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 1 
 on: March 03, 2015, 10:53:57 PM 
Started by Qwagmire - Last post by Bob Atkins
Well, I have a 70D and a 6D and both are truly excellent cameras. I like the articulated LCD of the 70D and the touch sensitive screen, despite the fact that I've never really liked the idea of a touch screen. Turns out it's much easier to use in low light than the buttons and wheels and probably faster too. The 6D excels in image quality and the low light AF with the center zone is amazing.  It's also almost 6oz lighter than the 7D MkII. I don't have a 7D MkII (though I do have the 7D MkI) but from what I've read and a brief time handling one it looks like an amazing camera with the best AF system of any EOS and good low light ability.

I'd say that if you can only have one camera, I'd go for the 7D MkII especially if you want the best AF performance and it's in your price range. It does more things well than either the 6D or the 70D, though the 6D and 70D have some features that the 7D MkII lacks (but which you may not need or care about). The 6D has GPS built -  in for example and the 70D has the articulating screen.

Right now there are some really really good deals. You can get...

An EOS 6D + Pro-100 printer for $1299 after a $300 instant rebate and a $250 mail-in rebate. It's cheaper with the printer and the extra $250 mail in rebate than if you just  buy the body alone! http://www.adorama.com/ICA6DZ.html?kbid=12417

An EOS 70D + Pro-100 printer for $899 after rebates ($200 instant + $250 mail-in). Again it's cheaper ($100 less) with the printer than without it. http://www.adorama.com/Refby.tpl?refby=rflAID012417&sku=ICA70DZ

An EOS 7D MkII for $1699. With the following link you also get a 32GB memory card, a remote release, a holster case, a cleaning kit and a (not very useful but it's free) table top tripod. http://www.adorama.com/Refby.tpl?refby=rflAID012417&sku=ICA7DM2A

The 70D is the best bargain, the 7D MkII is the best all around camera and the 6D will give you the best ultimate image quality as long as you don't need high speed AF tracking, high speed continuous shooting and the 1.6x "lens multiplier" to extend telephoto reach.

The mail-in rebate info is here - http://www.adorama.com/pdfs/rebates/Canon_MIR_claim_form_28MAR2015.pdf

 2 
 on: March 03, 2015, 08:24:23 PM 
Started by Qwagmire - Last post by Qwagmire
I had a 5DIII and loved it, but it was a lot of camera to carry or sit in the closet.  Im coming back but on a tighter budget and have been looking at 3 cameras:  The 7D2, 6D, and 70D.

I like taking nature/wildlife/museum (low light) pictures, my kids playing, occasional birding, with occasional sports (golf, car racing, etc)

I like the 6D because of the low light qualities.  We go to a lot of museums and in the past the 1D2N and 5D3 did well enough in the low light, but I always ended up with some darker pictures. 

The 7D2 looks like it would be better for my "sports" adventures, but I would lose some of the low light.

The 70D looks like similar enough to the 7D2 that I wont lose much and can grab a few lenses for the price difference.

Any thoughts out there?  At this point I'm leaning toward the 7D2, with the 70D and 6D following closely.   Or maybe the 70D/7D2/6D. 

Thanks for your thoughts!

 3 
 on: February 27, 2015, 04:32:01 PM 
Started by Frank Kolwicz - Last post by Frank Kolwicz
OK, now we're really off into the stratosphere! To the moon, even.

I know you've made the point about having lots of disturbed air between the lens and subject before and it makes a lot of sense, but do you really photograph subjects as small as the largest birds at distances of several hundred yards (meters) and expect exhibition grade images?

And, of course the moon is tough to photograph *through MILES of atmosphere*.

This is way off course from my initial message about the effect of camera temperature on microfocus adjustment settings which has nothing to do with thermal cells inside large, almost completely empty reflector telescopes; the heat pouring out of a car with the heater on in winter and shooting through huge expanses of atmosphere.

Regarding those hollow reflectors: if the internal air circulation is such a problem, why not partially evacuate them? Industry makes huge mirrors, they can make large pieces of glass to seal the front, like photographic reflector lenses have. Caulk-up all the mounting fasteners and around the eyepiece, attach a little hand or foot operated bellows to suck some of the air out just before a shot and there you go! Of course it wouldn't be quite that easy, the pressure of the evacuated interior will distort the whole structure, but that's just a design element that needs to be addressed in the planning stage.

A 50mm lens would certainly be better, but at 10 meters? For sparrows? I don't have the field skills or physical ability to photograph any kind of birds that way, I'd like to see *your* images. And, also regarding distances to subjects, I think in terms of feet up to about 200, or so, and then forget it! Beyond that range even large hawks are in the "record shot" category, not to be confused with high-quality images. Even birds as big as Great Blue Herons only become part of a landscape at distances in that range and beyond.

 4 
 on: February 27, 2015, 01:03:36 PM 
Started by Frank Kolwicz - Last post by Bob Atkins
Overstating? Maybe, though I have certainly seem the effect a number of times when shooting at focal lengths over 500mm. I remember if being quite noticeable when shooting from a car with the heater on in winter. It's also quite noticeable on shots of the moon, where even when using a fixed manual focus setting, you can see variations in sharpness from shot to shot due to atmospheric turbulence.

It's not an effect I'd typically worry about under normal shooting conditions where the subject is reasonably close. However for long distance shots atmospheric turbulance sets a real limit on image sharpness. It's hard to say what the distance is where you start to notice it, but it's certainly less than a few hundred yards when conditions are bad, and it's just about always there on terrestrial shots of a mile or more. It's one reason why longer and longer lenses become less and less effective for high magnification shots at long distances. Even with a perfect lens and neglecting things like size, weight , cost, tripod stability etc, a 500mm at 100m will give you better results than a 5000mm lens would at 1000m. A 50mm lens at 10m might be even better!

I think the point is that when you have a perfect lens and perfect focus and a perfectly stable tripod, there can still be effects that will lower image sharpness due to temperature and turbulence. There are nights that amateur astronomers might as well stay indoors because "seeing" is so bad. Professional telescopes are put on the top of high mountains to try to get above as much of the atmosphere as possible and so reduce image degradation.

Can't really comment on the difference between black and white lenses, though I do remember a test that Popular photography did many, many years ago when they found that black lenses/cameras were indeed quite a lot hotter then white lenses.cameras in direct sunlight. White cameras never really caught on (Minolta once made one). It wasn't a small effect either, maybe 30 degrees difference, though I don't know the exact conditions. Could have been noon in Death Valley...though more likely it was done in New York.

 5 
 on: February 27, 2015, 10:02:43 AM 
Started by Frank Kolwicz - Last post by Frank Kolwicz
Hmmmm, makes me wonder how I ever managed to get critically sharp images!

But, then I remember that I never had a serious problem with a properly functioning 600mm lens. I expected to get 90+% sharp images with a cooperative subject and a decent amount of light and almost all from my car in recent years. All of my problems with soft images have been due to a poor lens or with low light and active subjects.

Also, I would think from your description that the worst possible condition would be with the lens in full sun when it would heat up dramatically above ambient air temperature and send shimmering waves of heat right off the front of the lens hood in addition to the internal  convection cells. And how about those big black Nikon lenses? Heat must really wreck their performance.

Aren't you overstating this a bit?

 6 
 on: February 22, 2015, 10:29:30 PM 
Started by Frank Kolwicz - Last post by Bob Atkins
If you shoot from a warm car into cold air you'll get a lot of turbulent air flow. The hot air will flow out of the car and in front of the lens. This is a separate effect from focus shift, but one which will soften images significantly.

To get the optimum optical quality, the lens needs to be at the same temperature as the air. Normally people just ignore this, but it's a very well known phenomenon to amateur astronomers. Some telescopes can take hours to equilibrate and they won't perform well until they do. There's absolutely no way to observe with ultimate resolution with a telescope from a heated observatory and I'd guess the same is true for photography form a car that's not at the same temperature as the outside and with a lens that's not thermally equilibrated.

The air inside the lens also needs to be at a uniform temperature or optical quality will again suffer due to convection cells being setup. Longer lenses with larger internal volumes are most affected.

http://www.lcas-astronomy.org/articles/display.php?filename=temperature_changes_and_optics&category=general
http://www.telescope-optics.net/turbulence_error.htm

Temperature causes a focus shift with long lenses. This is well known and the reason what most telephoto lenses will focus "beyond infinity" to allow for the effects on focus of temperature. The focal length of the lens will change slightly. It's not surprising that this might upset AF and AF microadjustment since phase shift AF is a "drive to" process, not a feedback process. Live View is a feedback process, even with assistance from dual phase sensitive pixels, hence it will typically get better (but slower) AF accuracy then the normal reflex phase shift AF system.

You can easily see these effects if you can put an eyepiece on a long lens and use it as a telescope at high power. Images that otherwise look stable in the viewfinder of in Live View can be seen to be shimmering and shaking as thermal air currents both inside and outside the lens distort the view.

The effect is shown in the video near the bottom of this page - http://www.bobatkins.com/photography/tutorials/astrophotography.html


 7 
 on: February 22, 2015, 03:09:57 PM 
Started by Frank Kolwicz - Last post by Frank Kolwicz
As Roger Clark shows at the end of the article at http://www.clarkvision.com/articles/microadjustment/index.html, microfocus adjustment varies with camera internal temperature.

I had this in the back of my mind for some months, but didn't put the information to use until today. Here in western Oregon, the winter weather usually doesn't vary much in temperature during the course of a few hours or a day, protected as we usuall are by a nice thermally insulating cloud layer much of the time: there are days when the variation from max to min is less than 5 F. In the last month or so we've been in an uncharacteristically sunny spell and I do essentially all of my bird photography from my car, so the interior is heating up more than usual and I now have to adjust the microfocus periodically during the day or I will get runs of images that are out of focus with a Canon 7dii and EF600/4LISii plus 1.4x teleconverter (effective focal length about 1300mm).

I probably have run into this problem before with some of my other long lenses over the years, but, since my photo gear is stored in my car in an unheated garage and I use little heat in the car for comfort and have the window(s) open for long periods when I'm actually working on a bird, the ambient temperature doesn't vary that much in winter and I never gave it any thought.

All of a sudden my car has now gets a lot warmer than the outside air as the morning progresses and the camera is also getting warmer and I'm getting lousy focus! I had previously adjusted the microfocus to a level of -1 or -2, but today I had to go to -5 to get things back to acceptable focus by 10AM.

Clark's graph shows a 7 unit change in the adjustment for 45 deg F change in camera temperature and slightly less ambient temperature change.

Note that this does not apply to using LiveView, since it is reading directly off the sensor no matter what the temperature is, but I often switch between the two methods and now have to be concerned that the excess sensor heating caused by using LiveView for any length of time will disrupt the focus adjustment when switching to phase-detect AF via the viewfinder.

I guess I'll have to learn to use Clark's quick AF microadjustment technique after all.

 8 
 on: February 16, 2015, 10:03:52 PM 
Started by klindup - Last post by Bob Atkins
If you wanted two of them it would be cheaper to fly to New York and buy them in person (add 8.875% sales tax in NYC).  I think the lowest cost London-New York round trip is about $600 right now.

I guess by the time you add on shipping, import duty, brokerage fees and VAT, just getting one sent from the US probably doesn't save you all that much. Adorama will ship to the UK, but the buyer has to deal with all the additional costs.


 9 
 on: February 16, 2015, 09:58:40 PM 
Started by klindup - Last post by Bob Atkins
Most of what is known about the Digic processors probably comes from the reverse engineering of the Canon firmware by the CHDK and MagicLantern groups. That's all open source. Chipworks has done some reverse engineering the hardware but if you want the details it will cost you a lot of money!

From chipworks - "Canon DIGIC III Image Processor (CK4-1107) - Functional Analysis Report  FAR-0609-803 - USD 16,500.00"   

Here are a few links

http://magiclantern.wikia.com/wiki/Register_Map

https://chipworks.secure.force.com/catalog/ProductDetails?sku=CAN-CH4-6501&viewState=DetailView&cartID=&g=&parentCategory=&navigationStr=CatalogSearchInc&searchText=canon%20digic

https://chipworks.secure.force.com/catalog/ProductDetails?sku=CAN-CK4-1107&viewState=DetailView&cartID=&g=&parentCategory=&navigationStr=CatalogSearchInc&searchText=canon%20digic

 10 
 on: February 16, 2015, 10:56:12 AM 
Started by klindup - Last post by klindup
I can understand why Canon would keep their architecture secret. RISC processors are by their very nature faster than the older conventional architectures with a larger instruction set.  I guess that designing a processor designed to one job leads to more efficiency than a general purpose processor.
Ken

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