[Na Horuk]

Are you lining up the left "8" mark with infinity? Or whatever aperture you were using? In the example below (with a very dusty da14mm), the lens is set for the hyperfocal distance when shooting at f/8.

I was thinking of uploading a photo, but my membership expired so I cant add attachments Great that you posted it.
And yep, that is how it should look. If you have infinity on the centre point, then only infinity will be in focus (so, stars) and maybe just some of the very-far away objects (clouds, horizon). Note that some modern lenses even allow you to focus past infinity, which is not a great idea. And some third party lenses have miscalibrated infinity. And even things like temperature and air pressure can cause the focus to be miscalibrated. And then there is the whole question of "acceptable" - this often does not mean "super sharp when viewed at 100% on computer screen"

[jatrax]

The one question I have never had answered was how using a crop sensor affected this.
1) On a FF lens such as a Pentax-A can the marks be used as is or do we need to add a stop? I believe Rio Rico felt that the marks as is were for FF and had to be adjusted for APS-C. Others disagreed.

2) On DA lenses such as the 15mm and the 21mm were the marks designed for APS-C and thus should be used as is or do they also need adjusted?

[Na Horuk]

Once someone has K-1 they can do a test - take one shot in FF mode, one shot in APSC mode, without changing the lens, aperture or focus.
I think that a) lens' focal length and aperture are a lens property, and they will render the same image (with the same focus) regardless of format (FF, APSC, MF); however b) sensors have different resolution, different size pixels, which might have various consequences. This is why I think hyperfocal rules from the film days are slightly outdated, and that it makes sense to use a stop different aperture (focus as if you are using a stop wider aperture). But that is just my limited, unscientific, definitely not thorough experience.

2) On DA lenses such as the 15mm and the 21mm were the marks designed for APS-C and thus should be used as is or do they also need adjusted?

This would be a great question to ask Pentax. And not just their marketing department, but the engineers. What exactly was their standard for the markings on the lenses? Then a K-1 test to check the answer empirically

[jatrax]

sensors have different resolution, different size pixels, which might have various consequences. This is why I think hyperfocal rules from the film days are slightly outdated, and that it makes sense to use a stop different aperture (focus as if you are using a stop wider aperture).

Good point, and maybe that was Rio Rico's point as well. I'll have to go back and see if I can find that thread. I know that I struggled with hyperfocal using Pentax-A lenses. Using the marks as laid out on the lens did not produce the results I expected and I asked a question similar to the OP's.

[BrianR]

The one question I have never had answered was how using a crop sensor affected this.
1) On a FF lens such as a Pentax-A can the marks be used as is or do we need to add a stop? I believe Rio Rico felt that the marks as is were for FF and had to be adjusted for APS-C. Others disagreed.

To get the same level of "acceptably in focus" under the same viewing conditions (print size and viewing distance), then you'd need to close the aperture down one stop on aps-c if you're using the hyperfocal guide on a 35mm film lens. For example, set the focusing ring to the f/8 mark of your film lens, you should stop down to f/11 when on a k-3. But see below.

2) On DA lenses such as the 15mm and the 21mm were the marks designed for APS-C and thus should be used as is or do they also need adjusted?

Good question, best bet would be to take a da lens with the markings and compare with a pentax film lens of the same focal length. Wider the focal length the better as the marks get really close and difficult to tell anything with any accuracy as FL goes up. I only have the DFA100mm and an m42 100mm to compare, the dof scales are tiny, and the dfa100mm might not say anything about a general da lens.

The concept of "acceptably in focus" cannot be stressed enough, and this changes depending on your standards or viewing conditions or eyesight, etc. and your version may not match whoever did the calculations for the old film lenses or the da lenses. I think it's best to use the markings as a guide so you can be somewhat consistent when you finding settings that work for you.

[jatrax]

I'll have to go back and see if I can find that thread.

Here is the old thread: https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/183231-how-...cale-lens.html See post #4

---------- Post added 03-05-16 at 09:34 AM ----------

best bet would be to take a da lens with the markings and compare with a pentax film lens of the same focal length

Great idea! Now why didn't I think of that? Duh...

Ok, I happen to have on my desk a Pentax-A 20mm f/2.8 and a Pentax DA 21mm Limited. Perfect for this I would think!

Using the extreme of f/22:
Pentax-A 20mm shows in focus from infinity to 1.1ft
Pentax DA 21mm shows in focus from infinity to 1.8ft

Pentax-A 20mm f/2.8:
f/22 = ∞ to 1.1ft
F/16 = ∞ to 1.35ft
f/8 = ∞ to 3ft

Pentax DA 21mm:
f/22 = ∞ to 1.8ft
F/16 = ∞ to 2.2ft
f/8 = ∞ to ?????

Distances approximated as honestly those little marks are kinda hard to interpret. And there is nothing on the DA 21mm to even guess at f/8

[house]

On my da21 ltd I've made my own markings. The etched in ones weren't accurate enough and I only need f8 and f11 markings. So I put my camera with aperture f8 on a tripod measured out the theoretical hyperfocal distance (can be calculated on various websites) from the crossed 0 on the body to a high contrast target. Used the autofocus (live view) to focus on the target. I then put a thin (4mm) strip of masking tape across the barrel/focus ring. I then carefully cut the masking tape with a scalpel and make sure it adhered on either side of the cut.

I Then repeated the process at f11 placing the tape on the other side of the factory distance marks.

These home made marks are so easy to use and very precise. You can gauge the alignment on both sides of the tape and the edges are sharp. Only downside is that you have to redo the process every couple of months when the tape has come off.

[jatrax]

These home made marks are so easy to use and very precise. You can gauge the alignment on both sides of the tape and the edges are sharp. Only downside is that you have to redo the process every couple of months when the tape has come off.

Good idea!

[pathdoc]

On my da21 ltd I've made my own markings. The etched in ones weren't accurate enough and I only need f8 and f11 markings. So I put my camera with aperture f8 on a tripod measured out the theoretical hyperfocal distance (can be calculated on various websites) from the crossed 0 on the body to a high contrast target. Used the autofocus (live view) to focus on the target. I then put a thin (4mm) strip of masking tape across the barrel/focus ring. I then carefully cut the masking tape with a scalpel and make sure it adhered on either side of the cut.

I Then repeated the process at f11 placing the tape on the other side of the factory distance marks.

These home made marks are so easy to use and very precise. You can gauge the alignment on both sides of the tape and the edges are sharp. Only downside is that you have to redo the process every couple of months when the tape has come off.

I wonder if dcshooter couldn't arrange a more permanent solution for you.

[clackers]

With AF, it is better to just put AF on a spot half-way to infinity, use an aperture like f8, and hope for the best.

One-third. ☺

[pathdoc]

Last I checked, one third of infinity was still infinity. Do you mean the gauged distance to the far horizon, or have you some more precise measure in mind?

[BrianR]

Ok, I happen to have on my desk a Pentax-A 20mm f/2.8 and a Pentax DA 21mm Limited. Perfect for this I would think!

Using the extreme of f/22:
Pentax-A 20mm shows in focus from infinity to 1.1ft
Pentax DA 21mm shows in focus from infinity to 1.8ft

...

Distances approximated as honestly those little marks are kinda hard to interpret. And there is nothing on the DA 21mm to even guess at f/8

Up to the marks being hard to interpret, this looks in line with rejigging the scale on the DA lens for the aps-c sensor. Thanks for checking

[clackers]

Last I checked, one third of infinity was still infinity. Do you mean the gauged distance to the far horizon, or have you some more precise measure in mind?

I will be sending you 100% of the fee I received for my post, Pathdoc! 😁

One third "into the scene" I've heard it phrased as.

The takeaway is that depth of field isn't symmetrical before and after the focus point.

[Na Horuk]

I will be sending you one third of the fee I received for my post, Pathdoc! �� One third "into the scene" I've heard it phrased as. The takeaway is that depth of field isn't symmetrical before and behind the focus point.

Yes, this is correct. The DoF is not 50% in front and 50% behind the focused distance, and it is generally accepted that in the field you can get away with focusing one third into the distance and get the subject and a lot of stuff in front of the subject in focus. This is a rough rule from the film days and it works okay, but its not as precise as the idea of zone focusing and hyperfocal.
So lets say you want to get mountains at the horizon in focus and as much in front as possible - you focus one third in and you get the mountains and as much foreground as possible. If you focus directly on the mountains, you would get much less area in focus. But of course things like lens focal length, chosen aperture and medium (film, sensor) play a role

Here is an interesting article that mentions this third in rule and how it relates to hyperfocal:
http://improvephotography.com/769/hyperfocal-distance-wide-angle-lens-depth-of-field/

[stevebrot]

My personal philosophy is that using hyperfocal distance is a carryover from the manual focus era, where you wanted to shoot fast and be reasonably sure of a decent result. I personally see no need for it with AF lenses in my photography;

Yep, only useful if you want to shoot fast and not be held prisoner by the AF system or the MF system for that matter. Using the hyperfocal or some other form of zone focusing has been stock technique for street photographers since Cartier-Bresson and continues to have the same utility today.


Steve