Tuesday, July 29, 2014

Print Sharpness Vs. Image Sharpness

I used to write with a fountain pen. With some paper the ink would bleed from the original line, perhaps as much as an 1/8 of an inch in diameter on cheap paper with a loose weave - for example, newsprint. The same thing happens with solvent based felt pens writing on newsprint flipboards.

Well, the bad news is the same thing happens with inkjet ink. Yes, it dries fast, but in the second or two before it does, the ink can spread, and the very surface that is designed to hold a lot of ink and therefore make rich prints, can also result in more spread of the ink.

So, it turns out that how sharp your prints look is a function of the individual brand and surface of the paper. Another brand in a similar surface may be significantly less or more sharp.

I recently switched (for routine printing) from the very expensive and no longer made Ilford Galerie Gloss Baryta paper, to Inkpress luster. I quite like the paper, but I think I'm taking a hit in print sharpness. Oh, not a lot, just enough to annoy me, especially in smaller prints.

To some degree this can be compensated for with output sharpening. I used to do this routinely with matte paper but had stopped when I went to the Ilford paper, but looks like I'm going to have to restart it. I was using Photokit sharpener output for prints.

Pentax DFA 25 mm. on Pentax 645z

The whole scene

  
 Centre crop - click to open in new window at correct size

 
 2/3 of way out to upper left - remember to click for actual size

3/4 of the way to upper left - and click
  
extreme upper left - yet again

So, this is f8 in a real subject, not a flat plane. Lightroom used its profile for this lens to correct for distortion and I had to add some extra purple defringing so this is what one would actually have to work with. Clearly the corner is not great, but remember this is a tiny part of the picture. I made a print, 41X55 inches, or at least the corner thereof, and the 13X19 print of the corner is sharp from 6 inches in - this looking at a 5 foot print from 10 inches. Do I wish the corner was a bit sharper, sure, but I can live with it. In practice, this means that with the Pentax 645Z I can make a 41X55 print that looks as good at the same viewing distance as a 24X36 inch print made with my Canon 5D2 and 17-40 at 17 mm. - so almost double the linear dimension (24 to 41). Essentially that's what I was looking for.

This is 100% even without clicking, but you see more when you do, of the same corner, but at f16, and a little bit more sharpening in Lightroom (70, .8 instead of 50, .7), also a bit more shadow recovery.













Monday, July 28, 2014

How Much Does Focus Blending and Stitching Cost In Sharpness?

This one is hard to quantify, but I think I can say that the answer is quite a lot. If I want to make a square picture and use a 2 - 3 image stitch to do so, it is definitely better than cropping a single image, but truth is every time we morph our images, to correct lens disortion, or perspective, or to stitch two images together, we lose a little resolution, perhaps as much as a third, which would be the equivalent of going from primes to a zoom, or a top zoom to a kit one - and really only an issue in really large prints or on screen at 100% (as per previous article about lens quality).

Remember that when stitching shots made with wide angle lenses, there is a lot more morphing and stretching of the image and pixels than in an image stitched from a longish lens.

My feeling is that focus blending also loses a fair bit of resolution. First the images have to be stretched compensate for size changes as you focus (true of all lenses but oddly not always in the same direction in zooms). Then the sharpest bits have to be tested for and gathered, and though I don't know, that may cost further resolution.

Think about the following worst case scenario:

You are using a wide angle lens to do an even wider stitch panorama. The lens has some distortion so in processing the images ready for stitching, Lightroom corrects the barrel distortion common in wide angles. Then the stitching programme does it's on pinching and stretching to make the images stitch properly, and then a whole lot more stretching to compensate for perspective distortion (unless you select cylindrical view and accept curved straight lines). Depending on how wide the lens is and how long the panorama, this might be as much as a 100% stretch, cutting resolution at the sides of the print by as much as 50%.

One way to avoid this cost in stitching is to use shift lenses, or a shifting back. Here the only limitation is lens quality at the larger image circle edges. For my Canon 24 ts-e lens, it shifts beautifully and a stitch that doesn't use image morphing can result in extremely high quality results. Lesser lenses do engender more loss at the edges then you have to test to see whether a camera swing type stitch is better than a lens shift stitch.

Bottom line, the wider the angle of lens, the more difficult it is to stitch, and oddly the same thing applies to focus blending as well where perhaps due to the complex nature of the wide angle lenses to minimize distortion in the first place, simply scaling images does not make them match all across the image and detail is lost.

So, with all of this, is there a role for stitching and focus blending? Absolutely. Like I started with, the square image from a crop doesn't hold a candle to the two image stitch, it's just that the two image stitch isn't quite as good as you think it should be.

The best way to think of it is that stitching is like switching to a larger format camera, with a poorer quality lens.

There is one situation where more pixels, even if not of the best resolution still makes better prints and that's in really big prints. This takes us back to the days of film where as one enlarged the images, they would gradually become less sharp, but there was no sudden cliff of lost quality. Now that most shoot digitally, the cliff is there, where sharpening becomes visible and pixellation becomes problematic. This seems to be true regardless of the strategy to make the really big prints - enlarging before sharpening or after, using this plug-in or that. The greater the number of original low noise pixels, the better, which usually means a larger sensor, not breaking up the current sensor size into smaller but more numerous pixels.

This is one reason for my happiness with the Pentax 645Z. It can take more editing, more stretching, more blending or stitching than cameras I have used before, and why, though micro 4/3 can make lovely images, they don't hold up in editing as well as images made with larger formats. If you don't do a lot of blending and stitching and editing and manipulation and perspective correction and lens correction, then the results can be wonderful.

I guess you could say I tend to stress my image files, and the more information there is to start with, the better the result.

Whether anyone should be torturing images like this is whole other matter and a subject for another day.

Lenses For The Pentax 645Z

Lloyd Chambers has just commented that he wouldn't purchase a Pentax 645Z because of poor and inconsistent lens quality (and quotes his testing on the 645D, as well as with the 25 mm. on the 645Z).

My experience with the lenses for the Pentax has been different - centre resolution has been just fine, and corners have been good across the board (35A, 75A, 120A, 150A, 200FA, 300FA) and adequate on the 25 (entirely expected given the nature of the lens).

Remember two facts though - first Lloyd is comparing the Pentax with its available lenses, to the Nikon D810 with the best Zeiss glass, all primes, all expensive, all manual focus. That's fine, but doesn't reflect the real world for most who feel that the whole point of something like full frame digital slr's is to have auto focus and perhaps IS and zooms. Second, I looked into Pentax 645 glass before making purchases and knew pretty much what I was getting into - I settled on primes (not the zooms that Lloyd felt were so so), and avoided focal lengths that had proven less than stellar (45 mm. and oddly, the newish 55), and with the exception of replacing the 200A with the 200FA, have been happy with my choices.

Shutter shake was an issue for longer lenses, not the lens quality itself when Lloyd did his 645D testing, and I too am having some shake issues. It isn't clear yet if this is the shutter or as I hope, the two second mirror up self timer that ideally should be at least 4 seconds. Oddly, when on the weekend I tried switching to the 12 second self timer, I lost mirror lockup. Next weekend I'm going to try the separate mirror lock up control PLUS the 12 second self timer and see how that does. I'm fairly optimistic this will fix the problem with the 200 and 300 mm. lenses as the shake I have seen is in random directions, not that of the shutter movement, and also based on my experience with the Canon 5D3 and Nikon D800e where I know damn well that 2 seconds was not enough to dampen vibrations with the 70-200 lens despite a good tripod, good head and good lens collar.

The 25 mm. Pentax DFA isn't ideal, but neither was the Ziess 15 nor the Nikon 14-24. I suspect I could get close to perfection with a non retrofocus lenses for technical cameras and a separate medium format back - for a minimum of $25,000 for a one lens outfit. That isn't going to happen. I have made several images with the 25 that I could not have made with longer lenses, not without stitching anyway and given I was focus bracketting, that would have been cumbersome at the least.

How Far Apart Are Mediocre and Superb Lenses?

There are two ways to look at lens quality - what can you measure and test, and what can you see in prints. They 'ain't' the same thing at all.

For example, I made good use of my Sony A6000 on holiday, and the most used lens was the 55-210 - which according to all the usual test sites (photozone.de, slrgear.com) is mediocre. Yet, I have made some lovely images with this lens, and sharpness to me, in the print was perfectly fine. I even tried it on the A7r before selling that camera, and it wasn't bad, but tried removing the baffle to get even wider coverage on the big sensor camera and definitely the edges are poor, but it was never intended for full frame sensors so can hardly be blamed for that.

It's so small and light that it's a perfect match for the A6000, and one of the things that put me off the A7r in the end was that with my 70-200 Canon (that was noticeably sharper than the new Sony 70-200 even in prints) the camera ends up huge.

Issues of quality apply to all formats. Theonlinephotographer recently published an article on lens quality - how to use a lens to it's best, and how to stress it and it makes good reading.

An example of stressing a lens is stopping down well beyond the start of diffraction. Peruse any photo magazine that features landscape and you will find plenty of examples of f22 on a 35 mm. format wide angle - well within diffraction, and when viewed on screen at 100%, clearly showing that the benefit of increased depth of field did not outweigh the fuzziness introduced by the small aperture - but the magazine print, some of them two page spreads, look fantastic. Likewise 13x19 prints show the same thing - what is seen on screen isn't shown in print.

I started to notice this when I went to 20+ megapixels - what was clearly out of focus on screen looked fine in normal sized prints. It's all very well making test crop sections from really enlarged prints, but if you never actually make the uncropped huge print, what you are testing isn't reality.

This is a common phenomenon - just think of cars that handle beautifully at 150 mph, but fortunately are never driven at that speed, cars that cost a lot so they can do wheelies and burn rubber, but you don't because the tires are expensive, and besides, you grew out of that when you turned 21 (ok, maybe 40 for some).

Consider too, the subject matter. A lens that is sharp in the centre but has weak corners and even edges will be fine in portraits, sports, news, streetshooting, and just about anything other than distant landscapes and architecture.

We also need to consider that a superb lens on a small format will not look as good in a large print as a medium quality lens on a larger format, everything else being equal.

Lenses like the Zeiss Otis are mostly about being extremely sharp, corner to corner, wide open, and at this the lens has no peer. But how many of us need corner to corner sharpness at f1.4, or for that matter, the high contrast this lens has wide open. Often 1.4 is for people pictures and a bit of reduced contrast isn't a bad thing, and how often are the corners in the same millimeter deep area of focus anyway?

Bottom line: modest price primes and top quality zooms do a pretty decent job.

Sunday, July 27, 2014

Pentax 645 and 200 mm. FA Lens


This is a 100% crop from an ISO 800, f7.1, 1/250 sec. handheld shot, making a 20X27 inch print at 300 dpi. My thinking is that if 100% looks this good.... Testing at the corners is yet to be done though in casual images, there might be some forward focus but just as sharp.

Friday, July 25, 2014

Backing Up

Over the years I have tried a variety of backup strategies, from two different Drobos, to using Time Machine (Mac backup that backs up all the time so even a file erased earlier today can be recovered), to various external drives.

Drobos were slow, and given they were backup, the fact that they back up redundantly was somewhat unneeded, and given they stay plugged in at home, don't solve the problem of a power surge or fire.

Time machine has proven handy in the past when something got corrupted and I needed to go back to before the corruption, but the cost in slowing down the computer has been unacceptable.

All methods have had their problems. Taking the time to find all the raw files to back up onto one hard drive is problematic, though easier since I started using Lightroom, but not for the old files.

Today I have started what I hope will be both easy and fairly strong insurance against failure.

I picked up a hard disk caddy, and am now doing a 1:1 backup of each and every hard drive that is used as primary storage for my images. No more shuffling files and storing multiple drives onto one backup. As long as the receiving drive is as big or bigger, no sweat. I plan to do two entire sets, one for home, one for the office. The home set will be backed up in the future on a regular basis, the office set probably no more than once a year. Both sets of hard disks will be sitting unused and unconnected and at low risk of loss.

So far the process is slow, so it's something I'll run overnight for each one.

I might still consider time machine the main few hard drives but not for all the peripheral ones (of which there are half a dozen, on top of the four in the desktop Mac Tower, and only if it doesn't get in the way.

Is this ideal backup - absolutely not - I could lose an image from the last few months in a catastrophic failure, but I have Lightroom set up to make duplicates of all images as I dump the memory cards, so the worst I'd lose would be an edited image of less than three months age - that's something I can live with, especially as often with my favourite images, they get saved multiple times during the editing process, and in conversion to TIFF for large scale printing, and with toning, etc.

The big thing is it's better than what I have at the moment, which has been piecemeal for the last couple of years due to a variety of technical glitches saving to raid machines.

So, simple, redundant, and doable, that's what I'm looking for.

Why the Pentax 645Z Makes Sense For Me, But Maybe Not You

I've been reading the dialog between Diglloyd and Ming-Thien and thought I would respond to the issues they raise relative  to the Pentax 645z

You have to be aware of my situation.

1) 99% of my photography is on a tripod.
2) All of that is live view, manual focus, magnified view.
3)95% of my photography with the 645Z is done at f11, or sometimes f16
4) Although I don't sell a lot of prints, I do get requests occasionally for 6 foot wide prints - I need the most pixels I can carry.
5) I'm 64 and have a  bad hip - I'm not going to be hiking more than half a mile (the distance into Jura Canyon) any time soon, so +- 5 lb. carrying weight isn't relevant.
6) 95% of the photographs I make take 5-20 minutes to set up, find exactly the right position, get the right height on the tripod etc. so a little extra time to set the camera itself is moot.
7) the few times I need a faster camera, I generally know it before I leave the house and can take a more appropriate camera. I'm debating whether to hang onto the 70D because it will take my remaining Canon 70-200, the 400, and my two ts-e lenses, the 24 and 90, or more likely wait for the new Canon. If it really is good, then I might get that, if not perhaps the price of the 5d3 will drop and I might be able to pick up a used body.
8) for travelling with my wife, the A6000 is so light and compact and handy and did such  a good job in Newfoundland, it's going to work well for some time to come.

Yes, I did shoot those horses the other day, and the Pentax 645Z did just fine, hand held, with the 300 mm. lens, for making a 20X27 print.

Consider too, what I was looking for:

a) a camera that mounted lenses the right way - and it's not just the lenses but every rear lens cap too (perhaps you can forgive Nikon when you remember the Japanese drive on the left side of the road).
b) I needed a fully functional live view, at open aperture - only Canon has that.
c) I've come to live the tilting screen on the A7r and the 70D. Yes, I'd prefer both tilt and swing, but tilt covers 90% of the situations, not the 50% you'd expect, so it's a hell of a good start and remote viewing via my iPhone may solve the rest (I have a flu-card on order).
d) I didn't like the button and control layout on the A7r and much prefer the situation with the Pentax.

And don't forget, I had already acquired an almost full set of lenses for the Pentax three years ago when I came close to getting the 645D (at about $300 a lens) which can still be done.

So, with that background, my decision seems almost a no brainer - even though I can imagine some situations where the Nikon D810 might be a better choice given the wide range of great and fast lenses for it - the Sigma 35 and 50, the Zeiss 15 and 21 and wide variety of long lenses. Yet, the Nikon zooms aren't that great - the 24-70 is mediocre at 24, the 70-200 f4 good but not outstanding at 200, the 80-400 (new) good up to 300 mm. and fine in the centre at 400, but not for landscapes, great for wildlife though (that I don't generally shoot).

So,for me, for now and the next few years, the Pentax 645z makes good sense. Whether it would for you will depend on your needs, desires, and circumstances. I'm hoping this explanation might help you make your decision.

Tuesday, July 22, 2014

Pentax 645Z F Stop Setting

I note on the PentaxForums that Royce Howland, fellow Calgary photographer  has discovered a possible glitch in the Pentax, in that he can't reliably use the f stop ring on some lenses when in manual exposure setting. I had not discovered  this because I always put the lens into A mode where the camera sets the f stop, after all the camera comes with front and back dials specifically for the purpose, but still, if you can do it, it should work.

When I tested my camera, the same problem happens - for some odd reason, when in manual mode and setting the f-stop on the lens, the camera thinks it is two stops wider, and that gap stays as you change f-stop. This only seems to happen with FA lenses, not the A series manual focus lenses, and not the new lenses that of course don't have f-stop rings anyway.

For me, it's a non issue, just something for people to be aware of - use the body to set f-stop, lens aperture set to A.The proper aperture is set and recorded.

Sunday, July 20, 2014

Editing Turner Valley 645Z Images


 The colours of the above image were not harmonious and the image shouted for a black and white conversion. Given the antique nature of the subject, it seemed sensible to apply a toning. I used my usual browntone made by applying a fill layer of solid colour and converting the blend to colour, with adjustments to intensity across the brightness range via the blend detail window (double clicking on the layer). I wasn't quite happy with it and having this evening looked through Roman Loranc's wonderful book of photographs in which he uses a neutral black but toned mid and light tones, I decided to try adding a saturation level, with a -76 adjustment to saturation. I then double clicked on the adjustment layer and moved the right hand (highlight) slider of the output image to the middle, thus removing the desaturation from the light tones. I then used the opacity slider for the layer to reduce the desaturation effect overall to 70%, leaving jut a little richness to the shadows and softening the gradation of colour.



I quite liked the web image but my print of this photograph looked week, the highlights lacking detail, the port quite dull, and the backdrop rather flat. About a dozen adjustment layers later the port had some oomph, the shadows some depth, and the highlight silver some richness.

I don't think I'm finished with the editing here. I think to right of the port could be a tad lighter, probably using a curve in which the white point is moved to the left, rather than just a lightening curve. but first I'm going to live with the print for a few days.

One thing I'm delighted with is that these files do stand up really well to editing. It does seem that the larger and cleaner the original file, the better edits look. The Nikon D810 is out and it fixed most of my frustrations with the Nikon, and early testing suggests the images will be great, but I have absolutely no regrets about my purchase of the Pentax 645Z, the most comfortable I have felt about a purchase in a long time.

More Images From Gas Plant








Images From Turner Valley


This was with the 300 mm. lens, two images blended, though in hind sight I really needed 3 to get the nearest part of the fibreglas in focus.




This was shot with the 75 or maybe the 35 and below is a 100% clip from somewhere in the middle. I'd love to see a six foot print of this image.



Shot with the 120, aiming upwards, perspective corrected in Photoshop, Command A to select all, Command T to transform, and Command Drag to stretch the corners to correct perspective and trim exactly to requirements.

Another Day With The Pentax 645Z

I photographed about four hours and by the end the camera battery was indicating low but not out - still functioning fine. I had used live view for all the images, and many were 30 second exposures inside one of the Turner Valley Gas Plant buildings, all the windows boarded up, light supplied by one large door in  a very large building. I used the 25, 35, 75, 120 and 300 mm. lenses.

To my surprise, the images from the 300 look great - very sharp. This might have to do with the 30 second exposure eliminating shake, also no wind indoors. Outdoor images were inconsistent, some sharp, other very definitely showing movement. I know that when I was using both Canon and Nikon, 2 seconds wasn't enough to settle movement after pressing the shutter and I'm looking forward to getting an infrared remote for the camera. Clearly more testing is required, but it's nice to know the lens itself is fine.

The camera worked perfectly, with no quirks that I could discover. I'm still learning how far to the right I can push exposure. At the moment I'm being pretty careful not to go well into blown highlights just in case, and knowing I can dig into the shadows without problem.

My impression is that while resolution may not be that much higher than the D800e, it's easier to get high resolution - the Nikon could do it, but not consistently, even in similar conditions, and frankly that's a huge advantage for me.

When checking sharpness of an image already made, you can scoot around the magnified image quite quickly. When doing so in live view before the shot, it's fairly slow - not an issue for the kind of work I do.

Focus blending is working well, using Helicon Focus, and I made my first images today that will need to be stitched - which is perhaps a bit silly but the lens nicely fit the vertical part of the subject and it just seemed natural to then swing the camera.

I did wonder how badly I'd miss my zooms, after all my 70-200 has always been my favourite lens, both in Canon and Nikon. To be honest, I didn't even give it a thought till now, after the fact. Sure I did more lens changes as I set up scenes - but that's at least as much lack of familiarity with the angle of view of the specific Pentax lenses and already is improving.

I worry that the battery compartment lock seems flimsy - a thin tab that has to be lifted up, turned 90 degrees and then pulled to open the door. It would be very awkward in gloves. I'm going to be careful with this.

I have to be a bit more careful clamping the camera to the tripod head The small square Really Right Stuff plates are great for not getting in the way, adding bulk or weight to the camera, but as the camera is much larger than the plate, I seem to be spending more time checking to be sure the plate is really seated in the clamp before letting go  - but this is mostly to do with the size of the camera blocking the view of the clamping, not the smallness of the plates and I wouldn't want larger plates. It's even worse when I use Arca Swiss style plates on a view camera. For that size, I actually prefer the safer and much larger plates from Manfrotto, but I wouldn't want to put two of those on the Pentax.

One thing that has to be considered with Pentax is the size of the company and the rate of development, though if you think of how long people have been waiting for a new 100-400 Canon zoom, or a 400 5.6 with IS, maybe I shouldn't worry too much. I do have the sense though that the camera and lenses have to work for me now, not from some future possible development. For my style of photography, the Pentax and its current equipment are perfect and I have no sense that I'm limited waiting for further developments. This won't be true for others, who might need leaf shutter lenses, or tilt shift. As to this latter, correcting perspective in Photoshop is so easy that shifting isn't really needed (and with the high pixel count, using shifting to stitch more pixels isn't important, and tilting has largely been replaced with focus blend, which is, after all, a lot more flexible being able to cope with 3D subjects, not just flat planes.

What if the company itself disappeared? People used Contax medium format for at least 10 years after the company went bye-bye, so again I don't see this as a huge issue and the fact that Ricoh can release such a great camera at this time speaks well of the company. The 645D was successful despite its limitations, the 645Z could be huge for the company.