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Messages - IMG_0001

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1
Lighting / Re: Flash Zoom - Difference in Stops?
« on: July 29, 2014, 03:53:20 PM »
2^F = (GN2/GN1)^2

Then from 24mm to 70mm, F=1.67 stops (+1 2/3)
70mm to 200mm,  F=0.52 stop (+1/2)
So of course 24mm to 200mm, F=2.19 stops.

OK, so you're taking the log base 2 of both sides of that formula to solve for F.
But can you tell me where that formula comes from?  All I know is the GN = f * d formula and the Inverse Square Law formula (Intensity = 1 / distance^2).  Would like to know how you derived it.

First, to clear things off, I advise to just stick to the basic GN = F*d which gives the right results and is much more tractable on the field.

As for my formula, I just went on from basic physics.

Intensity I is Power over Area --> P/A

A, the area lit, increases to the square of the distance from the source -->A proportional to d^2

Therefore, I is proportional to P/d^2 (not equal to)

Then, given that power remains the same --> P1 = P2 entails that I1*d1^2 = I2*d2^2 or, I1/I2 = (d2/d1)^2

Now, that is for the flash in a fixed zoom setting.

Now considering that the subject distance is fixed and posing that Case1 is for 24mm and GN28m and Case2 is for 70mm and GN50m. Zooming from 24mm to 70mm is like moving the subject from a distance of 50m to a distance of 28m. Then d2/d1 = GN2/GN1 and :

I1/I2 = (GN2/GN1)^2

Finally, in photography the aperture F goes up one stop every time the light intensity doubles so I is proportional to 2^F. It ensues that:

2^F = (GN2/GN1)^2

I hope this helps.

2
EOS Bodies / Re: Is there something wrong with my 5D Mark III?
« on: July 28, 2014, 03:39:27 PM »
Granted the white balance is off, but otherwise you are stupefied that a camera with 50% more pixels on the same sensor size and mounted to a lens that frame the subject 50% tighter gives you more details? Now I'm stupefied...

3
Yes it did, here is mine.


It looks Novoflex still produces something alike, although less sophisticated (there's no bellows between the lens and the film): http://www.novoflex.com/en/products/macro-accessories/focusing-racks/castel-cop-digi/

Anybody knows why Canon never made for the EOS those macro accessories once available, and switched to a very specialized lens only like the MP-E 65mm? It's an excellent lens, but I find it less versatile than a bellows (especially since it comes without a focusing rail). Anybody tried the Novoflex bellows?


I have an old Novoflex macro bellows and Novoflex noflexar 105mm f4 bellows lens. I've bought it about 2 years ago and use it now and then.  In its early life, it was used in a medical context. It is alright in terms of sharpness but has some CA. Lightroom does a good job of getting rid of those though. The rail mechanism is a bit rough on my copy, but I think I could give it a cleanup and it would be smooth. Having an integrated focus rail, even a stiff one, is great nevertheless.

I don't have a slide copy attachment so I can't comment on that.


4
Macro / Re: Mechanicals
« on: July 27, 2014, 02:45:50 PM »
Intersting story, I'll check the link for sure. That Sheldon Brown site is a bible for cyclist isn't it. Personally I've been riding a fixed gearfor a few years as I mainly ride around the city and park in crowded bike racks where I've had my derailers bent a few time. Fixies are so much more reliable and give so much feedback when riden with cleats.

I've built a commuter bike based on a single speed mountainbike frame that addresses that by using an 8-speed internally geared hub. The first photo shows the hub when the bike was new (april 2004). At that time the bike looked like a proper mountainbike with nobby tires and without fenders. The photo was taken with my first digital camera - a Canon PowerShot A20.

The second photo shows the current state of affairs after 10 yrs, the bike has evolved into even more of a city bike with fenders, narrow slick tires and such. Still with the same hub though which now has more than 15000 km on the clock. This photo was taken with a Canon Powershot S90 that I now use for such 'practical' pictures.

I've spent several months in NL in 2011 and it is flat indeed, although the wind can be quite strong along the Ijsselmeer. Needless to say that my Canadian home town now feels so unfriendly to bikers since I've been in NL though.

Yes sometimes I say the wind is our hills. Sometimes the wind feels like a mountain too  :-\ NL is a very bicycle minded country, but for mountain biking and the spectacular nature I think I'd prefer to be in Canada ;)

That looks like a nice bike to ride around on. A friend of mine rides a 3-speeds Nexus hub and also has the front generator/brake hub on a vintage bike. He actually had his front fork breaking off at the shoulder as it was designed for a rim brake and the hub brake force had too much leverage. Luckily, it broke down when he was almost stopped so only minor bruises. I guess this front hub is better for replacing disks.

Here in Montreal, bike theft is such a plague that I'd rather have as inexpensive components as I can. Those Nexus are too expensive for my taste and I've been too frustrated having my stuff stolen. On the other hand, a fixie built on an old road bike fits the bill perfectly.

On theft, I think here in the Netherlands, bicycles are almost considered public property so I make sure to use a good lock. If I think it's iffy I'll use an old crappy bike.

My two locks are the most expensive parts on my bike apart from the wheels. The thing is that you can't really lock your hubs and you can just unbolt them and rip the spokes off. Thief will go there here. It is amazing because Montreal is such a safe place otherwise.

5
Macro / Re: Mechanicals
« on: July 27, 2014, 01:11:35 PM »
Thanks for the inspiration all.  I now need to go and find those Prost F1 gears and spark plug I have stored :D

I'll be very angry at you if you don't!

6
Macro / Re: Mechanicals
« on: July 27, 2014, 01:09:31 PM »
Intersting story, I'll check the link for sure. That Sheldon Brown site is a bible for cyclist isn't it. Personally I've been riding a fixed gearfor a few years as I mainly ride around the city and park in crowded bike racks where I've had my derailers bent a few time. Fixies are so much more reliable and give so much feedback when riden with cleats.

I've built a commuter bike based on a single speed mountainbike frame that addresses that by using an 8-speed internally geared hub. The first photo shows the hub when the bike was new (april 2004). At that time the bike looked like a proper mountainbike with nobby tires and without fenders. The photo was taken with my first digital camera - a Canon PowerShot A20.

The second photo shows the current state of affairs after 10 yrs, the bike has evolved into even more of a city bike with fenders, narrow slick tires and such. Still with the same hub though which now has more than 15000 km on the clock. This photo was taken with a Canon Powershot S90 that I now use for such 'practical' pictures.

I've spent several months in NL in 2011 and it is flat indeed, although the wind can be quite strong along the Ijsselmeer. Needless to say that my Canadian home town now feels so unfriendly to bikers since I've been in NL though.

Yes sometimes I say the wind is our hills. Sometimes the wind feels like a mountain too  :-\ NL is a very bicycle minded country, but for mountain biking and the spectacular nature I think I'd prefer to be in Canada ;)

That looks like a nice bike to ride around on. A friend of mine rides a 3-speeds Nexus hub and also has the front generator/brake hub on a vintage bike. He actually had his front fork breaking off at the shoulder as it was designed for a rim brake and the hub brake force had too much leverage. Luckily, it broke down when he was almost stopped so only minor bruises. I guess this front hub is better for replacing disks.

Here in Montreal, bike theft is such a plague that I'd rather have as inexpensive components as I can. Those Nexus are too expensive for my taste and I've been too frustrated having my stuff stolen. On the other hand, a fixie built on an old road bike fits the bill perfectly.

7
Macro / Re: Mechanicals
« on: July 26, 2014, 09:38:27 PM »
Here's two that I took for practical reasons, but turned out to pretty good photography, too :)


Now thats funny, creating this thread I was thinking that I should try some macro of my bike wheel hubs, of some chain links and possibly of the cleats mechanism... you've beaten me to that.


...by 6 years ;)

These were actually not shot with a macro, but with a Tamron 28-75 f/2.8 on a 40D. That was an excellent lens with good close focusing ability. Too bad my copy started giving wrong focal lengths in the exif, and poor AF speed most likely due to exposure to humidity on a trip in Africa.

If you're interested, the pics show a venture into 'half step gearing' - a temporary solution I used to modify my roadbike for riding the 'Marmotte' bike ride  in the French Alps. It is normally set up for riding in the Netherlands (flat country), but by combining the 9 speed 11-32 cassette from my mountainbike with a 39t and 42t plus an old Suntour front derailleur that can handle the small step size of the front gears, I ended up having 17 gears of different step size which, despite a complicated shifting pattern, worked like a charm. See http://sheldonbrown.com/gear-theory.html and look for 'Half-Step Gearing'.


Intersting story, I'll check the link for sure. That Sheldon Brown site is a bible for cyclist isn't it. Personally I've been riding a fixed gearfor a few years as I mainly ride around the city and park in crowded bike racks where I've had my derailers bent a few time. Fixies are so much more reliable and give so much feedback when riden with cleats.

I've spent several months in NL in 2011 and it is flat indeed, although the wind can be quite strong along the Ijsselmeer. Needless to say that my Canadian home town now feels so unfriendly to bikers since I've been in NL though.

8
Macro / Re: Mechanicals
« on: July 26, 2014, 09:27:34 PM »
Nice images, keep them coming!

Personally, I also like it when my images show some wear and tear (or gunk)... Although this images from my daily job are not very strong artistically.

those are really neat, what kind of magnification? is that fibreglass or carbon and you analyze the failure points? i know a little bit of metalurgy, enough to know why something is broken, and i find the microscopic level of failure analysis fascinating, although its not really necessary for me to know.

the aluminum scratches experience came from trying to get a clean product shot of some industrial nozzle boxes, i wanted them to look nice to sell, but the reality is they are going in the back of service trucks and we dont bother to keep them pristine. i tried cloning them out but between the grain of the brushed aluminum and the variation in colour from the reflections i made zero progress. i'll see if i can track down an example. (cant find i think its on the work computer)

first a shot i kind of like and keep trying to improve upon, have to get in and get out before the camera gets coolant all over it, the shop is annoyingly dark too. i like this one because i managed to get a wisp of smoke and some motion blur at the same time. shutter speed was a hair too slow because i have camera shake too, but at least theres somewhere for improvement!

second shot is a brass bushing, really fun to take pictures of, the brass just glows under the right light.

It is fibreglass. The first one is about 1:1 and the micrograph is only about 35x taken on a scanning electron microscope.  I have some of up to 5000x, but not with me right now. I do material durability testing and those images are for analyzing failure modes.

I understand that for commercial shots, scratches and gunk are not strong selling points. I guess one really needs to start from a brand new part or rebuff it.

I like your image from the lathe turning the threaded bar and the brass does look good indeed.

9
Macro / Re: Mechanicals
« on: July 25, 2014, 07:32:02 PM »
Here's two that I took for practical reasons, but turned out to pretty good photography, too :)

Now thats funny, creating this thread I was thinking that I should try some macro of my bike wheel hubs, of some chain links and possibly of the cleats mechanism... you've beaten me to that.

10
Nice tip, thanks!

On the negative side, you loose definition in the US flag.

11
Macro / Re: Mechanicals
« on: July 25, 2014, 06:17:22 PM »
Nice images, keep them coming!

Personally, I also like it when my images show some wear and tear (or gunk)... Although this images from my daily job are not very strong artistically.

12
I think they're all good for different images. However, You will probably end up having parts of the airplane in your images with the ultra-wide lens. If the plane is a low wing design, you may only end up having good telephoto opportunity.

Finally, if you know the pilot, try to make sure the windows are going to be clean and that you bring a polarizer to cut through windows reflections.

13
Photography Technique / Re: Black & White
« on: July 25, 2014, 11:41:50 AM »
If you shoot raw and then convert to B&W, you have control over the conversion.

I don't use Photoshop much but if I'm not mistaken, the basic monochrome is just a balanced conversion of all color channels luminance to greyscale and generally results in a low contrast, somewhat unnatural image and you loose color information in the conversion as it turns to 8-bit. I think you can make a B&W conversion in the channel mixer and keep the channels information for optimizing the images, but I've never done it myself.

On the other hand, I think Lightroom converts by weighting each color channel luminance to the same ratio as the sensor, so twice the weight for greens. This results in a somewhat more natural images. You can then use the channel mixer tool to change the effect to taste and the white balance will also influence the conversion. I quite like this tool. The channel mixer works the same way as filtering on B&W film, therefore red darkens foliage and sky, blue lightens the sky and so on. Basically a color filter (or cursor in digital) lightens its component and darkens its complement.

In camera monochrome is likely different for each camera model. It might look good or not and it is jpeg so compressed to 8-bit and won't allow for playing with the channel mixer.

Happy shooting.

14
Macro / Re: Mechanicals
« on: July 25, 2014, 11:09:37 AM »
what i do for a living, and a little experiment with a homemade light box.

This claw is not a macro shot is it?  ;) Anything mechanical goes, no worries... You photograph industrial stuff or you make mechanical stuff for a living?

15
Macro / Re: Mechanicals
« on: July 25, 2014, 11:00:26 AM »
That's a difficult photo to capture, a flash might have ruined it.  Shiny metal is among the most difficult for me.

I would have used a flash to have a bit more lateral light, but I would have used a comparatively large diffuser. The light was an office ceiling neon array so it is very omnidirectional. For this particular shot, I was able to position the assembly so that the light was relatively good. On the other hand, for the non-macro close-up shots of the entire assembly, the diffuse light was harder to make interesting and the images look bland.

Here is another shot. Admittedly, this is a crop from a more general close-up. But I think it also looks good.

Still many thanks for the feedback and tips.

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