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08-30-2010, 01:19 PM   #1
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My New Pentax 31mm LTD...Is this normal?!

Hi guys,

I just got my Pentax 31mm a few days ago from B&H and I am already experiencing some strange behavior from the lens. I know everyone raves about how "sharp" it is from wide open so I tried to be realistic and not expect "miracles". However, even with the lower expectations I am having some difficulties. The lens does seem sharpish when you shoot close ups at F1.8 compared to landscape shots at F1.8 (as expected). However, the landscape shots are extremely soft (in my opinion). Is this normal. I uploaded some shots at the links below.

http://img842.imageshack.us/img842/8059/igp3904.jpg
http://img832.imageshack.us/img832/8545/igp3983.jpg
http://img839.imageshack.us/img839/2190/igp3987.jpg
http://img842.imageshack.us/img842/8059/igp3904.jpg
http://img826.imageshack.us/img826/94/igp3961.jpg
http://img833.imageshack.us/img833/4650/igp39612.jpg
http://img843.imageshack.us/img843/5244/igp39613.jpg

Almost all shots are focused at the center of the image ( i did not recompose ) with the exception of the house front photo (i focused at the edge where the roof meets the sky because if offered nice contrast). They are taken at ISO 200 and F1.8 and various shutter speeds. Directly extracted from Lightroom with the default sharpening removed. I dont think a focus issue is the problem as I took a bunch of landscape shots to try to convince myself that I simply wasnt focusing right and the issue seems to percist...

What made me doubt is that was this review:
Pentax FA 31mm f/1.8 AL Limited observations « robertsdonovan.com

when you look at his 100% crops of the house at 1.8, the edges seem substantially better...could those really be shots at 1.8?

Also when playing with the focus chart, I discovered that it seems like the left corners do not seem to be quite as sharp as the right ones. I have uploaded some pics of that as well.

Am I going crazy and expecting too much of this lens or is it simply a bad sample?

So at this point i am really not sure what to do...do I keep it? Do I send it back? Do I send it to Pentax for repair...?

Any advice would be extremely appreciated. Thanks in advance!

oxidized

08-30-2010, 01:21 PM   #2
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Actually, this was supposed to be the first shot. For some reason one of the link up there repeats...
http://img299.imageshack.us/img299/5426/igp4008.jpg
This is the one where the focus is on the edge between the root and the sky
08-30-2010, 02:03 PM   #3
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I think you might want to try some more shots before judging the lens. Something more on the likes of your normal photography and post some of those here.
Be aware that when you post a image for a review you want to show the best it can do, and I couldn't find a reference to pp (or lack of it) in your link.
08-30-2010, 02:17 PM   #4
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Ok I'm happy to admit I'm no expert and don't own the lense but does look fairly soft to me.

However in the EXIF I noticed a setting "Sharpness = soft (1)", is this intentional?

08-30-2010, 02:21 PM   #5
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i am sorry i dont understand whats "pp" is that post processing? There is none...

however, I did find this to be as sharp as it can be when shooting landscapes at 1.8. I really think this is the best it can do at 1.8... This did not seem to be as sharp as the ones in the review, and thats why I was asking for your opinion. I know these are not a lot of photos, but I can post more.
Here is another:
http://img685.imageshack.us/img685/6154/igp4009b.jpg
Focus was done manually on the mail box. Iso is 200, F1.8.

I admit, once you stop the lens down to say F5 it gets A LOT sharper and most landscapes I will shoot (as you say, my kind of photography) are likely to be at an even greater F stop. My only concern, as expressed in my original post, is about the sharpness at F1.8 and about the difference between the left and the right corners...Here is brick wall test at ISO 200, F1.8:
http://img521.imageshack.us/img521/2414/igp3924.jpg

I am obviously pixel-peeping, but if you look at 100% and compare the top left corner with the top right you will see what I mean. I first suspected that either the camera wasnt perfectly aligned with the wall or one of the bricks was sticking out of the wall further than the other, so I repeated it with the focus chart and a lot more precision (results are posted in my original post). Seems like the corner differance percisted.

I am only asking bcs I dont know if its a big deal or not. The edges improve a lot as you stop down, however even by F5 you can see how the left edge cannot quite catch up to the right one..
08-30-2010, 02:26 PM   #6
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Oh, I thought lightroom applies some sharpness to the raw file by default so I took the amount of sharpness under "Details" in lightroom to 0 right before I converted to JPEG. Is that appropriate?
08-30-2010, 02:47 PM   #7
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QuoteOriginally posted by kiwi_jono Quote
Ok I'm happy to admit I'm no expert and don't own the lense but does look fairly soft to me.

However in the EXIF I noticed a setting "Sharpness = soft (1)", is this intentional?
GOOD CATCH!

He has to get into the Custom Image menu settings in the camera...see which one he actually has selected...and see the 5 or six particular sub-settings for each one. (Sharpness, color saturation, etc.)
08-30-2010, 02:50 PM   #8
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QuoteOriginally posted by oxidized Quote
Oh, I thought lightroom applies some sharpness to the raw file by default so I took the amount of sharpness under "Details" in lightroom to 0 right before I converted to JPEG. Is that appropriate?
Forget about post processing for now:

Jonathan figured out your problem--your camera setting is at Soft Focus.

08-30-2010, 02:56 PM   #9
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i am sorry, i am having trouble understanding this. there is a soft focus setting?! so i have been shooting at this setting the whole time? where is it located?

I thought that when you shoot raw, camera settings dont matter. Its all just about what the sensor pics up.

Last edited by oxidized; 08-30-2010 at 03:05 PM.
08-30-2010, 03:08 PM   #10
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There is nothing wrong with the sharpen setting. Don't worry about that for now.

The focus charts look ok. The brick wall is running away to the right. Either the camera was not straight or the lens isn't. I would try again with this test.

The back porch picture is hideous. Were you using the lens hood? If you weren't, put it on and try again.
08-30-2010, 03:16 PM   #11
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I know, both the back porch and the house/mail box photos are horrible...However, this seems to be the trend from all the photos i took of objects far away at 1.8.

Btw, the lens has non-removable lens hood (not a very good one given its designed for use as 31mm) However, i am having trouble believing the issues are related just to the hood, even though it is a possibility...
08-30-2010, 03:26 PM   #12
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I disagree with the above:

For now, you should shoot JPEG only, and concentrate on getting your in-camera settings right. Although it is possible to fix many things in post processing, and many more if they're in RAW setting, you have to learn to walk before you can crawl.

And a hood has zero to do with sharp focus.

On the K-x, you have a Custom Image setting that you select. Within that main button/window, you can choose between Natural, Bright, Portrait, Landscape, Vibrant, Muted, and B&W. (I didn't check your EXIF and don't know your camera, but whatever, it's the same thing.)

These selections are set up with Pentax's defaults for the following characteristics, but you can CHANGE each one of them:

1) Saturation
2) Hue
3) High/Low Key Adjustment
4) Contrast
5) Sharpness

(The B&W selection is somewhat different, enabling you to shoot in B&W and replicating color filters.)

Basically, Pentax sets these parameters based on their best guesses of what works best for the above types of images. (Natural, Bright, Portrait, etc.)

So, you go to your Natural setting, and make sure Sharpness and Contrast are each at least one notch above neutral, so they're in the positive range. Want more? Move it more in that direction.

Natural will now always default to these settings, and your camera will always default to Natural unless you change it to Bright or one of the other selections--which again, you can modify as you see fit.
08-30-2010, 03:30 PM   #13
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I got the FA Ltd trio recently and was also disappointed with wide-open sharpness. The 31 did require some focus adjustment to be its best, but even then it's not tack sharp wide open. Same for the 43. Both are remarkably sharp from 2.8-4, though. The 77 is better.
08-30-2010, 04:27 PM   #14
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Thanks deadwolfbones. Could you please post some samples or 100% crops of yours at 1.8 and focus close to infinity just to compare.

Ira, I know what you mean. If i shoot in JPEG and adjust those settings then yes, if I push the sharpness high enough the 1.8 could be sharp. However, I think I can achive the same thing by shooting raw and then punching up the sharpness and contrast in Lightroom later.

Whats worring me is that the images that the camera produces when I shoot RAW (unsharpened and unedited) may not be as sharp as those on the internet in reviews of the lens (where they are also shot as RAW and unsharpened). If i sharpen them by the camera processor, it is like comparing apples to oranges.

This is why I was asking for the opinions of other users that happen to have the lens and whether they can confirm the issues I am experiencing...
08-30-2010, 04:35 PM   #15
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QuoteOriginally posted by oxidized Quote
. . . . . . Whats worring me is that the images that the camera produces when I shoot RAW (unsharpened and unedited) may not be as sharp as those on the internet in reviews of the lens (where they are also shot as RAW and unsharpened). . . . . . .

This is why I was asking for the opinions of other users that happen to have the lens and whether they can confirm the issues I am experiencing...
Rather than worry why not simply return the lens for another copy and check its performance. If it's better then you're home; if it's the same, then the behavior you're seeing likely is the "nature of the beast" and you can decide whether that's acceptable or not.

In my experience, B&H is exceptionally good regarding returns and makes the process pretty simple.

Jer
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