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A evaluation of focus magnification aids, together with two Bahtinov (masks) filter merchandise to realize exact infinity focus for astrophotography or nightscapes.
Acquiring a pointy infinity focus is the keystone to good astro-landscape pictures. In case your stars are usually not in focus, your shot is ruined, irrespective of how lovely and nicely deliberate! I can not let you know what number of occasions in my early nightscape adventures that I’ve come again from an incredible evening pictures shoot solely to be dissatisfied once I enlarged my photographs on the pc display—discovering that the celebrities have been barely out of focus, and that I would by no means be capable of make an honest measurement print out of my efforts.
What do out-of-focus stars look gentle? These two lovely photographs have been taken final month by R. Craig Lefebvre in Arches Nationwide Park (left) and Lifeless Horse Level (proper), Utah. As a result of the Arches picture was taken with a 15mm lens, the 4 stars proven under Jupiter, within the Sagittarius constellation, needs to be about 40% smaller than the identical stars shot with the 24mm lens, but they’re really bigger. And, the rationale they’re larger is as a result of they’re barely out of focus. Sadly, it’s virtually unattainable to see this drawback till the pictures are projected to 100% on a pc monitor—or through the use of a number of the superior methods under. Observe: This picture is just very barely out of focus. It nonetheless can be utilized for social media and probably for prints as much as 16×20 inches. Out of focus stars which are twice this huge (even blurrier “circles of confusion“) are sometimes not detected till it’s too late. In these circumstances, the picture is nugatory for any sensible use.
Begin with You Digital camera’s Reside View: Miss-focus nonetheless occurs to me often, and I proceed to see and listen to about this disappointment and frustration from my fellow nightscapers, particularly those that are simply beginning out. On web page 53 of my Milky Means NightScapes eBook I exploit three paragraphs on how you can manually focus and discover your true infinity with the digicam’s Reside View perform. I then finish with, “When you’ve discovered your lens’ true infinity, mark it for future reference, or tape down the main focus with a chunk of gaffer’s tape. You’ll have one much less factor to fret about at the hours of darkness.”
Temperature Impacts Focus: That recommendation works more often than not, however I’ve discovered that you may’t at all times depend on it as a result of the tape can loosen or the main focus mark grow to be meaningless due temperature adjustments. Adjustments in temperature could cause appreciable focus shifts in your lens, so it’s best to redo your focus every time you exit capturing at evening. And, if temperatures are significantly completely different than the final time you have been capturing, wait a number of minutes in your lens to regulate to the brand new outdoors temperature.
Zoom lenses usually have a special infinity focus for every focal size, so no single infinity focus setting provides you with correct outcomes all through the zoom vary of the lens.
Further magnification to your Reside View picture: As we become old, it turns into a lot more durable to see if a star is sharply centered on a 3-inch LCD digicam monitor, even when the picture has been magnified to 10X. For that reason, I carry an affordable pair of +3.0 diopter (energy) studying glasses from my native drug retailer. This, or a Hoodman Loupe (with the Hoodman Cinema Strap) permits for hands-free, enlarged views of your little digicam monitor.
Aaron King of Photog Adventures continues to advertise his favourite focusing help: The $5 Carson Lumiloupe 10X magnifier (proven within the above center picture). This is his 13-minute video tutorial. I’ve used this technique for years, and I extremely suggest it!
The Bahtinov masks focusing help:
The Bahtinov masks is a tool used to precisely focus small astronomical telescopes. This distinctive sample was invented by Russian beginner astrophotographer, Pavel Bahtinov, in 2005. The telescope is pointed at a vibrant star, and a masks is positioned in entrance of the telescope’s goal. The masks’s three separate grids are positioned in such a means that they produce three angled diffraction spikes on the focal aircraft. Because the telescope focus is modified, the central spike seems to maneuver from one aspect of the star to the opposite. Optimum focus is achieved when the center spike is centered between the opposite two spikes. In the event you like DIY tasks, you possibly can even make your individual Bahtinov masks.Bahtinov masks limitations and new product options: The issue with most Bahtinov masks is that they work nicely for small telescopes and medium to lengthy telephoto lenses on cameras, however their use with large angle lenses which are usually utilized in astro-landscape pictures will not be as decisive.
Enhancements on the Bahtinov masks design: These two commercially accessible Bahtinov masks “filters” try to offer a extra correct and easier-to-use focusing instrument for nightscape photographers. In contrast to the standard Bahtinov grid or masks, these are extra like true photographic filters. Within the case of the SharpStar2 filter, the Bahtinov masks sample is finely etched by laser into the clear plastic filter. The Give attention to Stars filter goes even additional with a number of Bahtinov masks patterns contained in a movie that’s sandwiched between tempered glass sheets.
Is a star focusing filter actually obligatory? Some might imagine there isn’t a want for devices like this to help photographers in getting a pointy give attention to their stars, contemplating the accessible focusing instruments I’ve already talked about. I admit, that I used to be certainly one of these individuals (I do not want extra stuff cluttering my digicam bag). Nonetheless, as I’ve helped a whole lot of scholars in my nightscape workshops over time and seen them wrestle to get an accurate give attention to the celebrities, even with these different instruments, I am starting to suppose there’s a want for a greater focusing instrument, and one or each filters of those could be it—particularly as we become old and we wrestle studying the small print (the celebrities in your LCD display are even smaller, even at 10X!
Contemplate this: {Many professional} photographers resisted auto focus when it first appeared on professional SLR cameras again within the 80’s—now, few of us would consider being with out it! When articulating LCD digicam screens first appeared a couple of years in the past on low-end digital cameras, many scoffed at these as this gimmick. Now, they’re quick changing into a “obligatory”‘ function in skilled cameras.
PRODUCT PREVIEWS…
SharpStar is a straightforward instrument created by Lonely Speck to assist astrophotographers obtain essential give attention to the celebrities with their digicam lens and filter holder. SharpStar claims to assist astrophotographers obtain good give attention to the celebrities, each time.
Lonely Speck’s SharpStar2 is manufactured from precision laser etched optical plastic and is available in a sq. filter form, made to suit into the most well-liked sq. filter methods. SharpStar2 requires a sq. filter holder and the appropriately-sized system adapter ring to suit your lens (each objects offered individually). The SharpStar2 works with the Lee, Cokin, Formatt-Hitech and different comparable filter holders that are available in 85mm, 100mm and 150mm sizes. In the event you don’t have already got a filter system, Lonely Speck personally recommends the Formatt Hitech system due to its worth and its modular design that works nicely with large angle lenses. October 9 replace from Lonely Speck: “The SharpStar2 is made within the USA. We provide a 100% satisfaction assure (refund or alternative if the shopper is not happy for any purpose). All they should do is e-mail us.” ~ Ian and Diana
PRICING (filter solely – filter holder not included):
- 85mm $64.00
- 100mm $69.00
- 150mm $94.00
Filter Pouches are elective (soft-lined semi-rigid pouch with magnetic closure)
 ~ 85mm $12.00 • 100mm $14.00 • 150mm $20.00 ~
The Focus On Stars excessive precision gadget suits into normal measurement sq. filter holders accessible available on the market. At first look, it appears to be like like a filter.
In actual fact, it has a grid construction based mostly on the Bahtinov masks identified in astronomy, however it’s rather more complicated. A mess of Bahtinov masks in a particular mosaic structure ensures that every one three diffraction spikes are obtained rapidly and simply with a most of two small actions (horizontal rotation, vertical slide). You solely want to position it in entrance of the lens to fine-tune the main focus, and you may take away it earlier than the ultimate publicity. In accordance with the principles of diffraction, 3 pairs of vibrant spots seem on the LCD dwell picture across the brighter stars.
Focus On Stars developer, Gabor Takacs, claims that his filter works higher with the large angle lenses mostly utilized in astro panorama pictures: “Throughout my analysis, I discovered a promising gadget that the producer really helpful additionally for lenses with shorter focal size. It’s a plastic sheet wherein the grid strains of the Bahtinov masks identified from astronomy have been densely etched with laser. I’ve examined it. Utilizing wide-angle lenses widespread in astro panorama pictures, I’ve discovered that this gadget offers me a diffraction sample that’s too faint and too small to make sure a pointy focus. …After greater than a yr of analysis and improvement, I develop a tool that works nicely even with ultra-wide-angle lenses.”
The Focus On Stars diffraction sample has some similarities to the standard Bahtinov masks, however can also be has some distinctive variations that assist the person decide focus with extra precision. When focusing, the middle spot across the focused star strikes between the lateral spots. When the middle spot is simply equidistant from the lateral ones, i.e., the ensuing sample is symmetrical, the main focus adjustment is ideal. The place of the intermediate spots additionally reveals the path of the required correction: If the spot is shifted to the left, the main focus is in entrance of the goal, whether it is shifted to the precise, it’s behind the goal. October 12 replace: “Focus On Stars is made in Hungary (EU) and we additionally supply a 100% satisfaction assure (refund or alternative if the shopper will not be happy for any purpose).” ~Â Gabor Takacs.
PRICING (filter solely – filter holder not included):
- 100mm $113.00
- 150mm $154.00
Every filter comes with a protecting, hand-sewn pouch with velcro closure :
My OUT OF THE BOX Expertise
SharpStar2
I ordered the 100mm SharpStar2 for $69.00, with economic system delivery from California (U.S.A.) to Utah (U.S.A.) for a value of $3. I acquired a notification the subsequent day that the product was out of inventory. Two days later, the product was accessible and I acquired one other notification that it was delivery. The bundle arrived three days later, and included a filter pouch (a $14 worth) that I did not order. Once I questioned (by way of e-mail) the inclusion of the pouch I did not order, they stated it was free as a result of my order had been delayed because of stocking issues (good gesture!). Whole value for filter with delivery to the united statesA. was $72. Nonetheless, if I lived in Australia, my USPS Precedence Mail Categorical Worldwide delivery value could be $82.75, for a complete value of $151.75.
All-in-all, the merchandise have been simply as described, and properly packaged. The filter was enclosed in a transparent plastic envelope (blue product description printed on the surface), which might be used a storage pouch for some time, however the true filter pouch (manufactured from suede leatherette materials), with its magnetic enclosure, was a lot nicer and extra substantial. The filter appears to be finely etched with the Bahtinov masks sample right into a sheet of clear plastic.
Focus On Stars
I ordered the 100mm Focus On Stars for $113.00, with DHL Categorical delivery from Hungary to Utah (U.S.A.) for a value of $32. The FOS filter comes with its personal padded pouch. I acquired a notification the subsequent day that the product was delivery. The bundle arrived 4 days later. Whole value for filter with pouch and delivery to the united statesA. was $145 — about twice as a lot because the SharpStar2 (nonetheless, you do get a pouch embody). I observed that top worldwide delivery value outdoors of america for the SharpStar2 have a tendency to boost its whole prices nearer to that of the FOS filter. For example, if I lived in Australia, my DHL Categorical delivery value for the FOS filter could be $42, for a complete value of $155 (making it solely about $2 extra in whole value than the SharpStar2).
All-in-all, the FOS filter and pouch have been simply as described, and properly packaged. In contrast to the SharpStar2, the Focus On Stars filter is manufactured from tempered Gorilla 3 Glass, not plastic, and claims to be very scratch resistant. It was additionally a lot simpler to wash off my fingerprints and dirt, because of a particular coating that’s utilized to the glass.
150mm variations of SharpStar2 and Focus On Stars
I used to be additionally in a position to acquire the bigger 150mm variations of those two filters, which I’ve held on a garments line for a visible comparability so you possibly can rapidly see the density variations of those two filters. Due to its complicated mosaic sample, the FOS filter is about one to 2 stops darker than the SharpStar2 (about 0.3 to 0.6 optical density). Will this additional density hinder in your skill to see its star focusing sample at evening, when in comparison with the extra clear SharpStar2 filter? It did not appear to be an issue in my subject exams (see under).
Precise Area Exams
Preparation
Until you have already got a Cokin P or Formatt-Hitech filter holder system for 85mm sq. filters, I’d keep away from this technique measurement, because it has limitations for the extra severe beginner or skilled photographer; and the Focus On Stars filter can also be not accessible on this measurement.
Focusing Procedures with the Filters
The next steps have been used within the subject with each the SharpStar2 and Focus On Stars filters:
- Turned off the autofocus and rotated the lens focusing ring to the infinity mark.
- With the digicam on a tripod, pointed it on the brightest star within the sky, in order that it was within the middle of the digicam’s subject of view. The brightest “star” was usually the planet Jupiter.
- Activate the digicam’s “dwell view” picture and amplify the star to the utmost.
- Insert the focusing filter into the filter holder.
- Manually modify the main focus to trigger the center diffraction spike or diffraction spots (within the case of the Give attention to Stars filter) to middle between the outer spikes or spots. The symmetry of the sample ensures good focus.
- Take a “affirmation” take a look at shot and evaluation the picture underneath magnification.
- Make focus changes till good sample symmetry is achieved.
- When the middle spikes or spots are evenly centered, take away the focusing filter and level the digicam optics on the scene you wish to seize.
These steps labored advantageous with my 70mm, 50mm, 35mm and 24mm lenses; nonetheless, with the 15mm and 14mm extremely wide-angle lenses, even the brightest stars have been so small, I needed to take these further steps to get the perfect sample symmetry:
- I usually needed to rotate the digicam a couple of levels horizontally on the tripod head till I noticed at the least two pair of spikes or two rows of dots.
- I then needed to arbitrarily slide the focusing filter, within the holder, up and down till all three pairs of spikes or spots turned seen.
Utilizing these further steps, with the 14mm and 15mm lenses, gave me lovely diffraction sample symmetry and excellent focus with the Focus On Stars filter. Seeing and attaining an excellent diffraction symmetry sample with the SharpStar2 filter was rather more tough when utilizing extremely wide-angle lenses, as you may see within the following photographs.
Area Check Comparisons
Each the SharpStar2 and the Focus On Stars filters produced glorious symmetrical diffraction focusing patterns when utilizing a 70mm lens (a 24-70mm zoom @ 70mm). They each produced good patterns utilizing a 50mm lens (a Samyang/Rokinon 50mm f/1.4). The colourful Focus On Stars sample is extra distinct to my eyes, and simpler to guage when it has reached symmetry (good focus). Nonetheless, each merchandise carried out nicely within the 35mm via 70mm vary.
Utilizing a 24mm lens (Samyang/Rokinon 24mm f/1.4), symmetry was a lot simpler to see with the Give attention to Stars filter than the SharpStar2; nonetheless, the SharpStar2 was acceptable so long as you used a really vibrant star, i.e. the planet Jupiter, and also you used a loupe that will help you amplify the digicam’s LCD display.
The Focus On Stars simply out carried out the SharpStar2 when utilizing an extremely wide-angle 14mm lens (Samyang/Rokinon 14mm f/2.8). Even with a 10-power loupe to amplify the again of the digicam’s LCD display (already magnified to 10X), it was tough to see when there was spike sample symmetry utilizing the SharpStar2. A number of picture confirmations and slight focus changes needed to be made with a purpose to get the perfect sample. I had just about the identical irritating outcomes utilizing a 15mm extremely wide-angle lens (Irix 15mm f/2.5).
You will discover that with the identical affirmation publicity, the Focus On Stars picture is a couple of cease darker than the SharpStar2 picture. As I discussed earlier, the Focus On Stars filter is darker because of its complicated mosaic sample. I did not discover that this additional density hindered with the ability to see or acquire an excellent symmetrical focusing sample. In addition to, the filter is eliminated earlier than beginning your inventive astro pictures.
A Work-Round Technique to Enhance Your Outcomes
My process was to position the Lume Dice gentle about 100 paces from the digicam (and intention the sunshine again in the direction of the digicam). You may place the sunshine on a rock or use a light-weight stand. This creates a distance of at the least 200 toes (61 meters) from the lens—greater than sufficient for any large angle lenses to optically be at an “infinity” distance. I exploit a diffuser filter over the sunshine, in order that it’s not a centered gentle, and I scale back its depth right down to about 10% (go increased, when you nonetheless have hassle getting an excellent focusing sample).
As a result of this synthetic, man-made “star” is such the next “magnitude” than actual stars, your publicity will solely must be a couple of seconds, utilizing a low ISO of about 200. This publicity will sometimes offer you better distinction (a darker background) than actual stars within the sky, which also needs to produce a bigger and crisper focusing sample, even with the Focus On Stars filter—albeit this additional effort is one thing I discover isn’t wanted with the FOS filter.
My Conclusions
It might appear ridiculous to spend a median of $108 for a focusing help (and much more when you do not have already got a sq. filter holder system), however lacking one nice Milky Means shot because of inaccurate focus will treatment you of this opinion, particularly when you think about the journey prices you spent to get to a terrific location.
SharpStar2
PROS: Inexpensive than the Focus On Stars filter. A very good focusing help for all lenses up via as large as 24mm (or 16mm when utilizing an APS-C cropped sensor).
CONS: It’s tough to realize good outcomes with extremely wide-angle lenses i.e. the 14mm and 15mm lenses (I think that 20mm and 18mm lens customers can even have some difficulties). Plastic development makes the filter extra vulnerable to scratches, and is more durable to maintain clear. A protecting filter pouch will value you an extra $12 to $20.
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Focus On Stars
PROS: It’s simple to acquire a decisive symmetrical focusing sample with this focusing filter (apparently because of its extra complicated mosaic masks), particularly with extremely wide-angle lenses within the 14-16mm vary. Development high quality is great. The filter sample is sandwiched and sealed between tempered Gorilla 3 glass, making it simpler to withstand scratches and to wash. A protecting filter pouch is included.
CONS: Costlier than the SharpStar2 filter (U.S.A. purchasers will spend virtually twice as a lot for the FOS, with delivery prices, than consumers of the SS2); nonetheless, pricing turns into nearer for a lot of worldwide purchasers because of inexpensive delivery prices (Australian FOS purchasers can pay virtually the identical whole worth as SS2 purchasers and European FOS consumers will really spend much less). The inclusion of filter pouch additionally helps to even out the worth distinction.
Disclosure: I’m NOT receiving any earnings from the gross sales of the SharpStar2 or Focus On Stars filters. The hyperlinks to the LEE filter holder methods are being monetized via B&H. Apart from that, this weblog submit is only for academic functions.
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