Monthly Archives: February 2013

Sensor cleaning

Has to be done.

Why bother cleaning your sensor? If you produce more than one picture in a blue moon your choice is simple. You can retouch dust blobs in your images in your favorite photo-processing application, once per image, or you can clean the sensor once and do a minimum of retouching until it is time for another cleaning. Determining whether to clean your sensor manually is a function of how many pictures you publish and of what your time is worth.


At Crissy field, San Francisco. No blobs in this sky. The benefits of a clean sensor.

While my Nikon D700 had a ‘sensor cleaner’ built in – an ineffectual mechanism which applies ultrasonic waves to the cover glass over the sensor, a process which could not wipe dried snot off a sheet of ice – it really was not much better than the sensors in the D3x and D2x when it comes to keeping them dust free. Neither of those bodies has a sensor cleaner. For a more technical reading check here for confirmation of the general uselessness of in-camera sensor cleaning systems.

Stop the lens down, take a snap and sooner or later you will see blobs in large expanses of continuous tone – skies are especially sensitive to this. And releases of oil from the camera’s internal mechanisms onto the sensor will only be spread with the ultrasonic treatment. What’s that? You think your precious Leica does not leak oil? Have you checked the road outside your house recently? Every machine which uses oil leaks it.

Forget blower brushes. These are an excellent way of blasting grit around the mirror box right onto those oily bits and represent an effective way of making matters much worse. Vacuum is the answer, not a hurricane, but sticking the hose from your Dyson or Hoover inside your silly-priced Leica M Monochrom is likely going to suck out the sensor and any dirt with it …. no more dirt, but a trip back to the Fatherland.

What is called for is wet cleaning. Well, moist cleaning.

One thing should be clear – you are not cleaning the light sensitive pixels in your sensor. Every sensor of any design, whether it has an anti-aliasing filter (most) or not (Leica M8, Leica M9, Nikon D7100, Nikon D800E, etc.) has a sheet of protective glass between the pixels and the lens. That is what you are cleaning. It’s not that fragile. We will be using isopropyl alcohol (poisonous to drink) at $3 for a pint, enough for about a thousand cleanings. UK and Benelux readers are recommended to use unflavored vodka, the higher proof the better, as they can take a shot when contemplating the grey skies outside when the process is done. Of course, they will run out of cleaning solution much faster.

You can pay your camera’s manufacturer $$$ to do this task, lose the use of your camera, expose it to the tender mercies of UPS (twice) and still have no guarantee the job will be done right. That’s if you ever get your camera back. You can buy a sensor cleaning kit for some $50 which comes with twelve swabs and magic cleaning solution, which has to be God’s way of telling you you have more money than sense, especially when you use up six of the swabs first time out.

Or you can use Dr. P’s low risk, fast and free method and have the job done in 20 minutes, tops.

You need to concoct a tool which prevents the application of excess force to the sensor glass. No, not that rusty old file from the cardboard box in the basement. Not that the sensor glass protective plate is that fragile, but the cack-handed amongst us can be guaranteed to overdo it. Behold Dr. P’s force-buffered, auto adjusting sensor cleaner.

It’s comprised of two pieces of a regular business card just under 1″ wide (for full frame; make it narrower for APS-C or MFT). The end consists of a multiple-folded piece of lens cleaning tissue, attached at the base to the business card with Scotch tape. Do not use Kleenex – loaded with perfumes and grease and abrasive as heck, it’s a sure way to ensure that you will be sending the camera for service.

First, take a picture of a distant plain object like the sky at the smallest aperture of the widest lens you own. That will bring any sensor dirt into sharp focus.

Next step is to get the swab moist, not wet. Soak a piece of clean, laundered handkerchief in 91% isopropyl alcohol from the drug store, then dab the swab in the handkerchief until you can both see it’s moist and smell the alcohol on it. Do not dunk the swab directly into the alcohol. Moist and wet are diverse concepts. We want moist. Fold up the mirror in your DSLR, remove the lens, insert the swab and swipe across the width of the sensor, flip the swab and repeat. You are pressing hard enough to see the business card bend, not break. If you press too hard the business card will simply break (hence the reference to ‘force buffering!’), limiting the force you can apply.

Wait five seconds for the alcohol to evaporate, down with the mirror, then on with the lens and take another picture. If you need more than five seconds to see the evaporation completed, your swab is too wet. (Readers in England are recommended to use a white wall at home for the picture as it will almost certainly be raining outside).

Now load both snaps into something like Lightroom which will permit before:after comparisons and take a look. If there’s still some dirt there, repeat. There generally is.


You think that sensor glass is fragile? Here’s how Nikon cleans it.

My D3x was simply filthy and needed five or six passes. More crud than crooks in Congress. Better to do these passes one at a time than go into an abrasive frenzy while your swab dries and becomes a fibrous hell. The less you clean, the better. It’s called wear.

To find dirt quickly and to also make it more visible, watch this excellent video.

Here’s the result – Before and After – from identical sections of D3x files, greatly enlarged:

Why does dirt build up on sensors? I discount the oft quoted reason that dirt gets in when lenses are changed, unless you are doing this in dust storms in some hell hole south of the Mason-Dixon during tornado season. I have had dirt build-up even when the lens has not been changed – Canon 5D, Nikon D700, D2x, D3x – makes no difference. It certainly is not squeezing in via the lens mount. The particles are too large. Some lenses – the Canon 24-105 L is one of the worst – act like a dust pump when zoomed, blasting environmental dirt into the mirror box through the zoom mechanism. Don’t believe me – take the lens off, and zoom it holding it to your face. Feel the rush of air? Lousy design, improperly vented.

Other causes seem to be sloppy manufacturing processes. Recent reports of the Nikon D600 show dirt build-up with no lens changes, getting worse and worse during the first five thousand or so exposures. Clearly bits of loose material, and excess lubricants left over from the manufacturing stage are being freed up with use and the typically negatively charged sensor is attracting them in the electrostatic hell between lens and sensor. Witness the fact that D600s lose this problem once well run in and cleaned a few times. Motto: Fire off a few thousand ‘wall shots’ at home before using your new D600. Great. Advice to manufacturers: Stop poncing about with inept ultrasonic vibrators and positively charge the protective glass plate instead.

The Panasonic G1 and G3? Never had a problem in years of use and some 20,000 exposures. The sensors in neither have ever been cleaned and realize that these files are enlarged four times as much as files from a full frame sensor, so dirt really shows. I have changed lenses on these bodies with no special precautions on the street many times. Maybe Canon and Nikon could learn something from the fellows at Panny? And guess what? The Pannys have no flapping mirror doing anything up to 10 gyrations a second and flinging oil and detritus around.

It’s not like Nikon et al are new to screwing up with lubricants. Ask any owner of the 55mm f/2.8 Ai-S Micro-Nikkor, made during a long production run from 1979-2006, if he or she has had problems with gobs of oil appearing on the aperture blades. Yup, wrong choice of type and/or quantity of lubricant.

Here’s Nikon’s pathetic D600 sensor advisory, written by some schmuck liability lawyer who wouldn’t know integrity if it whacked him in the chops and whose job it is to help his employer lie and cheat:


“Natural accumulation of dust”, uh huh. “Blower bulb”, please.
.

Here’s the top secret internal memo from the head of engineering to the C Suite:

“Dudes, we messed up royally. The damned accountants cut so many QC steps from our manufacturing to enhance margins that we had to let our Betty go. She was the babe who mopped up all the excess oil inside our gear before we sold it to pikers. Look, no way we can ‘fess up to this. The liability costs would kill us. We all know these bodies are not really meant to do 8fps but it sure makes for good advertising copy. Let’s just keep a low profile and maybe only one or two come back for cleaning and we can simply say it was operator error. No risk from amateurs and we have the ‘reviewer’ set in our pockets.”


Two beauties against a clean sky.

First and last images – Nikon D3x, 35/1.4 Sigma.

Making huge prints

Tiling is the answer.

Background:

Back in 2005 I wrote about making Really Large Prints. That meant 13″ x 19″, a veritable wallet size compared to what I am doing here. We are talking 36″ x 48″ or seven times the area.

On occasion I have regretted buying the 18″ wide HP DesignJet 90 printer, wishing I had instead paid a little more for the 24″ DJ130. But when it came to making a 36″ x 48″ print the other day, neither could have done the trick. At least not in one pass. And making something really huge for my DJ90’s seventh anniversary seemed the right thing to do.

With my DJ in perfect tune after its annual checkup I was all set, comfortable that perfect colors would result following a recent colorimeter profile session.

Why not just delegate the work?

There are so many variables you cannot control in delegating this task that I discounted the idea in seconds. They include:

  • Finding a good print shop.
  • You have someone making minimum wage, charged out at $100/hr, giving tender loving care to your baby, in between beer and pot breaks. Yes, they will have a jumbo printer which makes this on one sheet. So?
  • Getting the colors matched correctly to your calibrated display image – good luck with that.
  • Getting the big print home undamaged. USPS/UPS/Fedex? Ha, ha, ha! They will fold it to get it into your mailbox. Don’t laugh – that has happened to me before.
  • Longevity. How can you believe the claims made by the print shop for the inks and mounting board? I use original HP Vivera inks which have been tested fade-proof for 80 years by Wilhelm Research. As I’ll be 6 feet under, pushing up the daisies – or maybe fertilizing them – in under half that time, that seems long enough. My mounting board is certified, acid free, Bainbridge Alpha 3/8″ foam core, and will probably outlive King Tut. So there.
  • Satisfaction. Sure, it’s a menial task and one you might not want to do daily. But it is satisfying as it gets doing this yourself and doing it to a higher standard than any agent ever will. I despise the saying “If you want a job done well, do it yourself” because it’s asinine in the extreme, but this task makes for an honorable exception. “Printed by the artist”, don’t you know.

Get my point?

Choosing the right image:

I had a large expanse of wall space viewable from the landing on the upper level but had never quite found a picture to fill it. As I started working on my Golden Gate Bridge series one image immediately suggested itself. Taken from the GGB overlook at the site of the old WW2 battlements, the image is simple, surreal and uncluttered. Just the ticket.


Simple, surreal, uncluttered. The ultrawide 20mm lens used adds to the effect.

Tiling application:

Next it was time to shop around for a good tiling app for the Mac. Tiling apps allows a print to be made over any number of abutting sheets of paper, the result being trimmed and joined just so for display. You can do this in Photoshop but it’s a pain. I settled for the inexpensive SplitPrint which had good reviews and indeed proved capable and easy to use. $5.99.

Preparing the file for tiling:

Before you do anything, examine your file square inch by square inch for sensor spots at 1:1 in your photo processing application, looking especially hard in big, continuous tone areas. Nothing will ruin your day more than finding you have missed some blobs once the print(s) are made. Retouching them now will save a lot of heartbreak later. Just about every sensor will accrue dust and oil spots with use, regardless of whether it has a cockamamie ‘sensor cleaner’ built in or not.

Thereafter the process is simple. I exported the image at the original pixel size of the sensor in the Nikon D3x as a TIF file to Photoshop CS5. Then I ‘uprezzed’ the image to the final print size desired, which would be 36″ x 48″, or four sheets of 18″ x 24″ paper through the printer – the largest it will take. Resolution was set to 240dpi, the maximum the DJ30/90/130 series of printers can handle.

Uprez dialog from Photoshop.

The file was then saved to the Desktop as a JPG, highest quality. SplitPrint at this time only accepts JPG files. No matter. The file was some 45MB in size.

Then into SplitPrint and the required settings were made. I created a custom setting for 18″ x 24″ paper in the Print dialog of SplitPrint and told it to spread the image over four panels thus:


The SplitPrint tile settings.

Dry print runs:

Now 18″ x 24″ paper is not cheap and neither are ink supplies, so I first tested SplitPrint making a 16″ x 20″ print on my office monochrome laser printer using four sheets of 8 1/2″ x 11″ plain paper to see if things aligned and that margins were properly handled. You do not want the margins swallowing any content and neither my laser printer nor the DJ90 can make full bleed borderless enlargements. Margins are unavoidable and the inside ones will have to be trimmed off when assembling the four printed panes.

All went well but, ever cautious, I printed the first panel in color to the DJ90 on a test piece of 13″ x 19″ paper to check that everything was as expected and to verify that colors were true.


SplitPrint printer dialog.

This test confirmed good colors with a perfect match to my display thanks to the EyeOne colorimeter, so I loaded up the printer with four sheets of 18″ x 24″ premium glossy, checked that all the cartridges had ink (running out part way through will not make your day ….) and let her rip, telling SplitPrint to print all 4 images after setting it to use HP Glossy paper with bidirectional printing (‘Best’ quality). This takes a while, some 12 minutes a page, so I did the only rational thing possible. I took my assistant, Bert the Border Terrier, for a walk after the first page started coming out.

Tell me all you want about the romantic days of darkrooms, red lights, blackouts and poison chemicals, for me nothing beats the thrill of seeing a full color image emerging from the DesignJet in broad daylight.


The first pane emerges.

The final prints:

Here’s the finished article, with Bert the Border Terrier for size. I will mount these on acid free board, after trimming the borders (SplitPrint permits small overlaps and draws the cut lines on the images though I had no need of these) then attach all four to the wall, ready for a faux wooden frame. SplitPrint did a perfect job of aligning the images on each page. If it’s of interest I will paint the wooden frame in the colors of the Golden Gate Bridge itself! The paint codes appear below.

Bert and the untrimmed print(s).

Trimming and mounting:

Once the print borders are trimmed (carefully!), the prints are tacked to the mounting boards with the matching sides at the edges of the board. I do not own a 24” trimmer so have to remove the borders with a straight edge and Stanley knife. This is by far the riskiest part of the whole operation, rife with opportunities for error and injury. As the boards are very accurately cut this approach confirms that everything has been trimmed squarely. It’s either right or it looks schlocky. You can opt to leave the margins in place and install these as discrete panels on the wall but I find that sort of thing has been done to death and avoid it:


Tacked prints and boards assembled for dry run to check fit. 26″ bike wheel for reference.

Then it’s off to the dry mounting press to permanently heat mount the prints. Once that is done much of the risk of damage to the fragile prints fades.


In the dry mounting press at 200F. Border Terrier at 102F.

It’s at this point that you start thinking that Michelangelo had it easy daubing that ceiling.

The prints are dry mounted and ready for wall installation:

Ready for hanging.

I use glossy paper. Sure, it’s a pain to work with, fragile as heck and demands very high standards of cleanliness for it shows every blemish, but the result is unrivaled among paper prints for detail, resolution and punch.

Golden Gate bridge paint color codes:

Here are the color codes for those of you into the most beautiful bridge in the world; you can have the shade mixed at your local hardware store to paint any wooden frame you decide to install:


Color codes for the paint used in the Golden Gate Bridge. Click the image for details.

Speed:

There really are no shortcuts here. It’s hard manual labor. SplitPrint makes generating the four panes trivial but after that it’s an exercise in concentration and attention to detail. The next time I do this I doubt I’ll shave more than a few minutes off the total production time, which is several hours. Trimming and wall mounting are by far the most time-consuming steps.

How does it look:

In a word, stunning. While the viewer can get no closer than 10 feet to the print from the second floor landing, even at 2 feet resolution and detail rendering are to die for.

Gear:

Camera? Nikon D3x with the 24mp sensor. But, frankly, a 12mp D700 or any number of similar sensors (FF or APS-C) would be just fine for this setting, though the image would show lower resolution at the same ‘nose in print’ distance. There is more undiluted swill written about the need for high pixel count sensors than you could possibly imagine.

The lens? No magic sauce here either. An old 20mm Ai-S 20mm f/3.5 MF Nikkor – that’s the tiny one which fits in a jeans pocket, handheld at f/8. Mine is 1982 vintage and ran me $215. I added a CPU for $29. You spent how much on that plastic AF-S zoom?


Installed. Wooden frame to come. Prints below are 18″ x 24″.
Cotton gloves on the window sill are used to handle the prints.

Filbert Street

SF’s steepest.

Wikipedia has Filbert Street as one of San Francisco’s steepest and the massive coronary which threatens as you make your way to the top makes it hard to argue.

There’s even a school at the east end, near Coit Tower and what better way to illustrate just how steep it is?


Wikipedia says the steepest section is 17.5 degrees. I borrowed my son’s protractor and checked the bus out. It came to 16 degrees. Close.

The stretch referred to in the Wikipedia piece is here:


Looking east.


Looking west.

You drive down that section in second gear with your foot on the brake …. this section is one way, downhill only.

In the second image you can see Coit Tower at the left (close to the location of the first picture), St. Peter and Paul Church at center-left on Washington Square in the heart of North Beach (Little Italy) and the Oakland Bay Bridge on the horizon. Quite a view. Too bad we don’t bury those power cables.

Nikon D3x, 35mm f/1.4 Sigma (the first) and 50mm f/1.4 pre-Ai Nikkor (the others).