TAv Mode and DA* 16-50mm

imagesforyou · 09-21-2011, 05:09 AM

I've discovered that when using my K5 -w- my new DA* 16-50mm lens in TAv mode, the ISO setting will vary when zooming, even though the lens is a constant f2.8. Isn't the whole purpose of a constant aperture lens to avoid this? It seems the ISO should stay constant in this condition, or am I missing something?

Thanks,
Steve

areidjr · 09-21-2011, 05:39 AM

I would think that, unless you are pointing it at a white wall, the scene will be changing as you zoom and the metering will need to change the ISO to adjust the exposure. I suppose that if you were using spot metering that the ISO would be more likely to remain constant as you zoom.

gtl · 09-21-2011, 05:41 AM

I think the metering is affecting the ISO. When you zoom in and out the camera meters differently as the scene changes. Try spot metering and zooming in and out. It should not change then.

Edit: oops I was beaten to it

Rupert · 09-21-2011, 06:35 AM

Zooming and panning are similar in changing the metering.......Tav is my most used mode, I don't worry much about the ISO, but then again, I am not as particular on the results as some. If I get a Squirrel, I'm happy!

Regards!

09-21-2011, 05:09 AM	#1
imagesforyou Forum Member Join Date: Sep 2009 Location: Waukesha, Wisconsin Posts: 58	*TAv Mode and DA 16-50mm** I've discovered that when using my K5 -w- my new DA* 16-50mm lens in TAv mode, the ISO setting will vary when zooming, even though the lens is a constant f2.8. Isn't the whole purpose of a constant aperture lens to avoid this? It seems the ISO should stay constant in this condition, or am I missing something? Thanks, Steve

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Used the TAv mode today - cool!	PALADIN85020	Pentax K-5 & K-5 II	61	06-28-2012 07:46 AM
TAv Mode	L33tGreg	Pentax DSLR Discussion	4	07-21-2011 01:20 PM
K-5 has renewed my love of TAv mode. You?	m8o	Pentax K-5 & K-5 II	15	11-28-2010 12:39 PM
Using the TAv mode with the K7 ... question.	jpzk	Troubleshooting and Beginner Help	10	11-22-2010 07:10 PM
TAv mode	Howard2k	Pentax DSLR Discussion	17	09-23-2010 01:30 PM

09-21-2011, 05:39 AM	#2
areidjr Veteran Member Join Date: Sep 2007 Location: Pittsburgh, Pa, USA Photos: Gallery Posts: 529	I would think that, unless you are pointing it at a white wall, the scene will be changing as you zoom and the metering will need to change the ISO to adjust the exposure. I suppose that if you were using spot metering that the ISO would be more likely to remain constant as you zoom.

09-21-2011, 05:41 AM	#3
gtl Veteran Member Join Date: Feb 2010 Posts: 349	I think the metering is affecting the ISO. When you zoom in and out the camera meters differently as the scene changes. Try spot metering and zooming in and out. It should not change then. Edit: oops I was beaten to it

09-21-2011, 06:35 AM	#4
Rupert Veteran Member Join Date: Sep 2006 Location: Texas Photos: Gallery \| Albums Posts: 25,123	Zooming and panning are similar in changing the metering.......Tav is my most used mode, I don't worry much about the ISO, but then again, I am not as particular on the results as some. If I get a Squirrel, I'm happy! Regards!