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01-12-2015, 12:05 AM   #1
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K50 - depth of field preview

Hey

I just have bought K-50 +DA 18-135. However I realized that depth of field (DOF) preview (via viewfinder and activated by button on the left) works only when focal length of DA is 18 to 35 mm. Above 35 mm it doesn't work. Is it a malfunction or intended operation?

Greets

01-12-2015, 12:13 AM - 1 Like   #2
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What aperture were you using? If you're close to wide-open DOF preview will either differ very little or not at all compared to what you normally see.

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01-12-2015, 12:29 AM   #3
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QuoteOriginally posted by Adam Quote
What aperture were you using? If you're close to wide-open DOF preview will either differ very little or not at all compared to what you normally see.

True just checked it. When focal length of DA is 100 mm and aperture is set to F18 everything is working fine.
I was just confused because at 100 mm and aperture set to F5,6 the DOF was some kind of blocked; shooting information in viewfinder was still displayed when DOF preview button was pressed.
01-12-2015, 12:50 AM - 1 Like   #4
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QuoteOriginally posted by ps1984 Quote
True just checked it. When focal length of DA is 100 mm and aperture is set to F18 everything is working fine.
I was just confused because at 100 mm and aperture set to F5,6 the DOF was some kind of blocked; shooting information in viewfinder was still displayed when DOF preview button was pressed.
Great! F5 is indeed the max aperture at 100mm.


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01-12-2015, 12:16 PM   #5
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QuoteOriginally posted by Adam Quote
Great! F5 is indeed the max aperture at 100mm.
Yes F5,6 is max aperture for 100 mm

Thanks!

Another question maybe not strictly related to topic but:

why DA 18-135 WR lens doesn't have DOF scale like in link below?

Using DOF Scales
01-12-2015, 01:07 PM   #6
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QuoteOriginally posted by ps1984 Quote
why DA 18-135 WR lens doesn't have DOF scale like in link below?
This has become a trend on consumer lenses.

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01-14-2015, 12:37 AM   #7
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QuoteOriginally posted by ps1984 Quote
why DA 18-135 WR lens doesn't have DOF scale like in link below?
Adam gave one reason.

The other one is that DOF depends on (amongst other parameters) focal length. This means that 'one' DOF scale does not fit all, you need a sliding scale as demonstrated for e.g. a Minolta MD70-210 in the last picture on ru_fotoplenka: Minolta MD Zoom 70-210\4

This lens is a push-pull zoom; it only has one ring that you can push and pull for zooming and turn for focusing. In the shown zoom position (70mm) you can see a quite deep DOF; pulling the ring towards the mount moves the zoom position (eventually) to 210mm where we have a very shallow DOF, even at f/32). You will also notice that there are only a few lines for different apertures (f/32, f/16 and f/8), else it became too busy.

I guess your 18-135 is a two-ring zoom and it's not possible to have a sliding scale on that.
01-27-2015, 12:51 PM   #8
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Hey

thanks for explanation.

DA 18-55 mm has DOF scale but focal length span is lesser than in DA 18-135 so maybe that is the reason.

I also saw something from Nikkor 35-105 mm (attachment picture) - I guess its kind of combined DOF scale; that ring type for 35 mm and the rest for other.

QuoteOriginally posted by sterretje Quote
Adam gave one reason.

The other one is that DOF depends on (amongst other parameters) focal length. This means that 'one' DOF scale does not fit all, you need a sliding scale as demonstrated for e.g. a Minolta MD70-210 in the last picture on ru_fotoplenka: Minolta MD Zoom 70-210\4

This lens is a push-pull zoom; it only has one ring that you can push and pull for zooming and turn for focusing. In the shown zoom position (70mm) you can see a quite deep DOF; pulling the ring towards the mount moves the zoom position (eventually) to 210mm where we have a very shallow DOF, even at f/32). You will also notice that there are only a few lines for different apertures (f/32, f/16 and f/8), else it became too busy.

I guess your 18-135 is a two-ring zoom and it's not possible to have a sliding scale on that.


Attached Images
 
01-28-2015, 03:49 AM   #9
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QuoteOriginally posted by ps1984 Quote
DA 18-55 mm has DOF scale but focal length span is lesser than in DA 18-135 so maybe that is the reason.
The 18-55 does not have a DOF scale. I have the DA18-55AL/WR and the DA18-55AL/II in front of me. They have a distance scale and a focal length scale, but no DOF scale; the DAL version does not have the distance scale as far as I know, but I might be mistaken.

Look at the curved lines in the image that I linked, those are the lines that indicate the DOF. The lens is set to 1.1m distance and 70mm focal length; if an aperture of f/8 is chosen, you follow the curved lines indicated by 8 (the closest to the straight line on the housing) and you will see that the DOF is from (approx) 1.05m to 1.15m. If you pull the zoom ring towards the mount (focal length 100 cm) you can see that the curved lines are closer to the straight line and your DOF is approx. 2.5 centimeters behind and in front of the focus distance.

I don't know about the Nikon; but no DOF scale (curved lines).
04-13-2015, 11:30 AM   #10
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So what is the difference between DOF scale, distance scale and focal length scale?

Here, in link below, I see definition of DOF scale:

Using DOF Scales

And yes I see that DA 18-55 has something like distance scale, so what is purpose for distance scale then?

Greets

QuoteOriginally posted by sterretje Quote
The 18-55 does not have a DOF scale. I have the DA18-55AL/WR and the DA18-55AL/II in front of me. They have a distance scale and a focal length scale, but no DOF scale; the DAL version does not have the distance scale as far as I know, but I might be mistaken.

Look at the curved lines in the image that I linked, those are the lines that indicate the DOF. The lens is set to 1.1m distance and 70mm focal length; if an aperture of f/8 is chosen, you follow the curved lines indicated by 8 (the closest to the straight line on the housing) and you will see that the DOF is from (approx) 1.05m to 1.15m. If you pull the zoom ring towards the mount (focal length 100 cm) you can see that the curved lines are closer to the straight line and your DOF is approx. 2.5 centimeters behind and in front of the focus distance.

I don't know about the Nikon; but no DOF scale (curved lines).
04-13-2015, 09:20 PM   #11
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QuoteOriginally posted by ps1984 Quote
what is purpose for distance scale then?
For manual focus without the viewfinder


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04-13-2015, 10:29 PM   #12
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Focal length scale indicates which focal length you have choosen; 18mm for a wide view, 135mm for a maximum zoomed in view etc.
Distance scale indicates at which point you or the camera has found point to focus on.

DOF scale (in the picture in the article you linked to) shows a number of apertures. The lens is focused at 9 meters (30 feet). If you choose an aperture of e.g. f/4, your DOF will be from roughly 7 to 10 meters. If you choose f/22, the DOF will be from roughly 4.5 meters to infinity.

Note that there is a difference in DOF for a lens mounted on full frame/film or on APSc. For APSc, you need to roughly use one stop slower than indicated, so if the scale states f/4 for the required DOF, you need to set it to f/5.6. This certainly applies to lenses from the film era on APSc; I'm not sure if there are dedicated APSc lenses with a DOF scale and if there are, if the DOF scale is for APSc or FF.

There are DOF calculators on the web (e.g. Online Depth of Field Calculator ) and for smart phones.
04-14-2015, 11:38 AM   #13
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QuoteOriginally posted by sterretje Quote
I'm not sure if there are dedicated APSc lenses with a DOF scale and if there are, if the DOF scale is for APSc or FF.
There are many. A quick glance down the DA prime page on this site shows that with a few exceptions, almost all Pentax-DA series primes have DOF scales.

Pentax DA Prime Lenses - Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database

DOF scales are pretty much absent from modern APS-C zooms.


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04-14-2015, 09:51 PM   #14
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QuoteOriginally posted by stevebrot Quote
There are many. A quick glance down the DA prime page on this site shows that with a few exceptions, almost all Pentax-DA series primes have DOF scales.
You're right; I knew it but forgot about it. Just a bit difficult to judge if they're 'calibrated' for APSc or for FF.
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