Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-24-2011, 10:20 PM   #1
New Member




Join Date: Jan 2011
Posts: 4
Please help with Pentax Kx and Pentax-M 50mm manual lens

Getting low shutter speeds and unable to control flash - when using Pentax-M 50mm 1.7 with K-x

I recently purchased a Pentax-M 50mm 1.7 lens - to use with my Pentax k-x.

Settings on the camera -
** custom setting - Using aperture ring - Permitted.
** focal length on startup 50mm.
** Green button - action in M mode - Tv Shift.
** SR - on

For indoor shots in M mode with aperture ring dial at 1.7 (wide open) - at moderate lighting (tube lights) - pressing green button gives me a shutter speed of 1/5 to 1/15 max - which is significantly lower to be able to snap non-blur pictures of my toddler !

The ISO is typically set at 400.

Another issue - in-built Flash (at any compensation level) white washes my pictures.
I am at my wits end - I thought these are faster lens - and would be a decent upgrade to my kit lens. I can use tripods - but that can only do so much.

The apertures seem to open and shut properly with its widest at 1.7. Now - is there anthing else I should be doing ? Did I get some faulty lens ? Or is this normal and just not enough for the challenge I am putting those to ? I do not like flashes - but even that seems to not work with this lens ! My kit lens right now appears to be more useful and faster - even with its smaller apertures

01-24-2011, 11:20 PM   #2
Inactive Account




Join Date: Aug 2008
Location: Michigan, USA
Photos: Gallery | Albums
Posts: 7,484
Your camera and lens are working properly. You cannot 'control' the flash with an M type lens. It will always fire at full power. You'll have to dial your ISO down and stop the lens down.

01-24-2011, 11:24 PM   #3
Senior Member
sajah's Avatar

Join Date: Mar 2009
Location: South Korea
Photos: Gallery
Posts: 275
Try using higher ISO, something like ISO 1600 or even 3200. K-x has very good high ISO so don't be afraid to do so.

Also, you can use Av mode as long as you plan to keep the aperture wide open.

Regarding the flash, it can't work because it can't figure out the current aperture. In another word, it's always like that with any M lenses so there's nothing wrong with yours. You need A lens (or of course F, FA or DA) for the internal flash to work.

The internal flash will always fire full power with your lens. While you can't control it, there should be a appropriate setting (aperture, shutter and distance) where the picture comes out perfectly. However this most likely involves small aperture say F8, and I don't think that's what you want (most of the time) with a fast fifty like this.

Hope it helps!
01-24-2011, 11:47 PM - 1 Like   #4
Veteran Member
KxBlaze's Avatar

Join Date: Feb 2010
Location: California
Photos: Gallery
Posts: 1,594
The green button will not always give you the most accurate shutter speed for the given aperture (it always tells me 1/5 or so even when at 1.7, outside during the middle of the day) so I suggest trial and error. At 1.7, ISO 400 and moderate lighting you should be much faster than 1/5 so do not always trust the green button. If things are whited out just speed up the shutter, lower the ISO or close the aperture, trial and error.

01-25-2011, 03:57 PM   #5
Pentaxian
paulh's Avatar

Join Date: Sep 2010
Location: DFW Texas
Photos: Gallery | Albums
Posts: 13,866
QuoteOriginally posted by KxBlaze Quote
The green button will not always give you the most accurate shutter speed for the given aperture (it always tells me 1/5 or so even when at 1.7, outside during the middle of the day) so I suggest trial and error. At 1.7, ISO 400 and moderate lighting you should be much faster than 1/5 so do not always trust the green button. If things are whited out just speed up the shutter, lower the ISO or close the aperture, trial and error.
+1 on this ^. For my manual lens indoor shots with the pop-up flash, I always crank up the shutter speed from what the green button recommends. Experiment with different distances & shutter speeds, & you will eventually dial in some settings that'll work for you.

Paul
01-25-2011, 04:38 PM   #6
Ira
Inactive Account




Join Date: Mar 2009
Location: Coral Springs, FL
Photos: Gallery | Albums
Posts: 5,216
The green button doesn't do anything when you're working with flash with a manual lens.

1) You simply set your shutter speed to 180, the fastest flash sync speed. (If the pop-up is already up, it won't go any faster). So now, if you hit the green button with a manual lens, it doesn't know the flash is even there, and it's going to meter as if the flash didn't exist at all.--and this is whether the flash is up or not. (That's why your shots are overexposed and washed out.)

2) FYI: On the K-x, in M mode, and you're shooting without flash, you don't have to use the Green button for this. The ev+- button does the same thing.

3) So for pop-up flash use, set your ISO to 400 (manual ISO!), set shutter speed to 180, set aperture to F8, DON'T touch the Green button OR the ev button, and pull the trigger. If what you're trying to shoot is underexposed, open your aperture to 5.6. If it's washed out and overexposed, stop down to F11, or change ISO to 200.

The camera doesn't do any metering at all, and it SHOULDN'T. with manual lenses in conjunction with a flash. You actually have to pretend that you don't HAVE a meter when it comes to manual lenses and flash.

Last edited by Ira; 01-25-2011 at 04:48 PM.
01-25-2011, 04:46 PM   #7
Inactive Account




Join Date: Aug 2008
Location: Michigan, USA
Photos: Gallery | Albums
Posts: 7,484
With an M/K type lens on (the same as far as the camera is concerned) regardless of the Mode, it thinks it's in Av mode, except, in M mode. I don't know what you expect to have happen in any other mode with a COMPLETELY manual lens. Your lens is firing Wide Open regardless of what you do in any of the auto modes. No change in speed or ISO is going to change the Over exposure situation in any of the Auto modes.

Secondly, with that type of lens, P-TTL does not work. You will have to go to either Auto (A) mode on the flash or Manual (M) and adjust the output there, with an external flash. With the Camera in M mode, you can set your aperture and ISO on the flash, and set the camera to match it (using the aperture ring) and you should be good to go. The good news about that is once you decide on a setting that works, leave it there and shoot.

01-26-2011, 02:37 PM   #8
New Member




Join Date: Jan 2011
Posts: 4
Original Poster
Thank you all for being so helpful and your valuable advise.

From the posts I gather what I am getting is expected - I must admit that I did not know that I cannot control the flash for manual lens.

The shutter speeds from the green button seems about the right speeds for proper exposure - anything less or more with this lens over/under exposes the picture. Moving from kit lens to the 1.7 50mm did seem to give me a shutter speed advantage - but the shutter speeds of 1/5 to 1/15 is at most times not enough to give non-blur pics of my toddler.

I was expecting the 1.7 to significantly improve the shutter speed situation from what 3.6 gave me - but to my surprise it did only a little - was hoping I was doing something wrong which would explain the situation.

I will try the option to move the ISO higher than 400 - though I suspect it would make my pictures noisy for print - but atleast I will get a picture that way !

I have not played with this lens a lot - but I did not notice a shallow depth of field at 1.7 either.

I will test more at various apertures and see their effect on shutter speeds and depth of field. Will post on my findings.

01-26-2011, 02:51 PM   #9
Ira
Inactive Account




Join Date: Mar 2009
Location: Coral Springs, FL
Photos: Gallery | Albums
Posts: 5,216
For now, forget about shutter speed for using flash for indoor shots. Use the fastest you can, 180.

You see, the flash burst is like 100 times faster than your shutter speed. (I don't know the exact number, but I'm using this as an example.) So what happens is, because the flash fires so short and fast, you want, for now, to be the ONLY light source affecting your exposure. If you used 1/15 shutter speed, you are now allowing ambient light to affect your exposure more than you want it too.

And this will result in BLURRED images, because moving subjects or not, you can't safely handhold at 1/15.

But the main reason to leave it at 180 for now is exposure. You want the flash to be the major light source for the shot, but once you use slower shutter speeds, you're allowing ambient light to play more of an effect. Simply adjust aperture and ISO for proper exposure.

And I only said ISO 400 as a starting point, which won't result in significant noise, and which many people find a good ISO for flash work.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
50mm, aperture, apertures, camera, kit, lens, pentax help, pentax kx, pentax-m, pentax-m 50mm, photography, pictures
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to use a manual 50mm lens on a pentax k-x? Secret Elkina Troubleshooting and Beginner Help 3 12-09-2010 02:35 AM
Trying out manual lens Pentax 50mm f1.7 Mark Morb Post Your Photos! 4 05-31-2009 12:16 AM
For Sale - Sold: Pentax-K 50mm f/1.2 Manual Focus Lens MikeDubU Sold Items 17 02-10-2009 03:22 PM
For Sale - Sold: FS: SMC Pentax-M 1:1.7 50mm Manual Focus Lens carpents Sold Items 2 12-20-2007 08:32 PM



All times are GMT -7. The time now is 04:59 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top