Dr PR

CAUTION: esoteric camera nerd stuff!

 

We sometimes obsess about how many pixels our camera sensors have (mine is bigger than yours ...). But are more pixels ever worse than fewer?

 

I have two principal camera bodies, the Nikon D850 and the Nikon D5600. The D850 camera body sensor has almost twice as many pixels as the D5600 sensor. It would seem the D850 should create higher quality images. But I was curious about the difference in actual image sizes for subjects photographed with the D850 FX camera body and the D5600 DX camera body, using the same Nikon Micro Nikkor 105 mm macro FX lens (a "prime" or non-zoom lens).

 

The full frame (FX) D850 image sensor produces images with 8256x5504 pixels, or 45.44 megapixels. The crop frame (DX) D5600 produces images with 6000x4000 pixels, or 24.00 megapixels. So the D850 images have 1.89 times as many pixels as the D5600 images. This seems like an obvious advantage for the D850, producing images that can be cropped smaller to get the same number of pixels as a similar D5600 image that is cropped much less. But this isn’t the end of the story!

 

 

Full frame (FX) lenses can be used on crop frame (DX) camera bodies. Because the DX sensor is smaller, if used with a FX lens only the center 75% of the image produced by the lens is used (for Nikon cameras - other manufacturers have different full/crop fame ratios). This narrows the view angle, and  increases the effective focal length of the FX lens on the DX camera body by about 1.5.

 

 

 

 

 

This means you can take a picture of an object to fill the DX picture area from about 1.5 times the distance as needed to fill the FX picture area. So from the same distance the image of an object will be much smaller in the FX camera picture than in the DX camera picture (using the same FX lens on both camera bodies). Which camera and lens combination actually gives more pixels for the object being photographed? A simple 1.5:1.0 comparison doesn’t work. The calculations are complicated by the fact that the pixel density on the FX and DX image sensors is different (the D5600 sensor has about 1.2 times as many pixels per mm² as the D850 sensor).

 

To answer this question I took some pictures of a test pattern with the D850 and D5600 camera bodies mounted on a tripod. I used the Nikon Micro Nikkor 105 mm macro FX lens on both camera bodies. On the DX D5600 body the lens is equivalent to a 157 mm lens.

 

 

First I positioned the tripod so the test pattern image filled the D5600/105 mm picture vertically (left). Then I cropped the picture to include only the test pattern image (the outside of the outer black rectangle). The resulting test pattern picture was 5180x3904 pixels, or 20,222,720 pixels (20.22 megapixels).

 

 

 

 

 

 

Then I shot the test pattern with the D850/105 mm setup on the tripod at the same position as for the D5600 shot. As you can see (left), the test pattern image does not fill the picture. After cropping the image to include only the test pattern, the resulting picture was 4632x3496 pixels, or 16,193,472 pixels (16.19 megapixels). This is 0nly 80% (0.800756) as many pixels in the test pattern image as the D5600/105 mm body and lens combination.

 

 

 

 

From the same position, with the same lens on the two different camera bodies, the DX/FX D5600/105 mm setup produced 1.25 times as many pixels for the same object as the FX/FX D850/105 mm combination! So for more distant objects the DX body and FX lens gives greater magnification and more pixels for the objects being photographed.

 

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But what about close-up and macro photography? This is normally of more interest for model photography. For these situations you can position the camera close to the subject and fill the picture area with the subject. How much closer does the D850/105 mm combination need to be to fill the entire picture area with the test pattern?

 

For this test I measured the distance from the initial tripod position where the test pattern filled the D5600/105 mm image picture. The distance from the test pattern to the focal plane was 146 cm (57.5 inches). Then I moved the tripod closer until the test pattern filled the frame on the D850/105 mm setup. The distance was 108 cm (42.5 inches). The DX body/FX lens combination fills the image with the subject at 1.35 times the distance for the FX body/FX lens combination.

 

To fill the picture with the subject the FX/FX body/lens has to be only 0.74 times as far from the subject as the DX/FX combination. The D850/105 mm cropped test pattern had 7344x5499 pixels, or 40,384,656 pixels (40.38 megapixels).

 

At this closer distance the 40.38 megapixel test pattern image in the D850/105 mm has twice (1.99699) as many pixels as the 20.22 megapixel picture on the D5600/105 mm at the longer distance when photographing the same object. So the D850 and 105 mm lens combination is much better for macro photography than the D5600 and 105 mm lens setup.

 

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I normally carry the MUCH lighter D5600 camera body (and FX telephoto lenses) when I am hiking and photographing distant subjects like birds and animals. The D850 is used in the "studio" (my kitchen) when I am doing macro photography of ship models, wildflowers and such. However, on special wildflower expeditions I will carry the D850 and the 105 mm macro lens into the field.

 

Hope this is of interest to someone.

I like the reef points too.

 

I think Wefalck may be right. This boat was on the Yaquina River upstream from the harbor at Newport, Oregon, an old (for the west coast) fishing town. There are a lot of old salts there and I like to think this guy just cobbled up his own rig.

I am curious what this rig is called:

 

 

Looking through Harold Underhill's Sailing Ship Rigs & Rigging (Brown, Son and Ferguson, Glasgow, 1969) it looks like a "cat boat" with an extra shorter mizzen mast (ketch). He shows a "sailing lifeboat" with a similar ketch rig, but it has a fore staysail, the fore sail is loose footed and the mizzen sail is four-sides and has a spar like the fore sail. He also has a drawing of a "sailing canoe" with a similar rig except the mizzen sail is four-sided like the fore sail. A "fishing lugger" has sails similar to the sailing canoe.

Buntlines were rigged in front of the yard.

 

The lines attached to the bolt rope at the foot of the sail. From there they ran up the front of the sail to blocks or thimbles attached to the front of the yard. After passing through the block/thimble the line passed over the yard to another block fastened under the top, above and behind the yard. From there the line ran down to the deck.

 

There were several variations with different types and numbers of blocks. But I think in all cases the buntlines ran up the forward side of the sail and yard.

Propellers are intended to push a vessel through the water. The faster a propeller rotates, the greater the push. Increasing the size (diameter) and area of the propeller blades produces more push for a given RPM. The larger the diameter the faster the end of the propeller blade rotates at a given RPM. If the end of the propeller blade moves too fast it moves faster than water can move. As it turns it leaves holes or vacuum bubbles in the water. This is called "cavitation" and it causes two problems.

 

First, there is a lot of energy involved and cavitation can rip bits off the trailing edge of the propeller - and even cause pits in the blade surface. This will create imbalance in the propeller, and that creates vibrations in the prop shaft that can wreck the foundations in the shaft alley and even destroy the turbine or motor turning the shaft. This is considered a bad thing.

 

The second problem is noise. When the cavitation vacuum bubbles collapse they create a popping noise. This is like going into the reading room of a library and banging on a pan with a hammer. Everyone within hundreds of miles can hear cavitation. It is anti stealth!

 

So if you can't have one big propeller turning really fast to get the push you need, the solution is multiple smaller propellers turning slower than the speed that causes cavitation. And modern "twisted blade" propeller designs were created to minimize cavitation.

 

 

On larger ships the loading tackle (burton tackle) ran down from the topmast head (assuming there was a topgallant mast). On smaller vessels without burton tackle came down from the lower masthead.

Beautiful schooner, with a classic sail plan. It will make a great model!

Sascha,

 

You have created a beautiful model! And it is even more impressive knowing you used simple tools, and you have great skill working with them.

It is a beautiful ship, and the model deserves to be finished!

 

How large is this model? What scale? From the photo looking down at the decks it is clear from the chair beside the model that it is pretty large!

 

The ship had a lot of sails (the first photo). The square sails appear to be typical late 19th and early 20th century clipper rigs, but the mizzen mast is different. I knew that some vessels  used a two-part driver on the mizzen, but I think this is the first picture I have seen.

 

I am not sure what the  upper "driver" sail is called. Underhill (Masting and Rigging the Clipper Ship and Ocean Carrier, page236) describes a "unusual rig" on the barquentine Transit that had three fore-and-aft sails on all but the fore mast. Underhill says these were called the "course," "topsail" and "topgallant." These were gaff sails and not square sails. The lower were two four-sided gaff sails, and the top triangular sail a more or less normal gaff topsail.

 

I haven't see these terms used for fore-and-aft sails anywhere else. But the Transit was unusual in almost every way, so unusual terminology can be expected!

Planking the deck is simpler than you might think. The question is whether it will nag at you if you don't try to make it "authentic" (whatever that means).

 

We learn from every build we do. If you plank the deck on this build, the next time it will be "old hat.""

 

Here is a link to the deck planking I did on my current model:

 

https://modelshipworld.com/topic/19611-albatros-by-dr-pr-mantua-scale-148-revenue-cutter-kitbash-about-1815/?do=findComment&comment=605072

 

I have a question for you all.

 

I first load all of the images I want to use. They are already formatted to "thumbnail" size (about 1000 pixels wide). Then I put the cursor where I want a picture in the text and click on the image I want in the images below.

 

So far this is what everybody else has said.

 

Then I double click the image and resize it to about 900 pixels, or 400 pixels wide for placing two pictures side by side. These will fit easily on a small size screen. However, if you click on the image you can see them full size.

 

Sometimes I place the first image left justified, and a second image beside it with no justification. Or maybe I put a tall image on the left and two shorter images beside it on the right, or maybe another small image and some text.

 

This looks OK on my screen, but I have no idea if others can see these side-by-side images. Does it come out OK on your screen?

 

Here is a link to an example post with photos and text mixed in several ways.

 

https://modelshipworld.com/topic/19611-albatros-by-dr-pr-mantua-scale-148-revenue-cutter-kitbash-about-1815/?do=findComment&comment=1029254

 

The futtock shrouds transfer forces from the topmast shrouds to the mast. Therrefore, I would think they would be the same diameter as the topmast shrouds. Lees' Masting and Rigging of English Ships of War says the futtock shrouds were the same size as the topmast shrouds.

Nils,

 

That is a clever idea! The letters do look good!

There is another way to create lettering.

 

1. Paint the surface area around the lettering with the color of the letters.

 

2. Use rub-on letters as stencils, positioning them where you want the letters.

 

3. Paint over the letters and surrounding area with the background color.

 

4. Remove the rub-on letters.

 

This produces lettering only as thick as the paint, and it will not age, become discolored and peel off with time. You can make any color letters from any size and font rub-on letters you can find. And the lettering paint will conform to any surface features.

We had one of these in the shop at work - back in the corner collecting dust while all the work was done on a larger lathe. It came from one of the fellow's dad who bought it back in the 30s or 40s. I disassembled it and cleaned it. Then I put it back together and aligned it and it worked really nicely. Very solid!

 

Yours should last forever.

Glue isn't needed. After all the rigging is installed the masts and bowsprit aren't going anywhere!

 

I prefer to install the cradles for the bases of the mast on the keel/keelson and frames for just below the deck planking while the hull is open to work on. I get everything aligned so the masts are aligned and raked correctly. Then when the masts are finally inserted into the hull they will be aligned correctly.

 

The same is true for the bowsprit. It should have a heel and tenon that fits tightly between the bitts/knightheads, timberheads (whatever you want to call them). This should prevent the bowsprit from slipping backwards between the posts, and it should hold the bowsprit in alignment. If the bowsprit can slip between the posts drill a hole down through the assembly and install a pin to hold it in place.

Bob,

 

Thanks for the information on the pig stick!

It is interesting that this topic came up now. Yesterday I watched a video of the ketch Bessie Ellen sailing the Hebrides Islands recently.

 

Tall Ship Sailing the Hebrides:

 

https://www.youtube.com/watch?v=mElJHueAUmM

 

When they neared port a pennant with the vessel's name was flown from the main truck. So the tradition is still used in England (the vessel was registered in Plymouth).

 

If I remember correctly (it was just a brief bit of the video showing them raising the pennant) the pennant was on a short spar. It appeared one end of the halyard was attached at about the middle of the spar, below the pennant. It lead up to the truck and back down (like a flag halliard), where the other end was attached to the bottom of the spar. As it was hoisted some drag was applied to the line on the lower end to hold the spar upright. When it reached the top both ends were belayed together at a pin rail.

 

The pennant was triangular, and I think it was white with a red border and red lettering. There are lots of images of the ship with the pennant flying right at the beginning of the video, especially at time 3:55.

John,

 

Nice work on the sails, and nice attention to details.

 

Isn't it interesting how a simple triangular sail with just a halliard, two sheets and a tack can turn into a plethora of blocks, hooks, lines fairleads, pins and cleats - not to mention the hanks. Oh yes - the downhauls with even more of the same!

Aha! Better late than never!

 

I wonder of the topsail rig shown on the Jolie Brise is a sliding gunter rig? See posts #84 and #85.

 

In this topsail rig the sail peak, and often the upper part of the forward edge (luff), is attached to the vertical yard. The lower part of the luff hangs free. The yard slides in rings near the top of the mast. A halliard hoists the spar to it's upper position, taking the sail up with it. A line on the sail tack pulls the sail down taut. To lower the sail the spar is lowered so it no longer catches the wind. It is a popular rig on smaller vessels.

 

The clew is attached to the end of the gaff and the tack is pulled down by the tack line.

Coiling lines on deck is a popular modelling technique, especially for gun tackle rigging. It is "pretty" but would never happen on a ship at sea. The lines would soon scatter into a tangled mess on a rolling deck. Lines would be coiled only in port, and then only when the ship was undergoing inspection or open to the public for special visiting days. At other times the decks would be cleared and the gun tackle might even be stowed below.

 

How are you planning your model? Is it rigged for action at sea or just idle and tied to the pier?

You were talking about making sails and looking for a material of approximate scale thickness. I am currently working on sails for my 1:48 schooner and I am using the thinnest #00 silkspan. It is 0.0015 inch (0.0381 mm) thick. Here are some scale thicknesses for comparison.

 

Scale          thickness

               inch         mm

1:1          0.0015     0.0381

1:24       0.036       0.9142

1:48       0.072       0.3048

1:64       0.096      2.4384

1:72       0.108       2.7432

1:96       0.144       3.6576

1:200     0.300      7.6200

1:350     0.525    13.335

 

So silkspan is a reasonable scale material for sails at scales from 1:40 to 1:96. It may be a bit too thin for 1:24, and too thick for 1:200.

 

Another thing you might try is parchment paper (used for cooking). It is only 0.0005 inch (0.0127 mm) thick. The resulting scale thicknesses are 1/3 of what is shown for silkspan. It might work for scales down to 1:200. However, it is fairly stiff and might resist any complex shaping - especially for furled sails.

Copper plating was introduced in the last half of the 1700s. But it was expensive and not used on many smaller vessels. A common anti-fouling surface was a mixture of turpentine, white lead and tallow. This is the "white" bottom you see on many vessels of the 1700s and 1800s.

Like everyone else I have no idea what he is talking about. "Z" dimension? Is that vertical, longitudinal or transverse? Short in height? Lower in the middle?? Is the propeller amidships?

Bruma,

 

There was no hard fast rule where any particular line free end (running end) was belayed. But there are some general suggestions for all lines.

 

1. If a line descends from a position near the mast it should belay close to the bottom of the mast (fife rail, pin collar, cleats, etc.).

 

2. If a line originates from a position near the end of a yard (yard arm) it should belay to a point on or near the bulwark (pin rail, cleat, etc.).

 

3. Lines coming from positions lower down in the rigging belay to positions forward on fife rails, pin rails, etc.

 

4. Lines from positions higher up in the rigging belay to points farther aft.

 

Of course, rules are made to be broken and it was common on ships with lots of sails (like clippers) for some lines originating higher up near the masts (for topgallants and royals) to be lead outboard through thimbles on the shrouds and then down to pinrails at the bulwarks.

 

5. There was one rule that must never be violated - all lines will be routed so they don't tangle with other lines or parts of the rigging.

 

One other thing - sometimes two lines were belayed to the same pin. For example, when a sail is fully set flying the bunt lines and clue lines are slack with no strain. They are both used at the same time when the sail is being pulled up for furling. Then when the sail is furled to the yard they are slack again. So these lines can be belayed on a single pin (port and starboard).

 

I wish I could be more specific for the Cutty Sark (I am pretty sure I built a plastic model of that ship when I was a kid). This is all complicated enough on a small vessel like the topsail schooner I am modelling. You are working on a ship with more sails than the laundry at a hospital on wash day! There are many more lines, and therefore, more opportunities for fouling the lines. Study the ways Campbell and Underhill routed the lines and do your best to rig your model in a similar way. When you are finished, if everything runs free without fouling you will have done it right!