Can't get my lens to 3.8 even though it is a 3.8 -22 lens

Hazcat · 05-08-2016, 07:35 AM

Hi guys. I bought a used Pentax 28-200 f3.8 lens. I mounted it on my K-S2 and generally like the lens BUT ....

I cannot get it to go below 5.6. Did I limit it somewhere in the menu system or is there a way to force the camera to recognize the 3.8?

Thanks

**boriscleto** · 05-08-2016, 07:54 AM

Originally posted by Hazcat

Hi guys. I bought a used Pentax 28-200 f3.8 lens. I mounted it on my K-S2 and generally like the lens BUT ....

I cannot get it to go below 5.6. Did I limit it somewhere in the menu system or is there a way to force the camera to recognize the 3.8?

Thanks

At what focal length? The 28-200 is a variable aperture lens. It is only F3.8 at the wide end (though a DSLR will see it a F4). At the long end it is F5.6 (71-200mm). From 50mm to 70mm it is F4.5.

Hazcat · 05-08-2016, 08:14 AM

Originally posted by boriscleto

At what focal length? The 28-200 is a variable aperture lens. It is only F3.8 at the wide end (though a DSLR will see it a F4). At the long end it is F5.6 (71-200mm). From 50mm to 70mm it is F4.5.

DUH! on me but even at the 28 end it will only go to 4.0.

victormeldrew · 05-08-2016, 08:32 AM

You're using it on a DSLR, yes?

Originally posted by boriscleto

a DSLR will see it a F4

As in, it will read as f4.0 even though it is fractionally wider.

Hazcat · 05-08-2016, 05:38 PM

Originally posted by victormeldrew

You're using it on a DSLR, yes?

As in, it will read as f4.0 even though it is fractionally wider.

Yes K-S2. Will it not read any f stop below 4?

MPrince · 05-08-2016, 05:47 PM

Originally posted by Hazcat

Yes K-S2. Will it not read any f stop below 4?

Yes, it will, but 3.8 is neither a full stop, half stop, or third stop, so your camera display rounds to the nearest, which is 4.

Hazcat · 05-08-2016, 06:26 PM

Originally posted by MPrince

Yes, it will, but 3.8 is neither a full stop, half stop, or third stop, so your camera display rounds to the nearest, which is 4.

So if I had a 1.8 it would read as 2? The Camera wouldn't take the .2 in account?

victormeldrew · 05-08-2016, 06:37 PM

f1.8 is on a third stop increment so your camera would indeed read it. The full details are available on wikipedia, but it involves a lot of boring maths. In the end your display is just rounding to the nearest available amount and that lens falls in between.

Hazcat · 05-08-2016, 06:52 PM

OK thanks!!

Not a Number · 05-08-2016, 07:11 PM

What are your EV steps set to in the custom menu? 1/2 or 1/3? Try setting it to 1/3rd steps.

Hazcat · 05-08-2016, 07:39 PM

Originally posted by Not a Number

What are your EV steps set to in the custom menu? 1/2 or 1/3? Try setting it to 1/3rd steps.

It is set to 1/3. Thanks.

emalvick · 05-10-2016, 03:20 PM

I think it'll be fine. I'm not sure I've had a 3.8 lens. It would be curious as to whether when it is wide open, does one adjustment keep it at 4.0 since it is in theory wider than 4.0.

Otherwise, how do you know that you are not at f4 or that the camera is actually opening up fully? This seems like it could be problematic if you are shooting in manual mode.

builttospill · 05-10-2016, 07:36 PM

I haven't had a lens with an aperture of f/3.8, but my K10D shows f/1.9 with my FA 43. It doesn't round when the aperture is all the way open.

Hazcat · 05-11-2016, 05:22 AM

Originally posted by builttospill

I haven't had a lens with an aperture of f/3.8, but my K10D shows f/1.9 with my FA 43. It doesn't round when the aperture is all the way open.

Not sure what you mean by one adjustment. I am curious if it will be overexposed.

builttospill · 05-11-2016, 08:40 PM

Originally posted by Hazcat

Not sure what you mean by one adjustment. I am curious if it will be overexposed.

Sorry, I'm not sure what you mean either. But what I was trying to say is f/3.8 is odd and so is f/1.9. I have a lens with an aperture of f/1.9 when it's wide open. My camera does not round it to f/2, but instead shows f/1.9 and f/2 as two separate aperture settings. I've never heard of a camera rounding the aperture setting display, so that would surprise me if that is what's happening.

Instead I'm wondering if the camera is registering that the lens is all the way zoomed out.

05-08-2016, 07:35 AM	#1
Hazcat Junior Member Join Date: Dec 2015 Posts: 28	Can't get my lens to 3.8 even though it is a 3.8 -22 lens Hi guys. I bought a used Pentax 28-200 f3.8 lens. I mounted it on my K-S2 and generally like the lens BUT .... I cannot get it to go below 5.6. Did I limit it somewhere in the menu system or is there a way to force the camera to recognize the 3.8? Thanks

05-08-2016, 05:47 PM	#6
MPrince Veteran Member Join Date: Sep 2006 Location: WV Posts: 1,495	Originally posted by Hazcat Yes K-S2. Will it not read any f stop below 4? Yes, it will, but 3.8 is neither a full stop, half stop, or third stop, so your camera display rounds to the nearest, which is 4. Last edited by MPrince; 05-08-2016 at 05:52 PM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Sigma 18-300 lens can't get auto focus to work	Ken Kroska	Visitors' Center	6	03-27-2016 07:49 PM
Is it possible for K-3 to get pixel shift ability?	Zebrafish	Pentax K-3 & K-3 II	12	10-28-2015 10:42 AM
Sigma can't repair my 50 F2.8 macro as it is discontinued - who can?	JinDesu	Pentax SLR Lens Discussion	12	08-24-2013 12:23 PM
Is it possible to use a MICRO 4/3 lens on a FF DSLR?	iNicole	Pentax SLR Lens Discussion	15	10-11-2012 07:36 PM
can't get apertue to f 3.5	lilcoco	Troubleshooting and Beginner Help	3	08-23-2010 09:09 AM

05-08-2016, 07:54 AM	#2
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Originally posted by Hazcat Hi guys. I bought a used Pentax 28-200 f3.8 lens. I mounted it on my K-S2 and generally like the lens BUT .... I cannot get it to go below 5.6. Did I limit it somewhere in the menu system or is there a way to force the camera to recognize the 3.8? Thanks At what focal length? The 28-200 is a variable aperture lens. It is only F3.8 at the wide end (though a DSLR will see it a F4). At the long end it is F5.6 (71-200mm). From 50mm to 70mm it is F4.5.

05-08-2016, 08:14 AM	#3
Hazcat Junior Member Join Date: Dec 2015 Posts: 28 Original Poster	Originally posted by boriscleto At what focal length? The 28-200 is a variable aperture lens. It is only F3.8 at the wide end (though a DSLR will see it a F4). At the long end it is F5.6 (71-200mm). From 50mm to 70mm it is F4.5. DUH! on me but even at the 28 end it will only go to 4.0.

05-08-2016, 08:32 AM	#4
victormeldrew Veteran Member Join Date: Jun 2015 Location: South West UK Photos: Albums Posts: 1,493	You're using it on a DSLR, yes? Originally posted by boriscleto a DSLR will see it a F4 As in, it will read as f4.0 even though it is fractionally wider.

05-08-2016, 05:38 PM	#5
Hazcat Junior Member Join Date: Dec 2015 Posts: 28 Original Poster	Originally posted by victormeldrew You're using it on a DSLR, yes? As in, it will read as f4.0 even though it is fractionally wider. Yes K-S2. Will it not read any f stop below 4?

05-08-2016, 06:26 PM	#7
Hazcat Junior Member Join Date: Dec 2015 Posts: 28 Original Poster	Originally posted by MPrince Yes, it will, but 3.8 is neither a full stop, half stop, or third stop, so your camera display rounds to the nearest, which is 4. So if I had a 1.8 it would read as 2? The Camera wouldn't take the .2 in account?

05-08-2016, 06:37 PM	#8
victormeldrew Veteran Member Join Date: Jun 2015 Location: South West UK Photos: Albums Posts: 1,493	f1.8 is on a third stop increment so your camera would indeed read it. The full details are available on wikipedia, but it involves a lot of boring maths. In the end your display is just rounding to the nearest available amount and that lens falls in between.

05-08-2016, 06:52 PM	#9
Hazcat Junior Member Join Date: Dec 2015 Posts: 28 Original Poster	OK thanks!!

05-08-2016, 07:11 PM	#10
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	What are your EV steps set to in the custom menu? 1/2 or 1/3? Try setting it to 1/3rd steps.

05-08-2016, 07:39 PM	#11
Hazcat Junior Member Join Date: Dec 2015 Posts: 28 Original Poster	Originally posted by Not a Number What are your EV steps set to in the custom menu? 1/2 or 1/3? Try setting it to 1/3rd steps. It is set to 1/3. Thanks.

05-10-2016, 03:20 PM	#12
emalvick Veteran Member Join Date: Feb 2008 Location: Davis, CA Photos: Gallery Posts: 1,642	I think it'll be fine. I'm not sure I've had a 3.8 lens. It would be curious as to whether when it is wide open, does one adjustment keep it at 4.0 since it is in theory wider than 4.0. Otherwise, how do you know that you are not at f4 or that the camera is actually opening up fully? This seems like it could be problematic if you are shooting in manual mode.

05-10-2016, 07:36 PM	#13
builttospill Pentaxian Join Date: Jun 2009 Location: Utah, Idaho Photos: Gallery Posts: 2,398	I haven't had a lens with an aperture of f/3.8, but my K10D shows f/1.9 with my FA 43. It doesn't round when the aperture is all the way open.

05-11-2016, 05:22 AM	#14
Hazcat Junior Member Join Date: Dec 2015 Posts: 28 Original Poster	Originally posted by builttospill I haven't had a lens with an aperture of f/3.8, but my K10D shows f/1.9 with my FA 43. It doesn't round when the aperture is all the way open. Not sure what you mean by one adjustment. I am curious if it will be overexposed.

05-11-2016, 08:40 PM	#15
builttospill Pentaxian Join Date: Jun 2009 Location: Utah, Idaho Photos: Gallery Posts: 2,398	Originally posted by Hazcat Not sure what you mean by one adjustment. I am curious if it will be overexposed. Sorry, I'm not sure what you mean either. But what I was trying to say is f/3.8 is odd and so is f/1.9. I have a lens with an aperture of f/1.9 when it's wide open. My camera does not round it to f/2, but instead shows f/1.9 and f/2 as two separate aperture settings. I've never heard of a camera rounding the aperture setting display, so that would surprise me if that is what's happening. Instead I'm wondering if the camera is registering that the lens is all the way zoomed out.