Another nooob question...

nitrox28 · 12-16-2009, 03:32 PM

I've seen the term "step down" used alot, and I'm not so sure I know what it means. I bought a cheap Tamron 28-80mm lens from B&H ($49!) and the only review I could find said that the IQ improves if you step it down. A little insight please?

Novocain · 12-16-2009, 04:01 PM

It refers to stepping down the aperture from the widest available opening to smaller openings.

I do not understand the science behind the IQ improvement. Maybe someone else can shed some light.

deadwolfbones · 12-16-2009, 04:36 PM

Generally the term is "stop down." Most lenses have an optimal aperture with regard to IQ... you can see this in their MTF resolution charts and so on. Stopping down is the act of selecting an aperture narrower than the widest.

For an explanation of "stops," look here.

Marc Sabatella · 12-16-2009, 09:09 PM

And in case you're unfamilair with the basics of exposure, aperture , aka f-stop, is how big the opening inside the lens is. In an fully automatic mode, the camera chooses this for you. If you want to choose your own aperture, use av mode, and the dial then lets you do so. Smaller numbers are larger apertures; stopping down means moving to larger numbers (smaller apertures). Typically best results are obtained about 3-6 clicks of the wheel form the largest aperture (smallest number). In fully automatic mode, it generally does htis for you, as the camera "knows" this too. It would only choose to shoot at the largest aperture if that was the only way to get a high enough shutter speed.

**Canada_Rockies** · 12-16-2009, 09:15 PM

Originally posted by Marc Sabatella

And in case you're unfamilair with the basics of exposure, aperture , aka f-stop, is how big the opening inside the lens is. In an fully automatic mode, the camera chooses this for you. If you want to choose your own aperture, use av mode, and the dial then lets you do so. Smaller numbers are larger apertures; stopping down means moving to larger numbers (smaller apertures). Typically best results are obtained about 3-6 clicks of the wheel form the largest aperture (smallest number). In fully automatic mode, it generally does htis for you, as the camera "knows" this too. It would only choose to shoot at the largest aperture if that was the only way to get a high enough shutter speed.

And Pentax includes MTF program mode which will keep the lens at one or two ideal apertures with any Pentax lens that can tell the camera what the best MTF aperture(s) are. Think FA or later.

12-16-2009, 03:32 PM	#1
nitrox28 Forum Member Join Date: Jul 2009 Location: Kentucky Posts: 62	Another nooob question... I've seen the term "step down" used alot, and I'm not so sure I know what it means. I bought a cheap Tamron 28-80mm lens from B&H ($49!) and the only review I could find said that the IQ improves if you step it down. A little insight please?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Can I ask a question ?	Lloydy	General Talk	1	04-27-2010 05:09 PM
Question	curatolo	Troubleshooting and Beginner Help	4	03-21-2010 04:24 PM
K-m question	adwb	Pentax DSLR Discussion	3	10-30-2009 12:13 PM
K7 question	dafiryde	Pentax DSLR Discussion	29	08-05-2009 12:56 PM
An Answer to a question and a question.	granitic	Pentax DSLR Discussion	5	02-23-2007 09:28 AM

12-16-2009, 04:01 PM	#2
Novocain New Member Join Date: Nov 2009 Location: Pittsburgh PA Photos: Gallery Posts: 21	It refers to stepping down the aperture from the widest available opening to smaller openings. I do not understand the science behind the IQ improvement. Maybe someone else can shed some light.

12-16-2009, 04:36 PM	#3
deadwolfbones Veteran Member Join Date: Sep 2007 Location: La Crescenta, CA Posts: 7,450	Generally the term is "stop down." Most lenses have an optimal aperture with regard to IQ... you can see this in their MTF resolution charts and so on. Stopping down is the act of selecting an aperture narrower than the widest. For an explanation of "stops," look here.

12-16-2009, 09:09 PM	#4
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	And in case you're unfamilair with the basics of exposure, aperture , aka f-stop, is how big the opening inside the lens is. In an fully automatic mode, the camera chooses this for you. If you want to choose your own aperture, use av mode, and the dial then lets you do so. Smaller numbers are larger apertures; stopping down means moving to larger numbers (smaller apertures). Typically best results are obtained about 3-6 clicks of the wheel form the largest aperture (smallest number). In fully automatic mode, it generally does htis for you, as the camera "knows" this too. It would only choose to shoot at the largest aperture if that was the only way to get a high enough shutter speed.

12-16-2009, 09:15 PM	#5
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 12,385	Originally posted by Marc Sabatella And in case you're unfamilair with the basics of exposure, aperture , aka f-stop, is how big the opening inside the lens is. In an fully automatic mode, the camera chooses this for you. If you want to choose your own aperture, use av mode, and the dial then lets you do so. Smaller numbers are larger apertures; stopping down means moving to larger numbers (smaller apertures). Typically best results are obtained about 3-6 clicks of the wheel form the largest aperture (smallest number). In fully automatic mode, it generally does htis for you, as the camera "knows" this too. It would only choose to shoot at the largest aperture if that was the only way to get a high enough shutter speed. And Pentax includes MTF program mode which will keep the lens at one or two ideal apertures with any Pentax lens that can tell the camera what the best MTF aperture(s) are. Think FA or later.