast.
08-09-2008, 10:28 PM   #4
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looks like the stopped down photos are a bit overexposed
the metering w/ old lenses is kind of iffy and so you might want to check both photos have the same exposure?

08-10-2008, 12:15 AM   #5
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QuoteOriginally posted by k100d Quote
looks like the stopped down photos are a bit overexposed
the metering w/ old lenses is kind of iffy and so you might want to check both photos have the same exposure?
This appears to be part of what's going on. For instance the exif on the first tree:

f/1.4 (reported) has speed: 1/3000th
f/8.0 (reported) has speed 1/60th

Correct me if I'm wrong, but:

From f/1.4 to f/8 is a 5 stop difference. Calculated exposure equivalence from the f/1.4 base would be to move to 1/100th, representing about a half stop (over)exposure gain.

And the last pond photo:

f/4 @ 1/750th
f/16 @ 1/20th

f/4-->f/16 represents a 4 stop difference
1/750th --> 1/20th represents about 5 stops... again, possibly towards overexposure on the f/16 shot. That would be 1 stop overexposure.


So it looks like an exposure problem. I'm not sure that is the only problem, but it seem that it could be a factor.

Frank.
08-10-2008, 12:44 AM   #6
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The truth. The more closed down the lens is, the more you will overexpose it using the metering. This is where your M skills come in handy Compensate it.

Do you use a hood?
08-10-2008, 09:33 AM   #7
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I must give credit where credit is due and I believe that k100d and Frank Fletcher have hit this on the head. I will take Frank's work a little further.

The tree photos:
At F1.4 and 1/3000 second and ISO 100, the EV is 12.5
At F8.0 and 1/60 second and ISO 100, the EV is 11.9

The ball field:
At F4.0 and 1/500 second and ISO 100, the EV is 13.0
At F8.0 and 1/60 second and ISO 100, the EV is 11.9

The pond:
At F4.0 and 1/750 second and ISO 100, the EV is 13.6
At F16 and 1/20 second and ISO 100, the EV is 12.3

Gentlemen, we have a trend. At narrower apertures the camera's meter is seeing the scene as darker, hence the lower EV readings. Because of this, it is keeping the shutter open longer to allow in more light to compensate for its erroneously low EV reading. This is why the stopped down pictures look over-exposed. They are. Good detective work, fellas.

Now, some more food for thought. I also had my SMC-M 50mm F1.7 lens with me that day for a photo comparison, and the shots at narrow apertures with the M lens did not overexpose. Although maybe ten years newer, the M lens is manual everything just like the Takumar. I wouldn't think there is any technological advantage for the M lens (i.e., it isn't talking to the camera body any more than the Takumar is). So, could it be that the yellowing that the Tak exhibits, and the M doesn't, is throwing off the meter? In theory, and I'm not an expert, this makes sense. The yellowing of the lens elements could act like sunglasses on the glass which would make the camera think it is darker out than it really is, which would cause the camera to over-expose the pictures. Maybe at wide open F-stops it gets enough light to meter correctly even with the yellowing, but at narrow F-stops it doesn't. I'll post pics of the lenses.



08-10-2008, 03:00 PM   #8
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technically the metering should be the same stop-down metering between the takumar and M. good luck finding the solution . otherwise only testing will help you to determine the correct exposure compensation, let us know what you find.

08-11-2008, 11:18 AM   #9
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Slowpoke, your experience is consistent with mine, and I agree that it's overexposure.

I just spent some time in Nevada's Red Rock Canyon with my Super Tak 135 f/2.5, which needed to be stopped down quite a bit in the harsh midday summer desert sun.

I didn't really notice too much until I got the pictures on my PC (hey, it's really hard to use the LCD for anything other than a quick after-the-fact focus check when it's that bright), but a lot of my pictures ended up kind of washed-out looking, like your samples. The few times I got good contrast and colors, I used faster shutter speed by 1 or 2 EV beyond what the green button suggested -- quite a bit!

Lesson learned! I'm a novice and learning every day, so I don't mind. Plus, I shot in RAW so I can fix up the overexposures quite a bit, I'm sure. They're not really blown out, just hazy looking.
08-12-2008, 10:49 PM   #10
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QuoteOriginally posted by Zewrak Quote
The truth. The more closed down the lens is, the more you will overexpose it using the metering.
I was intrigued by this comment because I didn't think that I noticed the same thing with the M lens as I did the Takumar. They are both manual lenses, so I should see the same effect. So, a little more testing was in order.

I took some pictures in a controlled environment (I don't have to worry about whether it was a little cloudier when such and such lens was on). Just some shots of a wall lamp. I aimed the lens right at the same middle point of the lamp for every picture. Same as before, I set the ISO to 100 for all shots, I set the aperture, and pressed the green button for the shutter speed. In all cases I used what the camera suggested for the shutter speed. I will show my calculated Exposure Value for each picture.

With the Super-Multi-Coated Takumar 50mm F1.4 lens:


F=1.4, Shutter = 1/3000 sec., Exposure Value = 12.5


F=4.0, Shutter = 1/350 sec., Exposure Value = 12.5


F=8.0, Shutter = 1/45 sec., Exposure Value = 11.5


F=16, Shutter = 1/8 sec., Exposure Value = 11.0

These findings are consistent with my outdoor shots in the original post. As the Aperture narrows, the camera's meter reads less available light and changes the shutter speed. Ideally, the Exposure Value would not budge, because I know the lamp isn't suddenly giving off more light.

With the SMC Pentax-M 50mm F1.7 lens:


F=1.7, Shutter = 1/3000 sec., Exposure Value = 13.1


F=4.0, Shutter = 1/350 sec., Exposure Value = 12.5


F=8.0, Shutter = 1/45 sec., Exposure Value = 11.5


F=16, Shutter = 1/8 sec., Exposure Value = 11.0

I see precisely the same phenomenon with the M as I did the Takumar. As the F stop narrows the camera starts metering for less available light, the EV goes down, the shutter is held open longer than it should be, and the picture is brighter than the pictures at wide apertures. Again, the subject hasn't changed at all. The EV readings should be the same. If 13 is correct at F1.7, then 13 should be correct at F16. This means my observation that I was only seeing this phenomenon with the Takumar and not the -M lens was incorrect. In fact, the effect is greater with the -M lens. A swing of 2 EV units is shown for the -M and a swing of 1.5 units is shown for the Tak. Zewrak was correct. Gotta give credit where credit is due.

To round out the picture here I decided to see if I see the same phenomenon for lenses that can talk to the camera body. I put on my FA 35mm lens and did the same test. Results below.

With the SMC Pentax-FA 35mm F2.0 lens:


F=2.0, Shutter = 1/750 sec., Exposure Value = 11.6


F=4.0, Shutter = 1/180 sec., Exposure Value = 11.5


F=8.0, Shutter = 1/45 sec., Exposure Value = 11.5


F=16, Shutter = 1/10 sec., Exposure Value = 11.3

And now some more examples with the FA 35 using sunlight, not lamplight.


F=2.0, Shutter = 1/20 sec., Exposure Value = 6.3


F=4.0, Shutter = 1/6 sec., Exposure Value = 6.6


F=8.0, Shutter = 0.7 sec., Exposure Value = 6.5


F=16, Shutter = 3 seconds, Exposure Value = 6.4

With the -FA lens on, the K10D's meter is consistent throughout the F-stop range. In both artificial and natural lighting scenerios, the metering discrepency is not more than 0.3 EV units. That is very good, considering that not all EV scores are even possible (meaning, the camera can't decide to hold the shutter open for 1/49th of a second, even if that would be perfect). For this reason, I believe that it is metering as consistently as possible with the -FA lens.

My Conclusion:

When the lens and the K10D can't talk, the camera's meter has a consistent tendency to overexpose images at narrow apertures. I've seen this with two different lenses and in two different lighting scenerios: artificial (this post) and natural (the original post). The swing can be pretty dramatic too, ranging as high as two full exposure value units (2 stops in traditional parlance). However, it appears that this isn't a problem when the lens and camera body can talk. I've only tested this so far with my -FA 35mm, so I'm not as confident of this finding, but it certainly holds true for this lens. When I get a chance I may give this kind of a test to some other auto exposure capable lenses.

I hope people find this interesting. I like it. And thanks again, Zewrak
08-12-2008, 11:06 PM   #11
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I get much more acurate readings with my takumar lenses and K10D while shooting Av mode, not manual and then compensate from there if I have to.
08-12-2008, 11:43 PM   #12
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Now try it with the different meterings. I think, but I am not sure, that your results might be slightly better with weighted, if you used spot in your test.

This is not a big deal really, I just use EV compensation. By the way, have you tried "auto compensation"? I never did. I think its easy to just raise the compensation, the more I close the lens down.
11-28-2008, 12:59 AM   #13
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Hello everybody

I am having same problem, but when i use my Nikon 50mm f1.4 it is fine so i can't see how it is a meter issue
11-28-2008, 11:42 AM   #14
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The metering issue with pre A lenses is well documented for the K10D. The general consensus is that the brighter focusing screens Pentax used from the K10D onwards throw off metering with older lenses.

Apparently, the focusing screen from the *ist series will resolve the metering errors in the K10D.

M-lens metering with K10D redux

And here's a picture showing the over/under exposure that Godfrey posted in that thread:

http://homepage.mac.com/godders/mCAL/calibration-K10.jpg
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