January 30, 2015, 08:13:24 PM

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Messages - noisejammer

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1
I just like to have only the eyes in focus in the face, so subject-background-seperation will not help here. From Zeiss I only own the 135 f/2, and I wish to get it tag sharp at least 90% of the time at f/2 without zooming the live view on the camera.
You can easily calculate the distance to the subject by using
D = F * H / h where F = focal length (in your case 135mm), H = subject height or width ( I'll guess 450 mm width) and h = sensor height or width (if you're in portrait orientation it would be 24 mm width. From this, I get your subject distance is going to be about 2500 mm.

Now go to www.dofmaster.com and do your own calculations. I got that the total DoF will be 3.9 cm split nearly equally between front and back. That assumes the circle of confusion is 0.03 mm. If you want the image to be a fair reflection of your lens' capabilities, you can set the CoC at 0.015 mm and you'll find the total depth of field is 1,9 cm. That's 1 cm in front and 1 cm behind. If you're human, you will sway by several mm (as will your model - even if he / she is trying to stand absolutely still.

The result is that even if your focus is perfect, you might only get 50% of your images sharp but you should get about 25% sharp. This is why it's far smarter to stop down the lens a little and make sure you nail every image.

It's easy to test this - focus on something that's difficult to see then shoot off several images. You can even use this to estimate how much you sway which should inform how fast an aperture you should be using.

2
Do you consider the loupe to be good enough to focus on the eyes for a close-up (from top head to including shoulders) portrait at f/2 or do you get better results when you do zoom in (the camera button) on liveview?
Head and shoulders at what focal length? I'll guess 85mm / 1 m.

The worlds great optimist-sage, DofMaster, says at f/2 is 85 mm lens, 1 m -> 2cm ... that's assuming the CoC is 30 microns (which is quite crappy.) You would do better to try for CoC around 15 microns which means the DoF is 1 cm.

To achieve this, you and your subject have to stand still so that neither of you sways by more than 5 mm. I wish you luck - you will need it.

It's not for nothing that pro's shoot portraits at f/4.  If you want more bokeh, separate the subject from the background or use a green screen.

3
Thanx  ;D
Just some small questions:
-How easy is it to see the composition (e.g. the entire screen) with the loupe attached? Can you see the entire screen only by 'hovering' with your eye over the loupe or can you still see your entire screen at once?
I can see the entire screen without having to move my eyeball. Of course, you have to use magnified live view if you really want to nail focus. I frame the image, pick my focus area, focus, zoom out then trip the shutter.
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-What is the purpose of this gorilla plate?
I think it interfaces with the other video-related things Zacuto makes. It may allow some of the parts to glom onto the camera. As I said, it's useless for stills - use the Z-FRM or Z-FRM32.
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-The 2.5x and 3x are different magnifications I assume?
Yes (I assume) - I've not used the 2.5x so I can only go by what's on the Zacuto site.
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I see in some youtube videos that there are some kind of spacers that come with the package to increase the distance between loupe and screen and thus the magnification. These spacers are not related to the 2.5x and 3x versions?
No - the spacers allow for greater dioptre correction. I have never used mine.

NJ

4
I tried the Hoodman before trying a Zacuto. I found the Zacuto to be far, far better.

Zacuto makes three Z-Finder models, the Junior, Pro 2.5x and Pro 3x. I haven't tried the Junior so I can't speak to that. Between the Pro versions, my choice was based on dioptre adjustment. If memory serves, the 2.5x version offered lower magnification but was suited to near-sighted shooters. I'm not near sighted so I chose the 3x version.

The Gorilla plate that comes packaged with some Z-Finders is a waste of space. If you can save some cash by not buying it, I recommend you do.

5
I'll post a dissenting opinion.

I've purchased just about every screen available for the 5D2. I have tried precision matte screens, split focus, the original, microprism and a few others. The prices varied from $15 to $200.

The short version is that none allowed my to achieve critical focus with my Zeiss ZE lenses.

I then tried a Zacuto Z-finder Pro loupe and mounted it to the lcd on a clip-on frame (pn Z-FRM or Z-FRM32 depending on your camera.) I can nail critical focus almost every time. Yes, it's a little unwieldy but the camera is pressed against your eye and it's stable. The second issue is that this goes through batteries, so you need a few in your pocket. It does however work.

6
Post Processing / Re: Is Coma Fixable in Post for Astrophotography?
« on: January 21, 2015, 10:31:24 AM »
Does the point spread function vary across the image? Or does the function completely describe the aberrations across the lens?
Coma is a radial aberration so the psf varies radially. Richardson-Lucy deconvolution was developed to allow correction for this. Since stars are essentially point sources, it's quite easy to determine the psf over the entire field.
If memory serves, it was originally a software kludge that allowed the space telescope to be used while COSTAR was being developed.

7
Post Processing / Re: Is Coma Fixable in Post for Astrophotography?
« on: January 20, 2015, 10:56:42 PM »
Yes, but with some difficulty. I suggest you look at the Richardson-Lucy transform. You will find implementations in MaxIm and AstroArt - perhaps in others too.

8
I use a this ... http://www.thinktankphoto.com/products/streetwalker-harddrive-backpack.aspx . It's more than sufficient for my 1D4 + 5D2, 70-200/2.8, several smaller lenses and a decent sized laptop. You can remove some (or all) of the compartments as needed and there's a waterproof cover that keeps things reasonably dry.

If you're worried that the airline may gripe about the weight of your bag, wear a jacket with multiple pockets. If they get overly fussy, hang your camera around your neck and unload the bag until they let you keep it. Once you're on board the plane, you can reload the bag.

I also subscribe to the idea of taking a sling bag along for my camera except that mine travels empty in my checked luggage.

9
A choice of two, take images and stitch like crazy...

1. Hartblei 80/2.8 super rotator
2. Zeiss ZE or ZF.2 50/2 Makro

Both are superbly sharp and easily out-resolve my 5D2. The Hartblei also offers tilt-shift capability.

10
Lenses / Re: Comparison: Yongnuo 50mm f/1.8 vs Canon 50mm f/1.8
« on: December 29, 2014, 12:59:49 PM »
<p>PetaPixel has posted a comparison between the Canon EF 50mm f/1.8 and the obvious clone the Yongnuo 50mm f/1.8. </p>

These lenses have different optical designs (from the comparison on Petapixel, the YN is clearly better), they have different irises (the YN is better) and they have different price points (again, the YN is better.) Apart from both fitting on the EF mount, I don't see there's any cloning involved at all.

11
Canon General / Re: RTFM. Do you?
« on: December 10, 2014, 05:05:17 PM »
Those who play first, curse later - have you ever tried to set up a 1-series without rtfm... :D

12
Third Party Manufacturers / Re: Most ridiculous camera ever?
« on: October 31, 2014, 05:53:32 PM »
...and people are scared of Magic Lantern brikking their cameras...

Man, I thought the Df was hideous but this really wins the 2013 fugly prize. :)

13
Canon General / Re: seeimpossible.usa.canon.com?
« on: October 07, 2014, 09:16:55 PM »
Oh give me a break! You really can't think that "youtube" comments are representative of anything other than the opinions of the handful of individuals who comment – who, for that matter, could very well be Sony employees for all you know.
At least one of the comments did not come from a Sony employee.
In any case, why would Sony employees see value in getting Canon to make better products?

14
Lenses / Re: Does it matter anymore who makes the sensors?
« on: September 24, 2014, 08:19:20 AM »
No, not the same situation at all. Canon has to compete with Nikon, Sony, and the others. The other companies are what give Canon their incentive to innovate.
Nonsense! Canon's only incentive (like all the others) is maximising shareholder value. Innovation and product improvement are happy side effects of this. Innovation helps when you are trying to attract new customers (which is why there's such a turnover of models at the bottom end of the market.) It may help to secure brand loyalty when customers go from one lens to (say) four. After that, the customer is locked in and you give them the minimum that will prevent them from walking away in disgust.

The slow turnover at the top end is a result of the manufacturers knowing their market - if users find change between models significant, the captive user may upgrade. If not, they will probably sit on their hands and wait for the next model before reconsidering. This is a difficult field to play in. If a disruptive model comes along - say the A7 series - you may suddenly find a number of high end customers changing brands at very low immediate cost.

But the more system unique equipment a photographer owns, especially if expensive, the less likely they will switch to another system....

Of course, the camera manufacturers might not like this freedom.  Locking in customers is a good business practice. You don't make money by making it easy for your customers to go elsewhere.  8)
Yay.... at least one other person gets it!

15
Lenses / Re: Does it matter anymore who makes the sensors?
« on: September 22, 2014, 10:26:48 AM »
Being held to ransom - well that's what contracts are for. So that's nonsense too.
No, it isn't nonsense. If there is only ONE sensor supplier, then you either pay what the supplier wants or you don't get their sensor, then you have no product. It would in reality simply raise prices for the end user.
Contracts end and have to be re-negotiated, companies sell off divisions, the buying companies may and very often do have a very different vision, it’s not nonsense. ‘Ransom’ isn't exactly the best word though.
Of course contracts can end and they can be re-negotiated. On the other hand, they can be set up to protect both parties. For example, an option can be sold on a specified product to be delivered at a specified price on a specified date and with a specified performance. You can agree to terms that will be acceptable if either party cannot fulfill their part of the deal. The important part about contracts is you can't break the laws of physics and you can't break the laws of of a country. Everything else can be negotiable.
 
Competition makes everyone better and can only benefit consumers. There are always better ideas and our money helps move technology forward.
I'm not convinced this is either true or applicable. It certainly works when the item or service is fungible but it's complete bs if one source has access to technology that excludes the others from catching up. It's also bs if circumstances prevent the customer from changing supplier.

The camera market finds both circumstances. Firstly, technology is heavily protected through patent law and second, users cannot migrate because their lens "investment" constrains them to using a single source for camera bodies. Now, if third parties - say Sony - would start offering EF or F.2 mount cameras, everything really could change.

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