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04-07-2020, 05:55 PM   #1
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Pentax K-70 soft image issues

Hi,

I hope someone is able help me with this. I always feel that images taken with the k-70 are quite soft, not very sharp at all. I've tried various f stops, shutter speeds and ISO range and nothing seems to make a difference. I'm going to attach of photo of my son so that you can see what i mean. It was shot at f/3.5 1/400 at ISO 500.


Any ideas or help would be appreciated.


Thanks

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PENTAX K-70  Photo     

Last edited by scottish_explorer; 04-09-2020 at 07:10 PM.
04-07-2020, 06:12 PM - 1 Like   #2
pjv
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I think your issue is related to your lens. The reviews on the forums here are worth reading IMO. Good luck.

Tamron 28-75mm F2.8 AF XR Di LD Macro SP Lens Reviews - Tamron Lenses - Pentax Lens Review Database
04-07-2020, 08:12 PM - 1 Like   #3
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I would check your camera/lens for front-focus or back-focus with a static subject.
04-08-2020, 12:19 PM   #4
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+1 @pjv in that it's mostly the lens in combination with the long end of the focal length of a zoom and the large f/3.5 aperture. There are much sharper zooms in the 75mm range and any prime which will get your sharper results.

04-08-2020, 08:17 PM   #5
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Your photo is quite dark, under-exposed. This is one factor detracting from perceived sharpness. Also, set your camera's AF to AF-S, then set for center-only AF point for spot-focus, then use the shutter button half press to establish focus on the eye. Hold that half press to hold focus, reposition the camera for framing and complete your shot. Also, use a little pop of fill flash, even in daylight for outdoor people shots, to fill in shadows and put a bit of catchlight in the eyes. If you wanted the background to be dark like it is, then set your exposure accordingly, then the fill flash would have brightened his face. You can adjust the flash output. A separate flash unit in the hot shoe is preferred, especially with a large lens like the one you are using. However, if in daylight bright enough, you might get away just fine using the built-in flash. Red eye would not be a problem, and any shadow in the lower part of the frame cast by the large lens may not be noticeable- just remove the lens hood.

You really do not need 1/400 sec for fine results in shooting photos of a person just standing there. The upper normal flash sync with the K-70 is probably 1/180 sec which is plenty. In fact, you might be able to reduce your ISO, depending on how bright the day is. Take readings of the background without your subject first to get an idea of optimum exposure without the flash operational, and then be sure shutter speed does not exceed 1/180 sec. You can go as low as 1/125 sec or even a bit lower for a still person. You can keep your aperture to f/3.5 if that blurs your background well, as it has in your sample photo, manipulating exposure also by using the ISO setting.

Last edited by mikesbike; 04-09-2020 at 03:46 PM.
04-09-2020, 07:45 AM - 1 Like   #6
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It's difficult to say just with only this picture. As others said, it could be a back or front focus issue, but it also could be a misfocus. Unfortunately the data about how the picture was focused are missing in the exif. So, it's hard to tell... You could make a few test pictures using Liveview. If the softness disappear it would strongly suggest a focus issue. On a portrait like this, at 70mm f3.5, there's about 6 inches of DOF and even a slight misfocus could make the picture appears softer than it should be...


As said above, the lens is at its worst: longest end and almost fully open. So, some softness might just be normal with this lens under these conditions... What about other focal length ? Are the pictures still soft at 50mm f5.6 ?
04-09-2020, 07:07 PM   #7
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Yeah, the photo is underexposed and that will contribute to the problem.
Even when I have proper exposure and with a different lens I feel the images just aren't very sharp.

I'll add a few pics here for you to see.

I may well be over compensating with 1/400, I have shaky hand lol.

QuoteOriginally posted by mikesbike Quote
Your photo is quite dark, under-exposed. This is one factor detracting from perceived sharpness. Also, set your camera's AF to AF-S, then set for center-only AF point for spot-focus, then use the shutter button half press to establish focus on the eye. Hold that half press to hold focus, reposition the camera for framing and complete your shot. Also, use a little pop of fill flash, even in daylight for outdoor people shots, to fill in shadows and put a bit of catchlight in the eyes. If you wanted the background to be dark like it is, then set your exposure accordingly, then the fill flash would have brightened his face. You can adjust the flash output. A separate flash unit in the hot shoe is preferred, especially with a large lens like the one you are using. However, if in daylight bright enough, you might get away just fine using the built-in flash. Red eye would not be a problem, and any shadow in the lower part of the frame cast by the large lens may not be noticeable- just remove the lens hood.

You really do not need 1/400 sec for fine results in shooting photos of a person just standing there. The upper normal flash sync with the K-70 is probably 1/180 sec which is plenty. In fact, you might be able to reduce your ISO, depending on how bright the day is. Take readings of the background without your subject first to get an idea of optimum exposure without the flash operational, and then be sure shutter speed does not exceed 1/180 sec. You can go as low as 1/125 sec or even a bit lower for a still person. You can keep your aperture to f/3.5 if that blurs your background well, as it has in your sample photo, manipulating exposure also by using the ISO setting.


---------- Post added 04-09-20 at 07:12 PM ----------

I think there was definitely a problem with the lens.
While pics aren't generally as sharp as I'd like, the pics from this lens were awful.

QuoteOriginally posted by CarlJF Quote
It's difficult to say just with only this picture. As others said, it could be a back or front focus issue, but it also could be a misfocus. Unfortunately the data about how the picture was focused are missing in the exif. So, it's hard to tell... You could make a few test pictures using Liveview. If the softness disappear it would strongly suggest a focus issue. On a portrait like this, at 70mm f3.5, there's about 6 inches of DOF and even a slight misfocus could make the picture appears softer than it should be...


As said above, the lens is at its worst: longest end and almost fully open. So, some softness might just be normal with this lens under these conditions... What about other focal length ? Are the pictures still soft at 50mm f5.6 ?


---------- Post added 04-09-20 at 07:12 PM ----------

I think there was definitely a problem with the lens.
While pics aren't generally as sharp as I'd like, the pics from this lens were awful.

QuoteOriginally posted by CarlJF Quote
It's difficult to say just with only this picture. As others said, it could be a back or front focus issue, but it also could be a misfocus. Unfortunately the data about how the picture was focused are missing in the exif. So, it's hard to tell... You could make a few test pictures using Liveview. If the softness disappear it would strongly suggest a focus issue. On a portrait like this, at 70mm f3.5, there's about 6 inches of DOF and even a slight misfocus could make the picture appears softer than it should be...


As said above, the lens is at its worst: longest end and almost fully open. So, some softness might just be normal with this lens under these conditions... What about other focal length ? Are the pictures still soft at 50mm f5.6 ?
04-12-2020, 12:04 AM - 1 Like   #8
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Well, there could be a slight mis-focus going on in need of AF fine tuning adjustment. But all the other matters I brought up are still at play in this photo. The lens has a very good reputation. I do not own one myself. If you are shooting JPEG images, be sure to set "Fine Sharpening" in the Custom Image menus, especially in the most-often used "Bright" category, but doing so in the "Natural" category is a good idea too, for the best fine detail in your results.

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