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11-12-2018, 02:02 PM   #1
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Orange Writing on Lenses

Someone teach this idiot why my SMC-A 24/2.8 lens has certain values on the lens in orange ink rather than white? F8 is in orange and then the Focus Ring has 7ft and 2.2m in Orange, what gives?

Am I to take it that throwing the lens into F8, lining up the focus ring to those 7ft/2.2 markings will mean that anything further than 2.2m away from me will be in acceptable focus/sharpness? Does it essentially become a 'street photography' like 'snap' shooter settings?

Up till now I haven't really tried portrait work with this lens, or rather group family shots etc. It's been my landscape lens and so I typically have the focus at Infinity or a tad back from that (I think I get a tiny bit more sharpness dialled a mm back from infinity etc). What I find nigh impossible is to really nail focus at f2.8 etc with people with this lens, the DoF feels stretched and very shallow. It's what's prompted me to consider looking for a FA20, FA24 or FA28, just so that I can get assistance with those wider aperture shots on people.

However I am overall pretty pleased with the performance of this lens.

I have some family shots to take this weekend, location shoots etc where actually grabbing a decent amount of detail of the background and where the peeps are is also important. I will likely be shooting at one location with plenty of light, so I could feasibly manage F8 with still grabbing ISO 100-200 along the way (and acceptable shutter speeds to boot). I'm wondering if I can just lines those values up, distance myself a good 2.5-3m back from them and snap and capture the shot without worry?

I think I'll still avoid this lens as a wide aperture portrait thing, it's just really hard, and people also move. But if I can think of it as a landscape lens + 'group shot without much bokeh' then that's actually not a bad thing and increases it's uses.

TIA!

Bruce

11-12-2018, 02:15 PM - 1 Like   #2
dms
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If you check the hyperfocal distance for 35mm film (FF) at f/8 it is about 7 feet or about 2.2 meters, meaning everything from half those values to infinity will be in reasonable focus (assuming you print about 8"x10"). The fact that it is in color I believe is saying that (f/8) is where the lens performance is best--but if that is correct and what best means perhaps others can say more.
11-12-2018, 05:07 PM   #3
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Yup hyperfocal. You place the infinity mark on the far line and hyperfocal will be in focus.
11-12-2018, 05:35 PM   #4
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It's a really cool feature of that series of lenses.

11-12-2018, 05:38 PM   #5
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The orange hyperfocal markings are on many Pentax manual focus wide angle lenses. It is sometimes a clue when you are squinting at a terrible eBay photo that one of the lenses might be worth something.
11-12-2018, 05:50 PM   #6
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But if you pixel-peep, it doesn’t work on a modern camera.

The whole scheme assumes an approximate image size and viewing distance.

Modern gear can take you much farther, so you may need to fiddle around to see how far you can realistically go.

-Eric
11-12-2018, 07:38 PM   #7
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I might test mine out later today.

11-12-2018, 10:04 PM   #8
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As noted above, the marks are intended as "box camera" settings appropriate for street photography or similar with 35mm film and are close to the hyperfocal for that format.* For APS-C, the hyperfocal for f/8 is at about 12ft with a near limit at about 7ft.


Steve

* Calculated hyperfocal for 24mm on 24x36 FF at f/8 is 7.9ft with near limit at 5.3ft.
11-12-2018, 10:26 PM - 2 Likes   #9
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QuoteOriginally posted by BruceBanner Quote
What I find nigh impossible is to really nail focus at f2.8 etc with people with this lens, the DoF feels stretched and very shallow. It's what's prompted me to consider looking for a FA20, FA24 or FA28, just so that I can get assistance with those wider aperture shots on people.
There are reasons why traditional ultra wide-angle lenses are seldom used for portraits, even for groups, and you have happened upon a couple of them. Yes, fine focus is very difficult, even with viewfinder focus aides. Another thing that works against one is the small axial movement needed to cover the range from MFD to infinity. Even with very fine helicoid pitch, it is hard to place the focus ring properly. AF lenses might work better except that the same factors that frustrate manual focus are also at work for AF. As for DOF...Contrary to popular belief, DOF with a wide angle lens is not deeper for a given reproduction ratio. Filling the frame with a face at f/2.8 on a 24mm lens will give you similar DOF as doing the same with an 85mm lens at f/2.8 with the added unpleasantness that the 24mm will throw in a bit of perspective and volumetric distortion due to simply being uncomfortably close.


Steve

Last edited by stevebrot; 11-12-2018 at 10:31 PM.
11-13-2018, 03:54 AM - 2 Likes   #10
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As it is a very common misbelive, I would like to add some comments to steves remarks about DOF.

I have to add, I did not find out the following on my own, it is form the (german) wikipedia. But from my practical experience it is true.

First of all as Steve said, the common believe, that for shooting portraits with shallow DOF you need as much focal length as you can get, is completely false. Do not belive your beginner's book!

As Steve already told: For a given reproduction ratio (remember portrait!), the DOF mainly depends on the aperture used. For a shallow DOF you need something with an aperture of 2.0 or 1.7 or wider. This is what makes the 1.7 50 mm a perfect basic portrait lens.

And here comes the but. This is only as long as the distance to your model is not more than a quarter (I would say a bit more, but thats the wiki) of the hyperfocal distance as given through the focal length and aperture. As the hyperfocal distance of a wide angel lens is much shorter, than that of a normal or telephoto lens, you will get a sharp background sooner as you like.

Now let's talk about shooting portraits with a 24 mm. If you take a picture of your models head only and you have a 24 mm with 1.7 aperture there will be no great difference in the DOF compared to your 50 mm. But as steve points out you will not do that, as a nose the size of a potatoe compared to the rest of the face is not what you want to see in a portrait. Thus you take half a step back with your 24 mm and include the upper part of the body. You are now 1 meter away and you will have a DOF of about 1.75 meter with your 24 mm. With your 50 mm from a distance of 1,5 meter you will have a nice picture (less of the person) and a DOF of about a foot length.

Sadly I can not afford a 24 mm with 1.4 aperture. And with an aperture of 2.8 and 1 meter away from my subject I will have a DOF of 17 meters, i.e. nearly to infinity. A 50 mm with aperture 1.7 has a DOF four feet at the same reproduction ration.

But why do all the people tell you, you need more focal length for shooting portrait? Because the longer the focal length, the farer the hyperfocal length, which means telephoto lenses do still have a shallower DOF, when your subject is farer away. If you want to have a shallow DOF and a picture of a complete person, be sure to bring your 135 mm 1,4 around (OK, a 85 mm 1.8 might do it).

And here is a good reason to buy your long awaited full or even medium format camera. For the same reporoduction ratio and same distance to your subject you need more focal length on the larger format. And that gives you a shallower DOF. Larger format = less DOF.

Last edited by Papa_Joe; 11-13-2018 at 04:04 AM. Reason: typing errors
11-13-2018, 08:31 AM   #11
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QuoteOriginally posted by Papa_Joe Quote
But why do all the people tell you, you need more focal length for shooting portrait?
Working distance.

Subject isolation using background blur is a happy side-effect, but not the main reason. If the lens is close to the model, the laws of perspective dictate an unflattering exaggeration of facial features. Want a big nose, ear, mouth, and/or chin? Shoot close! If a group setting, the nearer subjects will appear much larger than those next to them, depending on how the group is arranged. This effect may be worked to advantage if one wishes to place emphasis on an individual, but is usually not desirable.

Of course, the other advantage to greater working space is the comfort of the subject. A head shot with a 24mm lens on 24x36mm FF calls for the subject to be 40 - 50 cm from the lens. A professional model might not mind, but most of the rest of us prefer not to feel the photographer's breath on our face while sitting for a portrait.

QuoteOriginally posted by Papa_Joe Quote
Larger format = less DOF.
This is so very true, despite being endlessly disputed in online discussions. A few minutes shooting with a medium or large format camera is usually all it takes bring home why there are no "fast" medium format lenses.


Steve
11-13-2018, 09:00 AM - 2 Likes   #12
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QuoteOriginally posted by BruceBanner Quote
Someone teach this idiot why my SMC-A 24/2.8 lens has certain values on the lens in orange ink rather than white? F8 is in orange and then the Focus Ring has 7ft and 2.2m in Orange, what gives?
This is from the Pentax "A" Series lens manual:

Phil.
Attached Images
 
11-13-2018, 10:37 AM   #13
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QuoteOriginally posted by TwoUptons Quote
But if you pixel-peep, it doesn’t work on a modern camera.

The whole scheme assumes an approximate image size and viewing distance.

Modern gear can take you much farther, so you may need to fiddle around to see how far you can realistically go.

-Eric
I would question your conclusions about modern gear taking us further, but you are right about image size and viewing distance. Apparent sharpness depends entirely on the resolving power of the human eye + viewing distance. One would expect to stand further away from a 16 x 20 print than from an 8 x 10 one. If you view the former at the same distance as you would normally view the latter, apparent depth of field lessens in the larger print. Pixel peeping is meaningless in this context unless you stand away from the screen at a distance that adjusts for the image size on the screen when compared to the print size.
11-13-2018, 11:40 AM   #14
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QuoteOriginally posted by gofour3 Quote
This is from the Pentax "A" Series lens manual:

Phil.
I like the wording, "Snapshot marks"


Steve
11-13-2018, 12:03 PM   #15
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So I'm still a little confused (surprise surprise) over the blurb;

"Focus will be sharp for all subjects located from about half of the red marked distance all the way out to infinity without any adjustment."

So with the 28/2.8, does that mean when choosing F8, and lining the orange markings up (10ft/3m), that any subject standing 5ft/1.5m (half the distance) from the camera/lens would be in focus (and then out to infinity)?
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