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07-03-2011, 11:36 AM   #1
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DA 35mm f/2.4 usage advice

OK, after reading the reviews of this lens and seeing a number of samples from it, I had pretty high expectations. I just got it last week and have only taken a few dozen shots with it, but I haven't been "wowed" by it yet. Most of the time, I leave my camera (K2000, Firmware 1.1.1) on "Automatic" ('cause I trust the camera more than myself to choose the right settings). I've also tried it on Av with the aperture set to f/4 and f/8 (since some reviews I've read stated that it's a bit sharper in that range). However, while many of the shots look "good", there aren't any "great" ones. Here are probably the two best examples:





These were both taken at early dusk outdoors, so maybe the light wasn't ideal. But, from everything I've read, one of the strong points of this lens is its performance in sub-par lighting conditions, and I'm not seeing that. Maybe I need to invest time in learning to manually focus and perhaps get a split prism focusing screen?

07-03-2011, 11:42 AM   #2
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Both photos appear to be out of focus, especially the second one which is pretty significantly back-focused. I think the first thing you should do is take the camera out of "Auto" mode and use the center focus point only and try to determine if you can get proper focus using AF that way. If you are still having issues, then it's possible either the lens and/or body might need an AF adjustment.
07-03-2011, 12:38 PM   #3
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QuoteOriginally posted by dgaies Quote
Both photos appear to be out of focus, especially the second one which is pretty significantly back-focused. I think the first thing you should do is take the camera out of "Auto" mode and use the center focus point only and try to determine if you can get proper focus using AF that way. If you are still having issues, then it's possible either the lens and/or body might need an AF adjustment.
I agree. Where the lens is in focus it is super-sharp, and the colours are excellent.

But this is a focus issue, so I would try exactly the advice offered above.
07-03-2011, 12:57 PM   #4
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The second image is pretty telling of a focus issue. I'd get it sent in for service work since my copy of the 35 had a front focussing issue when I first got it. Once its calibrated its a pretty impressive piece of glass for the price.

07-03-2011, 01:40 PM   #5
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QuoteOriginally posted by dgaies Quote
Both photos appear to be out of focus, especially the second one which is pretty significantly back-focused. I think the first thing you should do is take the camera out of "Auto" mode and use the center focus point only and try to determine if you can get proper focus using AF that way. If you are still having issues, then it's possible either the lens and/or body might need an AF adjustment.
Agreed. The second shot is focused on the hair - make sure you use center point focus so you know what's happening.
My copy of this lens is the sharpest lens I own, even at 2.4, and i've got a fair few reputable lenses... and auto-focus is bang on with my k-x. Really outstanding for the price.

I wouldn't be too hasty sending in for service unless you're really sure what's going on.

Here's a shot I took yesterday with this lens, and at f/2.4...




Last edited by A-z; 07-03-2011 at 02:00 PM.
07-03-2011, 01:57 PM   #6
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Yeah the second picture is definitely out of focus and the first one is a little bit out I think. However stopping it down to F8 should have enough depth to clear focusing issues. Shouldn't it?
07-03-2011, 01:59 PM   #7
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QuoteOriginally posted by epqwerty Quote
Yeah the second picture is definitely out of focus and the first one is a little bit out I think. However stopping it down to F8 should have enough depth to clear focusing issues. Shouldn't it?
It should, but 1st image is at 2.8, second is at 3.5
07-03-2011, 03:57 PM   #8
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The second image may be oof, but there is absolutely no reason to suspect a lens problem rather than simple user error - not controling the selected focus point, allowing the subject or camera to move, etc.

As for the lens being good in poor light, that just means it is *capable* of good resullts, due to its maximum aperture. But that doesn't mean it magically will produce great results with no effort. A Bosendorfer is a great piano, but it won't necessarily sound great unless played by a great musician.

07-03-2011, 07:56 PM   #9
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QuoteOriginally posted by epqwerty Quote
Yeah the second picture is definitely out of focus and the first one is a little bit out I think. However stopping it down to F8 should have enough depth to clear focusing issues. Shouldn't it?
FWIW, I don't think any lens should need to be stopped down to f8 to be sharp. It should have decent sharpness wide open and improve DOF sharpness as lens is stopped down...

QuoteOriginally posted by A-z Quote
It should, but 1st image is at 2.8, second is at 3.5
By the looks of the images, a flash was used in the 1st one (slight amount of Red Eye and shadow areas) and that would probably explain why it looks so much sharper/better than the 2nd photo...

With that in mind, if this lens can produce that image with those settings, the lens is "probably" OK and would have to agree with Marc that this maybe a case of slight user error/inexperience/PP. If it were me, use center focus and just concentrate on getting to know the lens and it's abilities. ISO 400, especially on a K2000, will produce a somewhat "soft" looking image, stick with 200 or even 100 in good/most lighting conditions.

I actually had (have) this lens in a shopping cart, ready to hit the buy button and I just happened onto this thread I read most reviews, here and on Google and found only 2 reviews discussing Auto Focus issues.
07-03-2011, 08:08 PM   #10
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QuoteOriginally posted by Marc Sabatella Quote
As for the lens being good in poor light, that just means it is *capable* of good resullts, due to its maximum aperture. But that doesn't mean it magically will produce great results with no effort. A Bosendorfer is a great piano, but it won't necessarily sound great unless played by a great musician.
Yes, I realize that regardless of the technical capabilities of a piece of gear, it's the person using it that makes the difference. So, it's clear that at the very least there is a focus issue. It would also seem apparent that the camera's choice of some parameters may not be optimal for the particular shots I'm going for.

So, auto-mode is as "right out" as counting 5 when throwing the holy hand grenade of Antioch, but for someone not experienced enough to work in complete manual mode, what would the best "next step" to take? Av mode with the aperture set to a value that provides a bit more DoF (somewhere near f/8 or f/11, maybe) to minimize the effects of the (potential) AF limitations? Maybe if that doesn't help much, more practice manual focusing?

I've gotten some very sharp photos in the past with other AF lenses. I've also gotten a few (very few) very sharp shots using MF lenses and relying on the camera's focus indicator, so I don't think there's a technical issue with the camera's focusing mechanism.
07-03-2011, 10:09 PM   #11
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I have the very similar FA 35mm f2. Test charts may show better sharpness and contrast at f8, but both these lenses are really good wide open. I generally don't bother to stop down to increase the performance of this lens.

However, you do need to fit the subject within the depth of field. See A-z's photo for a good example. The foreground is sharp, and just behind the subject the background starts to soften nicely. He says f2.4, wide open. The reason f2.4 worked for him is subject distance. Play with an online depth of field calculator at 35mm and apertures like f2.8. Vary the subject distance. At 10 feet, there's plenty of room for a person to fit within the depth of field. At 3 or 4 feet, which I'm guessing your photos were taken at, the depth of field is too small. Even with perfect focus, some part of the head is going to be out of the plane of sharp focus. Maybe OK but maybe not.

One quick fix - back up a few feet, then crop later. But it's not ideal.

I really like Av mode because of the control over depth of field. Shutter speed just needs to be good enough to eliminate shake. Adjusting one thing is easier on a single-dial camera too. There is a learning curve but with a prime lens, the variables are limited. If you can get a test person to sit still for a while in daylight, you can take practice shots at different distances and apertures.
07-03-2011, 10:36 PM   #12
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Both shots are back focused, now you must figure out if this is due to incorrect AF point selection by camera, or it really is a combo of lens & body causing back focus.

So step one is set centre point only and try some more pics ensuring what you want to be in focus is dead centre when you half press the shutter.

If that doesn't solve it then confirm BF by shooting a test chart.

If you find a case of BF then you need to contact Pentax and arrange for the lens to be calibrated. It's worth it because in my view the lens is not usable if it's back focusing by the amount it appears to be in your pics.
07-04-2011, 08:18 PM   #13
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I have it and like it (the lens)

Yeah it's just the focus that's a bit off in these pics just as everyone else says. contributing to this is that the camera is pretty near to the subject, its a large aperture and it's 35 mm. i have this lens and i think its wonderful especially for the price. children are known for moving around a lot and just a few inches is absolutely enough in this case to make the camera lose focus. you could try to switch to continuous autofocus for instance if its possible (i have a k20d where you can with switch) but it will never be perfect. i guess we pentaxians love our little babies for their flaws as well as their perks. pentax as a brand is known for a bit slow autofocus compared to c & n but hey, that's the charm! you have to be a better photographer to use pentax than canon or nikon! besides it's not about perfect focus anyway and never has been (at least not in the kind of photography I love). the chaos and chance of photography is the charm of it. a picture will never be EXCACTLY as you want it to be...
sorry about the lecture, i'm actually sort of a dslr beginner myself ...
having said everything everyone else already said. here is where i retire and acknowledge that this is just one of my two replies to be allowed to buy lenses in the shop
p.s. this lens is sharp, good colors, fast autofocus etc just a bit plasticky but hey. thats the charm! d.s.
07-04-2011, 09:40 PM   #14
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QuoteOriginally posted by wedge Quote
So, auto-mode is as "right out" as counting 5 when throwing the holy hand grenade of Antioch, but for someone not experienced enough to work in complete manual mode, what would the best "next step" to take? Av mode with the aperture set to a value that provides a bit more DoF (somewhere near f/8 or f/11, maybe) to minimize the effects of the (potential) AF limitations?
AV mode is fine; it lets you pick the best aperture for the particular shot. But if it's always it's always a matter of you picking f/8 or f/11 just to get more DOF to cover a failure to focus carefully, you aren't likely to get results that are any different from the kit lens, which is excellent at that focal length and aperture as well. And of course, f/8 is of no use at all in low light,, so it kind of negates the purpose of having bought the lens.

So I'd say, step one, learn to focus carefully - which basically means, practice selecting fopcus points, aiming that at appropriate parts of the subject where the camera can't also see something in the background or foregound. Step two, practice shooting at different apertures to learn what the DOF actually looks like. And start making a note of what kind of shutter speeds you can get at different ISO levels in different types of light, so you will have realistic expectations and understand you will be forced to use a larger aperture for shutter speed reasons than you might prefer for DOF reasons. This is all a matter of experience.

> Maybe if that doesn't help much, more practice manual focusing?

That's a good idea too too.
07-05-2011, 04:22 PM   #15
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Focus issue.
First one is focused on the hem of the left sleeve so definitely not back focused and the 2nd is focused on the strap which is back focused.
It might be the issue of the focus points too, letting the camera choose the focus points really doesn't give you too much control on what you need to focus on.
Auto everything will not really yield great results, not unless you know what you are doing too. So, even at "auto" there are certain things that you should be aware of..like what the camera chose to focus on, what aperture opening it chose and what speed it chose..including what ISO it chose.
Using one of the modes is also like "auto" only that you get to control one aspect then either you let the camera choose the other stuff like ISO setting or you set it yourself.
If you use Av, the Tv "automatically"adjusts to your chosen opening.
If you use Tv, the Av is "auto" chosen for you.
If you want to set the camera to choose the ISO, then it can also do that in a certain range you set like 100-1600 ISO.
Manual mode is I would suggest you keep out of, since that would be mixing all of the above parameters to achieve the "look" that you want which the camera can never give you automatically.
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