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04-21-2015, 09:03 PM   #1
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645Z + FA 645 55mm: Sharpest f-stop at f8 or stop down? Hyperfocal issues....

Hi All,

Pardon the somewhat obscure thread title.

Just came back from an awesome shoot in Death Valley. Working on getting better at landscapes and really want to get everything in the shot in focus. Did a series of focus tests (shot against a target) and determined that on my 55mm lens, f8 is my sharpest stop. Images look the sharpest there. At f22, diffraction comes into play and the images look soft to me.

So I shot a LOT at f8. And I think I'm literally focusing on the wrong thing. The center auto focus point. Tried live view but couldn't get everthing in focus there.

So:

1) Should I be shooting landscapes at my sharpest aperature (f8) or stop down to f10 or f16?
2) Read up on hyper-focal distance calculations and determined (from dofmaster.com) that if I focus 25 feet from my lens, everything from 12.5 feet to infinity will be in focus. Is this a good strategy? Should I just set the camera to manually focus at this distance and crop out the first 12 feet of the shot in post?

I know I'm covering a lot of ground here but if you are shooting a landscape, how are YOU getting everything in sharp focus? Focus stacking? Or fully understanding hyper-focal ranges and circles of confusion?

Thx muxh!

ps- attached is small jpeg right out of the camera.... no processing or sharpening....

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04-21-2015, 10:10 PM   #2
dms
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Medium format is tougher because depth of field is less, and thus a greater need for more lens movements (e.g., tilting lens), but the questions you ask are ones you face with most formats, and there are no hard rules. As Ansel Adams describes it--visualization is required--to see the picture as you intend it to look--and if you do this the (answers to the) questions of what is to be in focus and what not, and how important DOF is, what size print it should be, etc., all follow.

But specifically about zone focusing--it (and especially the hyperfocal distance) is a very important tool--as the image in the viewfinder, ground glass, camera back, etc. will not fully convey this information. After a while and depending how large you print/view you may alter the table values, but that does not reduce its usefulness. If your lens does not have depth of field markings I suggest marking down at least the hyperfocal distances for the lens(es) and fstops of interest. I memorize a few of them (notably for 28mm FL and f/11 and f/16 for FF and cropped 35mm sensors) and have more extensive list of them written on my lens hoods.

The photo you include is taken with frontal light which is very harsh and lacks color--which is likely exactly what you wanted--but it also seems to lack any specific reference to anything in the foreground or background, or a relationship in line or form between them.

Maybe the photo could have focused critically on one (of what I think are) dried up vegetation. The background mountains would then be out of focus--and the focus (dead plants) would fit in the dry/parched landscape. Or perhaps the photo says exactly what you meant to say--no more or less; but then why crop out the foreground? So in the end I am not sure what you are asking vis-a-vis the photo.

If your point is that you cannot get it all in focus--you are right--but even if you could would you want to? (Actually re-reading your post that is the question.) I would think a small fstop (f/22) would not have significant diffraction effects at the size you are showing here and in a 8"x10" print--and you don't need to print larger to make your statement. If you do want more in focus a tilt shift lens on a smaller format or a true view camera in a larger format are possible--but you need to practice your craft more first. Maybe just accept that there are focus limits and work with it.

Last edited by dms; 04-21-2015 at 10:36 PM.
04-21-2015, 10:17 PM   #3
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for deep field landscapes, it may be nice to know that your lens performs sharpest at f/8, but if your foreground and infinity areas are out of focus, does that help you?
Personally, i am comfortable using f/16, for example, knowing it is softer overall than f/8, but also knowing at least the elements that matter are more in focus than they would be at f/8. I do sometimes use focus stacking and may run a stack at f/9 or f/11 (depends on range and number of images feasible of course), much wider and each stack has front and back OOF areas, which would blend poorly.
So, I think it is ok to sacrifice ultimate sharpness in order to improve DOF.

On your example posted, it appears the darker dune running through the horizontal center of the frame may have been your point of focus. At this resolution, your distant areas look OOF as do the immediate foreground. Lots of experimentation to learn each lens is helpful. good luck!
04-21-2015, 11:55 PM   #4
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The EXIF data on the image you loaded says you used the 80-160 lens, not a 55mm. If so, you're starting to get into the area of a tele in medium format and you'll be hard pressed to capture an image with sharp focus from front to infinity. As mikeSF said, don't fret about using f16 when necessary for increased DOF.

04-22-2015, 02:34 AM   #5
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As above comments state, plus...

I'm getting used to shooting at f16 again now that I'm using the Z, and that's an important aperture for any of us attempting deep focus with the Z. To some extent, problems with diffraction are overstated. Yes, you introduce some softness. But as a friend pointed out to me, that softness applies to the whole image, and that is easier to correct in PP through deconvolution, as with a program like Focus Magic. So it is possible to gain back some of the lost sharpness.
04-22-2015, 03:56 AM   #6
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Hyperfocal use assumes a number of factors, one of which is your intended output size and the distance from which the print will be seen, without this criteria, you are trying to solve half an equation.

If we were to assume that you want pixel-perfect sharpness, the COC of two pixels on the 645Z results in a theoretical ideal aperture of around f/10, but you likely won't see diffraction even at f/16 - I sure don't. This isn't especially useful though, because looking at the image at 100% on your average 27" 1440p display is equivalent to inspecting a 1.5 x 2 meter large print! Unless you actually intend to print an image that large and have people look at it from the distance you sit at your monitor, you'll get the idea now that you have a lot of leeway when it comes to whether a greater depth of field is more important than absolute sharpness in your image.

More realistically, if we were to assume a 42 x 60cm (16x24") print, and a viewing distance of 50cm, we could get away with f/32 and not see the effects of diffraction. Similarly, f/16 is enough for a 84x60cm (32x24") print viewed from 1m/3.2' away.
04-22-2015, 05:14 AM   #7
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Awesome info! I shot a ton and grabbed something shot at f8 without remembering that I swapped lenses out during an afternoon.

The photo I posted isn't a particularly good one... But it does illustrate the problem of focus.

So... I'll start experimenting with shooting at f16 .... on the 55mm prime... and worry less about diffraction... Trying to print these fairly large... Some 17X22 and up.

Last question: at f16, on a 55mm lens, on this camera, hyperfocal distance of 12.6 feet will show acceptable sharpness from 6.3 feet to infinity..
at f22, on a 55mm lens, on this camera, hyperfocal distance of 9 feet will show acceptable sharpness from 4.5 feet to infinity...


Am I reading this correctly? I realize that experimentation will be in order but trying to get my arms around what distance to actually focus at.... May try with a tape measure

All the best....

S
04-22-2015, 06:04 AM   #8
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QuoteOriginally posted by steve645z Quote
Am I reading this correctly? I realize that experimentation will be in order but trying to get my arms around what distance to actually focus at.... May try with a tape measure
This is a subject where words like "acceptable" often crop up, which means that ultimately you need to set yourself a standard that you will be okay with. For a start, you need to see for yourself when or whether diffraction becomes a problem by doing the following:

1. Shoot a landscape using hyper focal guidelines at every aperture from f/8 to f/32.
2. Resize the images to your intended output size, and crop out two sections from each image that focus on near and far details.
3. Print out a sheet of all the crops marked with the aperture used, and compare.

You now have a visual guide that you can use to determine what you think looks good. Look at the print at various distances and take note... It's a better approach than just theorizing and talking about it online.

Of course, not all landscapes or other environmental images need to be shot stopped down, and you don't always need to get everything in focus, which is where the good old 16x live view focus comes in.


Last edited by Kolor-Pikker; 04-22-2015 at 06:28 AM.
04-22-2015, 08:06 AM   #9
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This is an interesting discussion. Before I got into MF, I shot mainly with the Canon FF, using a 16mm lens, at f16, everything from 3 ft to infinity is in focus. That is a simple formula to remember. The longer the lens, the less DOF naturally.

I think as DMS says above, what is equally important is what is the end product that is desired. For me, landscapes mean large prints - at least 20X30 which will be viewed from around 3 ft or more.

With wide angle shots, you always need something in the foreground, close to the camera if possible. However, there are no really wide angle lenses for the Z yet (the 25mm is not available).

There are two apps for the iPhone I am working with right now, the OptimumCS pro and the TruDOF pro, they are a bit more detailed and useful than DOFmaster and other simple apps out there, allowing you to adjust for print size and resolution. Not sure if they will work for everyone but if you have multiple bodies and lenses like I do, it is hard to remember all the hyperfocal distances. They are a bit pricey, but given how much we spend on our equipment it may be well worth the money to get something good.

Pradeep
04-22-2015, 10:03 AM   #10
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In landscapes, composition trumps diffraction worries. Job #1 is the composition. Do keep in mind that DOF scales on many Pentax medium format lenses are optimistic. You will need to set it a bit more conservatively than what is shown on the barrel. Hyperfocal dots can be put on the zoom lenses, as I have done with mine. If you find that using f/22 is not acceptable for your usage, there are always 4x5 cameras that can do a great job.
04-22-2015, 02:53 PM   #11
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I use the "Program Line" in the menu to set DOF to deep or maximum. I use either the 25 or 28-45 which I consider both as being WA lenses and setting my DOF scale 2 stops less than the lens markings for a degree of safety, my images seem to come the way I like them with foreground and infinity in focus when I want that.

I never hear anyone talking about the "Program Line" option in the 645Z camera 4 menu. Does everyone use it set to "Auto"?

Last edited by algrove; 04-22-2015 at 02:54 PM. Reason: spelling
04-23-2015, 07:38 AM   #12
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Infinity focusing

QuoteOriginally posted by steve645z Quote



1) Should I be shooting landscapes at my sharpest aperature (f8) or stop down to f10 or f16?
2) Read up on hyper-focal distance calculations and determined (from dofmaster.com) that if I focus 25 feet from my lens, everything from 12.5 feet to infinity will be in focus. Is this a good strategy? Should I just set the camera to manually focus at this distance and crop out the first 12 feet of the shot in post?


What I have been doing for years with my Canon/Nikon is outlined in this Part 2 of 4 Shutterbug article on focusing by Harold Merklinger:


http://www.trenholm.org/hmmerk/SHBG02.pdf


If I were faced with the scene you posted, I would put focus on the distant mountains and stop down to f11 or so depending on lens if I desired front to back sharp focus. If I were faced with a similar scene but shooting 'from the ledge' so to speak where the entire frame is at infinity, I might only shoot f5.6 depending on lens (thinking of the 24-70 II here) because the lens design allows for great corner performance. Hyperfocal may give me an Nth better overall focus front to back but this is so much easier on certain compositions and results in acceptable front/back on relative smallish images.


Here's a 'from the ledge' image (infinity across the frame) from a test location I regularly take my camera/lenses to for evaluation and where I recently took my 645z to put it through its paces. I usually shoot brackets from wide open to the smallest aperture at full stops at various FLs if I am testing a zoom. This was the 28-45 @28mm f11 which I judged to be the sharpest overall aperture center to corner. I put my focus point on the street at the horizon. For testing lenses for landscape, I would suggest finding a scene like this for at least part of your testing. Edit: sorry about the IQ. I downloaded this back from Flickr. I am on my work computer and not at home. If there is a facility for viewing this at its full size, perhaps that help improve IQ.
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04-23-2015, 04:26 PM   #13
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QuoteOriginally posted by rfkiii Quote
What I have been doing for years with my Canon/Nikon is outlined in this Part 2 of 4 Shutterbug article on focusing by Harold Merklinger:


http://www.trenholm.org/hmmerk/SHBG02.pdf


If I were faced with the scene you posted, I would put focus on the distant mountains and stop down to f11 or so depending on lens if I desired front to back sharp focus. If I were faced with a similar scene but shooting 'from the ledge' so to speak where the entire frame is at infinity, I might only shoot f5.6 depending on lens (thinking of the 24-70 II here) because the lens design allows for great corner performance. Hyperfocal may give me an Nth better overall focus front to back but this is so much easier on certain compositions and results in acceptable front/back on relative smallish images.


Here's a 'from the ledge' image (infinity across the frame) from a test location I regularly take my camera/lenses to for evaluation and where I recently took my 645z to put it through its paces. I usually shoot brackets from wide open to the smallest aperture at full stops at various FLs if I am testing a zoom. This was the 28-45 @28mm f11 which I judged to be the sharpest overall aperture center to corner. I put my focus point on the street at the horizon. For testing lenses for landscape, I would suggest finding a scene like this for at least part of your testing. Edit: sorry about the IQ. I downloaded this back from Flickr. I am on my work computer and not at home. If there is a facility for viewing this at its full size, perhaps that help improve IQ.
Focus point on bridge in distance or a street I cannot see in focus in this image? I like this shot as I see it by the way, just unsure us to which street you refer.
04-23-2015, 04:45 PM   #14
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QuoteOriginally posted by rfkiii Quote
What I have been doing for years with my Canon/Nikon is outlined in this Part 2 of 4 Shutterbug article on focusing by Harold Merklinger:


http://www.trenholm.org/hmmerk/SHBG02.pdf


If I were faced with the scene you posted, I would put focus on the distant mountains and stop down to f11 or so depending on lens ...
??
04-23-2015, 04:59 PM - 1 Like   #15
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QuoteOriginally posted by mikeSF Quote
??
Yes, read this too. The first paragraph lost me. I then assiduously read the rest of the pdf. I remain lost. Nothing within it explained how focusing on infinity (the mountains) could hope to bring the foreground into acceptable focus. Not absolutely saying it can't, but really asking how on earth can it?
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