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04-03-2016, 02:17 PM   #1
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Legacy Lenses producing REALLY grainy results with K-x.

Hi, I use a Pentax K-x and up until recently only used the kit lens. I discovered the other day that lots of my analogue cameras had lenses with K mounts so I could use them on my DSLR.

The lenses I have been using now are Sigma 70-210mm f/4-5.6 and Miranda 28-70mm f/3.5-4.8. The former is an 'A' lens so I can shoot it in any setting easily, and the latter I use stop down metering to shoot.

Anyway, both seem to be producing REALLY grainy results that aren't particularly sharp in focus no matter the settings of ISO etc. My kit lens seems a lot less grainy in comparison at the exact same settings. I have added images below to show examples.

Below Image shows Kit Lens result and zoomed in - little grain.


Below shows 70-210 result and zoomed in - lots of grain.


Below shows 28-70 result and zoomed in - lots of grain.


I'm not sure if I'm doing anything wrong but any advise or wisdom will be appreciated!
Thanks in advance!

04-03-2016, 02:33 PM   #2
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The last example is out of focus; the other two I'd consider to be quite good actually.

Grain comes from the sensor, not the lens. Turn down the ISO and you should see even better results, as long as there is sufficient ambient light

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04-03-2016, 02:49 PM   #3
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QuoteOriginally posted by eescvc Quote
... no matter the settings of ISO etc.
Are you sure? Lenses don't produce any grain, that'd be the film or sensor. It is important to note that a lot of legacy lenses aren't especially sharp. Some primes (like the M/A 50 f/1.7 etc.) can produce great results, but especially legacy zooms show weaknesses on modern, high resolution sensors and deliver worse images than many modern kit lenses.
04-03-2016, 02:54 PM   #4
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Thanks Adam, yeah I noticed the last one is actually in focus on the jumper! Haha. I find it hard to focus that lens in particular! I've played with lowering my ISO and they still seem really grainy to me. All of my 'digital' lenses (kit, a few macro rings, and a fisheye aswell) have no grain when using the exact same settings. Could there be anything else affecting it?

04-03-2016, 02:56 PM   #5
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Also you always get more "apparent grain" in shadow detail, but this can usually be addressed in PP.
04-03-2016, 02:58 PM   #6
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Lowest ISO number means least noise/grain. Does the K-x have extended or boost ISO? You should enable that feature so you can access the lowest values. If you have highlight correction or shadow correction enabled, this can also emphasize some noise (as it artificially brightens/darkens the photo.

Can lenses make noise? Kind of doubt it. It might be some indirect effect. For example, some lenses have a lower f-number. This means less light, so you have to compensate for it by increasing ISO - thus adding noise.
04-03-2016, 03:03 PM   #7
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I think I need to play with the lenses more tomorrow then! I knew ISO would be the problem but I took the macro above at ISO 400 so I'm not sure why it would be as grainy as it is.
04-03-2016, 03:27 PM   #8
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Post full EXIF info. My guess is that you are using different settings, and the legacy lenses are getting higher ISO settings leading to grainy looking shots.

04-03-2016, 05:06 PM   #9
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As others have noted the lens does not produce the grain the sensor does. Grain or noise in digital is affected by the ISO settings mostly, but also shows up more in underexposed images. Legacy lenses may cause the camera to expose differently than you might expect with modern lenses. If this is the case for a particular lens it can be corrected for by using the exposure compensation adjustment.

Watch the ISO numbers and post examples with the EXIF intact.
04-03-2016, 07:22 PM - 1 Like   #10
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QuoteOriginally posted by eescvc Quote
Hi, I use a Pentax K-x and up until recently only used the kit lens. I discovered the other day that lots of my analogue cameras had lenses with K mounts so I could use them on my DSLR.

The lenses I have been using now are Sigma 70-210mm f/4-5.6 and Miranda 28-70mm f/3.5-4.8. The former is an 'A' lens so I can shoot it in any setting easily, and the latter I use stop down metering to shoot.

Anyway, both seem to be producing REALLY grainy results that aren't particularly sharp in focus no matter the settings of ISO etc. My kit lens seems a lot less grainy in comparison at the exact same settings. I have added images below to show examples.

Below Image shows Kit Lens result and zoomed in - little grain.


Below shows 70-210 result and zoomed in - lots of grain.


Below shows 28-70 result and zoomed in - lots of grain.


I'm not sure if I'm doing anything wrong but any advise or wisdom will be appreciated!
Thanks in advance!
Neither of your legacy lenses are good lenses. They were considered to be junk when they were made, and its doubtful that they have gotten any better over the years. This isn't causing your noise issues, but it is causing your poor imaging issues.
04-04-2016, 12:41 AM - 1 Like   #11
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Also, even at the same f-stop, there could be a t-stop difference, hence the differences in exposure/SNR/noise.
04-04-2016, 04:23 AM   #12
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QuoteOriginally posted by LensBeginner Quote
Also, even at the same f-stop, there could be a t-stop difference, hence the differences in exposure/SNR/noise.
Yeah, this could be a big one. And if the jpeg mode adds contrast to the image or lifts the shadows a little, then even ISO 400 on a K-x can show noise. If you shoot raw and maybe add fill light or exposure, then this will also cause a lot of noise. And if you use black and white presets, then make sure that they don't include "grain" - some black and white actions actually add "film style" grain to the photos

Anyway, you can remedy the situation by using lower ISO and longer shutter speed, and keeping the aperture below f9. You can get a camera like K-5 (or K-5II, K-5IIs, even K-50, K-30; the 16MP sensor is better than the 12MP of the K-x and K-r), which will give you better dynamic range and lower noise at the same ISO. Or lenses that are faster and more contrasty. Your photos are pretty good already, so if you get better glass, it will be top notch stuff. Once you get enough skills, you will really appreciate higher tier gear.
I can tell you that my K-r (same sensor as K-x) allows less PP than the K-01 (which has same sensor as K-5, but lower bit depth. This sensor renders colours nicely and has really great noise performance)
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