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Yellowed Super Takumar 50mm f/1.4 - How sharp?
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PostPosted: Mon Oct 01, 2012 9:35 pm    Post subject: Yellowed Super Takumar 50mm f/1.4 - How sharp? Reply with quote

Hi!

I have just bought a 50mm super-tak (not smc) and as I had imagined it is totally yellowed. This does not worry me a bit: I am ready to give my lens some good winter tanning. What worries me is the lens not really being tack (or tak) sharp, even when I shoot B&W. Specially when my focus is on a distant subject, the IQ is really mediocre, regardless of the lighting condition and the aperture value. Now my main question is whether I have to keep this lens or send it back. Underlying this question, there are four questions:

1) Does the characteristic Tak yellowing cause diffraction, resulting in low IQ? If you have deyellowed your copy, have you noticed any significant improvement in IQ?
2) This is a 33xxxxx series supertak and it goes up to f/16. Is there anything I should know about this particular copy I have?
3) I use a generic mount converter. Can this be a simple shimming issue?
4) I am using the lens on a 400D with no sensor fine-tuning. Is it possible that I get different results on a more modern camera that can adjust to lens peculiarities?

Any comment is appreciated. Smile


PostPosted: Mon Oct 01, 2012 9:45 pm    Post subject: Reply with quote

Some questions -

- When you shoot infinity, what aperture are you using ? This lens should be as sharp as anything out there at f/5.6
- Did you bracket focus ? On an adapter do not trust the infinity mark. It takes just a bit to be a little out of focus.
- Did you try the infinity focus test with another 50mm lens ?
- Did you check for haze, separation or other issues ?

As for the effect of being yellow - I haven't seen any change in quality yellow or not.


PostPosted: Mon Oct 01, 2012 11:06 pm    Post subject: Reply with quote

luisalegria wrote:
Some questions -

- When you shoot infinity, what aperture are you using ? This lens should be as sharp as anything out there at f/5.6
- Did you bracket focus ? On an adapter do not trust the infinity mark. It takes just a bit to be a little out of focus.
- Did you try the infinity focus test with another 50mm lens ?
- Did you check for haze, separation or other issues ?

As for the effect of being yellow - I haven't seen any change in quality yellow or not.


The same here: I had some copies of this lens, and the only real problem of the (badly) yellowed ones was that they were slightly darker at same aperture than other lenses/other non yellowed takumar.


PostPosted: Mon Oct 01, 2012 11:15 pm    Post subject: Reply with quote

Yellowing issue not effect sharpness, if you have sharpness issue , check your adapter first, may need to shim a bit. Don't test sharpenss at infinity less than f5.6-F8. If still unsharp at F8, either need to adjust lens or replace adapter.


PostPosted: Tue Oct 02, 2012 2:10 am    Post subject: Reply with quote

Take a few shots wide open near infinity(start at infinity stop, then small movements between pictures) if you don't have a shot with decently sharp focus at infinity, there is a possibility the adapter is too thick, or the lens was previously adjusted for infinity with an adapter that was too thin, either way infinity focus will not be good.
To see how sharp it should be, take some shots at a closer distance, 3' to 20' is good.

Feel free to post some shots, not everyone's opinion on what is sharp is the same.

To give you an idea of how sharp, this is taken with the early 8 element version wide open.


PostPosted: Tue Oct 02, 2012 2:54 am    Post subject: Reply with quote

Shhh don't tell anyone how good they are..

This was either shot at f1.4 or f2. The exif reads iso400, s=1/4th 9:05pm

The original jpg looked like this.

This was the construction site at Hammer Hall in Melbourne before they had finished it all. the BW edit removes my shit attempt of exposure, and I like the image mirrored.

Just take pictures with the dam thing and do not, I repeat, do not tie yourself in circles caring about lines per millionth of a bees dick Razz


PostPosted: Tue Oct 02, 2012 12:22 pm    Post subject: Re: Yellowed Super Takumar 50mm f/1.4 - How sharp? Reply with quote

Retrography wrote:

1) Does the characteristic Tak yellowing cause diffraction, resulting in low IQ? If you have deyellowed your copy, have you noticed any significant improvement in IQ?

Yellowing does not cause diffraction. It's only like a yellow filter. Influence of the coloring in sharpness should be only very low.
Quote:
3) I use a generic mount converter. Can this be a simple shimming issue?

Does the adapter contain glas? If yes yes. If not simply shoot @ ~F2 straight on a wall and look on computer if the field of sharpness is uneven.
Quote:
4) I am using the lens on a 400D with no sensor fine-tuning. Is it possible that I get different results on a more modern camera that can adjust to lens peculiarities?

There are differences but that would'nt make look a sharp lens soft in center.

I guess your copy only has a decentered glas element


PostPosted: Tue Oct 02, 2012 6:58 pm    Post subject: Reply with quote

Thanks for all the responses. I take it out today for some test shots. I understand that adapter may be at cause. Maybe I can test another one. I will post my shots later on.

Thanks again!


PostPosted: Tue Oct 02, 2012 8:11 pm    Post subject: Reply with quote

Before going out I took some shots from the balcony. On all of them the best view through viewfinder concurred with the camera's focus confirmation beep. Please let me know what you think about them.

Wide Open, 10m distance, focus on the pink stone:



100% Crop:




@f/1.8 (or 2), 10m distance, focus on the pink stone:



100% Crop:



@f/5.6, 10m distance, focus on the pink stone:



100% Crop (center):



100% Crop (top):



@f/5.6, infinity focus (end of the ring):



100% Crop:




Am I too demanding, or there is really something wrong with this lens?


PostPosted: Tue Oct 02, 2012 8:36 pm    Post subject: Reply with quote

Out of focus I think. I get much sharper results. You could have a misaligned element or group also; sometimes the front or rear group may not be screwed all the way in, etc., but I would test more to be sure.
Don't depend on the focus confirm beep, these things are too imprecise.

Try this - find a subject with a lot of detail, and shoot it at an angle, so some of it is guaranteed to be in focus. If its all bad, then you have a lens problem.

Whats your camera ?


PostPosted: Tue Oct 02, 2012 8:43 pm    Post subject: Reply with quote

looking at that i think this has been opened up and one of the elements is flipped

Take a look here at the diagram i would guess that the last element has been flipped near to sensor
http://www.pentaxforums.com/lensreviews/SMC-S-M-C-Super-Takumar-50mm-F1.4.html

normally can be undone by hand to change around
Show us a pic of the rear element from a side view and on top
The supertak should be almost flat on rear element


Last edited by eddieitman on Tue Oct 02, 2012 9:08 pm; edited 2 times in total


PostPosted: Tue Oct 02, 2012 9:07 pm    Post subject: Reply with quote

My camera is a canon 400d. I get much sharper photos with my efs 17-55 f/2.8. I have already tried shooting patterned surfaces, but all seems to be blurry anyway, even where the image is the sharpest. I guess I have a lens issue then...


PostPosted: Wed Oct 03, 2012 12:34 am    Post subject: Reply with quote

I was thinking that there was some back focus, which means that the focus screen and sensor are at different distances from the lens, and the only cure is to shim the focus screen.
Try this:
Get a piece of paper with writing on it, set it at on the ground in front of you so the writing starts out far from you and gets closer, now pick a line that is easy to find, and focus on that line(wide open) and take a picture(also wide open), now look at your picture, is the plane of focus on that line or has it moved?

You are simulating this test:


A link to a test image that you can print if you feel like it, though all you need is some news print.
http://fotograpr.com/download-lens-back-focus-test-sheet.html


PostPosted: Wed Oct 03, 2012 12:42 am    Post subject: Reply with quote

Thats exactly the proper test to exclude focus problems.

In this case though it seems the lens already failed this test.


PostPosted: Wed Oct 03, 2012 1:16 am    Post subject: Reply with quote

Your f1.8/f2 image looks like the center is not sharp, but there is a sharper region to the top right side? I say one or more of the elements are misaligned.


PostPosted: Wed Oct 03, 2012 6:31 am    Post subject: Reply with quote

aleksanderpolo wrote:
Your f1.8/f2 image looks like the center is not sharp, but there is a sharper region to the top right side? I say one or more of the elements are misaligned.

Which could be explained by back focus, a few tests should be able to sort out where the problem is.
misaligned elements would show up in a brick wall test shot.
The first thing to do is find out if focusing with the OVF is accurate.


PostPosted: Wed Oct 03, 2012 6:51 pm    Post subject: Reply with quote

My experiences....

Attempting to focus with wider than F4 is not an option with a 400D
Focus chips are pretty unreliable
The 50/1.4 is not very sharp wide open


PostPosted: Wed Oct 03, 2012 7:04 pm    Post subject: Reply with quote

Even with f/1.4 it should be much, much sharper than the samples shown here.
If there isn't a focus problem then it is certainly a faulty lens.


PostPosted: Thu Oct 04, 2012 4:56 am    Post subject: something is very wrong with the lens Reply with quote

I have shot with many 50mm takumars over the years and none looked as bad as these samples.
Reject the lens, there is something very wrong with it.


PostPosted: Thu Oct 04, 2012 5:07 am    Post subject: Reply with quote

I just sent my copy to a guy in Tennessee for repair. He's exceedingly good and thorough. If you want his website, send me a PM. My copy's repair was $38, but the problem was oil on the blades. Part of the standard lens repair includes focus verification.

The Takumar 50mm 1:1.4 is definitely worth having professionally serviced.


PostPosted: Thu Oct 04, 2012 2:49 pm    Post subject: Reply with quote

luisalegria wrote:
Even with f/1.4 it should be much, much sharper than the samples shown here.
If there isn't a focus problem then it is certainly a faulty lens.

+1


PostPosted: Fri Oct 05, 2012 3:25 pm    Post subject: Reply with quote

Hello Again!

LightShow has mentioned it may be a backfocus problem. I sincerely doubt. I have tested for this by taking pictures of surfaces with complex patterns. The problem is not that the part I am focusing on is not sharp, but rather that wherever the sharpest point in the photo is, it is not sharp enough yet. The performance is somehow variable, sometimes better and sometimes worse, but in all cases the results are much worse than my non-L canon zoom lenses (that I do not consider as particularly sharp).

eddieitman has mentioned that the rear element might be flipped. This can be the case, but I can not check it through the flatness test that you have suggested. First of all my rear element is already flat, and second, it seems that both sides of that elements are as flat, so, even if it is flipped I cannot detect it.

aleksansderpolo has suggested that one of the elements might be misaligned. I think this is probably the case. One of the elements is both misaligned and flipped I think. If this was some less complicated lens that I had some experience with I would have opened and checked it, but I don't know SuperTaks enough to do so on my own.

David has suggested that I send the lens to his trusted repairman in Tennessee. Probably if I can't return the lens, I will do so. It is just that I live up here in Montreal and the shipping cost will probably exceed the total price of the lens including the CLA!

Sincerely, this lens is so gorgeous on my camera I don't like to return it, and seems very well kept over years. I just don't know how the previous owner has managed to do this to it. If I you know of an affordable CLA option around me in MTL, I will readily consider it!

Thanks everybody...


PostPosted: Fri Oct 05, 2012 3:28 pm    Post subject: Reply with quote

I think that your test images are back-focused.