Cotton. Sidney Cotton.

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"He caused a lot of trouble over here, you know."  A librarian at the Royal Aeronautical Society, when asked for references on Sydney Cotton.

It's been a while since I did a history article. I love writing about the true "characters" of photography, and to be honest, I hadn't stumbled across anyone that really interested me for a while. But while I was writing an article about the most decorated photoreconnaissance flight in history, I kept running across the name Sydney Cotton, who was considered the father of aerial reconnaissance. Continue reading

A Thinner Sensor Stack

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A few months ago, before my hiatus from blogging, we did a series of articles showing the effect that a thick sensor stack (the glass above the sensor) had when we use adapted lenses designed for a thin sensor stack. The first one was mostly about theory, the second about when it was likely to actually be noticeable, and the third gave a general summary of when you might expect problems. All of that theory and prediction is good and useful.

The articles generated a fair amount of discussion about removing filter stacks on cameras so that they would perform better with legacy or film lenses designed for little or no sensor stack. In theory, that would make a big difference, but changing the stack has its own set of issues: focus is changed, infrared filtering can become inadequate, etc. Recently, though, our friends at Kolarivision, who had contributed a lot to our database on filter stack thickness, asked us to do some independent resolution testing for them.

They had modified some Sony a7R cameras, removing most of the thick sensor stack and replacing it with thinner Schott BG39 glass (I do not know the exact thickness of the replacement glass, but it is described as 'significantly thinner'). The replacement glass closely matched the original IR transmission, maintaining accurate colors, but, in theory at least, should improve resolution on wide-angle, wide-aperture, short-backfocus distance lenses. In other words, it should improve the performance of the a7R using wide-angle Leica and other M-mount lenses designed for film.   Continue reading

A Brief 400mm Comparison

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Canon shooters have a bit of 400mm excitement right now. The biggest news, of course, is the release of the 100-400mm f/4.5-5.6 IS II lens, replacing the original version that's had a very long, successful run. Not quite so much excitement was generated by the release of the 400mm f/4 DO IS II lens. It too replaces a long running lens, but one that has been considered more of a niche lens. (I'll admit, though, it's been one of my favorite niches. I used the 400 DO a lot over the years.)

Most surprisingly, neither lens was released at a huge price increase. The new DO II lists for $6900, compared to $6470 for the original version. The new 100-400 IS lists at $2200 compared to $1700 for the original. Both new versions promise several improvements to the older versions, but we were most interested in how good the optics might be. So, of course, we ran these through Imatest at 400mm the day they came in.

One thing I need everyone to be aware of: We tested these on the new, high-resolution film-transparency, backlit Imatest targets. These are particularly good for testing high-resolution telephoto lenses, but do give us higher resolution numbers than the larger, printed charts we use for more general testing. So, while you can compare the results of these four lenses today against each other, you can't compare them to some older Imatest numbers for, say, the 70-200 f/2.8 lens and draw any reasonable conclusions.

We're simply evaluating them today to see if the newer optics provide a higher resolution than the older ones. Of course, we expect them to, but it's still worth checking. The original versions of both lenses were pretty darn good.

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Christmas Special - Save 25% on Rentals

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Do your holiday plans or New Year's resolutions involve photography?  If you've been excitedly waiting to use a certain piece of gear, now is the best time to try something for the first time.  Use promo code HOLIDAYS to save 25% off any rental this season from December 23rd to January 2nd.

  • Orders must have a delivery date between 12/23/14-1/2/15
  • Can not be combined with any other offers
  • Limit- 2 rental orders per person

One, Single Samsung NX-1 Test

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I just want to be clear, before we get started, this is not an NX-1 review. It's not even a complete optical test. It's simply me answering a single question: is this new Samsung worth further investigation from an optics/image quality standpoint?

Samsung's 28.2 megapixel, APS-C backlit sensor should capture more light with less noise, with a bit higher resolution than the 24 megapixel sensors in the competition. The hybrid AF system with striped illuminator should be quick and accurate. The short lag time 2.36 mpix OLED, low-lag-time EVF should be great. I know the built-in WiFi will actually be useful, because I've used lesser Samsung cameras in the past just for that feature.

All of those things are well and good. But none of them are even worth investigating until one simple question is answered: is this camera system (meaing camera and lenses) competitive with other APS-C cameras I can buy? Because I've sung the "Baby, I Love Your Sensor, but you Just Ain't Got No Optics Blues" to too many cameras already. Continue reading

Get 5% Back On Keeper Purchases

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Looking to buy some gear this holiday season but not sure what? Try it, then buy it with Lensrentals Keeper. During the holiday season, we're adding an extra bonus! Get 5% of your Keeper purchase price back as a rental credit, good towards a future rental.

The Details

  • Any Keeper purchase from 12/1/14 - 1/31/15 is eligible
  • 5% of purchase price, net of sales tax
  • Rental credit will be applied to purchaser's account on 2/1/15

Black Friday Sale

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It's time for our 5th annual Black Friday Sale! The sale begins at 8:30 AM CT on Wednesday.  At our sister site, LensAuthority.com, we'll be giving you 10% off all used equipment. We'll also be having special deals throughout the sale, so keep your eyes peeled on the Special Deals section and be sure to follow LensAuthority on Facebook and Twitter to get announcements of any special deals during the sale period.

Over at Lensrentals.com, we're giving you are best discounts of the entire year! Place an order for any arrival date before April 1st, 2015, and get 25% off using the promo code BLACKFRIDAY. Been longing to try a certain lens? This is the perfect time to take it for a test drive (and don't forget about our Keeper program when you fall in love with it).

The Details

  • 25% off any rental placed at Lensrentals.com using the code BLACKFRIDAY
  • Order must be placed between 8:30 AM CT on 11/26/14 and 11:59 PM CT on 12/1/14
  • Eligible for any rental with an arrival date before 4/1/15
  • Limit - 2 rental orders per person
  • Not combinable with any other promotions or coupons

Cracking Open the 7D II

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OK, I have to admit I really like the 7D Mark II. I didn't want to because it wasn't what I wanted. I wanted to see the new Canon chip foundry that would be cranking out high-resolution sensors. But despite wanting to hate the 22-megapixel APS-C camera, after a fairly short exposure to the autofocus system, I have to admit I like it. There's just something about getting every shot in focus every time that's appealing to me.

However, when I read that Canon claimed the 7D II has "4 times better weather sealing than the original 7D" I went mildly nuts. Most of you know I hate marketing drivel. HATE IT. Most of you know I'm generally not impressed with weather sealing claims. Unless something has changed in the last 30 seconds, weather sealing still means, "the warranty doesn't cover water damage."

So when I read the claim "4 times more weather sealing" my inner cynic just thought 4 times zero equals zero. But I wanted to be fair so I decided I'd open up the 7D II before I wrote a scathing article about making ridiculous weather sealing claims. Which results in me once again writing an article where I have to admit my assumptions were wrong less correct than I would have liked. (Sorry, I forgot for a moment this was the internet where no one ever says "I was wrong.")


The 7D and 7D Mk II looking awfully similar in front view.


For those who want to take my word for it and skip on to some other blog, the Canon 7D Mk II may be the best weather-sealed camera I've run across. It's excellent. For those who would rather see for themselves, gory camera dissection pictures follow!!

I'll add, because someone always wants to comment about the poor quality of my dissection photos, that you're welcome to try shooting with one hand while taking two cameras apart with the other hand under 4 tungsten hot-lights, making sure you have the camera back together by the end of your lunch break. We don't do high-quality product photos back in the repair department. But better this way than if we let the product photo people try to take the cameras apart.

Continue reading

About That 25-300mm f/2.8 You Wanted

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I get an email or text about once a month asking me if I think Canon, Nikon, or some other photo manufacturer will ever make something like a 24-300mm f/2.8 zoom lens. I'm usually gentle with those people, because I realize that a lot of people truly believe that if they want something badly enough, someone could make it for them. Occasionally, someone exhibits the Dunning-Kruger Effect and tells me that they know it's a plot on the part of the manufacturers to make us buy multiple lenses instead of just one that could do everything.

I had another one of those emails a few days ago, so I thought it might be interesting to show everyone what a 25-300mm f/2.8 would (approximately) look like. We don't actually have a photo lens of that specification, but our video friends do: The Fujinon 25-300mm T3.5. (For those who don't know, f is a calculated value, T is actual light transmission. Most f/2.8 lenses are T3.5 to T3.8.)

The Fujinon is a PL mount lens, so I'm afraid you won't be able to adapt it to your 5DIII or D810. If you really want to, though, you could buy a PL modified Canon 7D camera and use this as your walk-around lens.

Continue reading

Quick Zeiss 85mm Otus MTF Charts

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Well, we finally got a few copies of Zeiss' newest Big Ass Lens, the 85mm f/1.4 Otus in Friday afternoon. I didn't have time to do a whole lot with them other than take a few shots, and run them through the optical bench for MTF testing, so this will be a short post. (Assuming I get a little more time with them Monday before they ship out, I'll add field curvature graphs as an addendum to this post.)

The summary is short and sweet: the Otus is every bit as good as it's supposed to be, and the best 85mm f/1.4 lens we've tested. At $4,600 and 2.5 pounds of manual focus lens, we sort of expected it to be the best 85mm f/1.4 we'd ever tested. But still, life does like to chew up some tasty expectations and leave a pile of disappointment in the front yard sometimes. So it was nice to see the Otus 85 was as good as advertised.


MTF curves for 5 copies of the Zeiss 85mm Otus compared to the standard ZE 85mm f/1.4


I put the original ZE 85mm f/1.4 MTF charts up for comparison, since it's a nice middle-of-the-road 85mm f/1.4. You can make some more comparisons from our last article on 85mm lenses in general. And yes, I'm looking forward to seeing how the Sigma 85mm f/1.4 Art stacks up against the new Otus.

The quick summary is this is an amazing performance. Notice that the Otus at 50 line pairs / mm (orange lines) is about as good as the original ZE 85 is at 30 line pairs / mm. That really is amazing. But the performance difference is there at every frequency and at every spot across the lens field. If you want the sharpest 85mm money can buy, well, you have to buy the most expensive 85mm money can pay for.

We also checked variance on these copies. Again, I'll use the ZE version for comparison since it's a lens with very good variance numbers. As one would expect for this price, the Otus is even better than the ZE 85mm, meaning the difference between best and worst corner on the average Otus 85mm is quite small -- too small to detect in a photograph or even with some pixel-peeping.

I'd love to have some profound conclusion here. But like the 55mm Otus, what we expected is exactly what we got: a very expensive, very large lens that is the best lens available optically in this focal length.

Addenedum: Field Curvature

The Otus field curvatures are really remarkable, both tangential and sagittal are nearly perfectly flat. Below are the field curvature graphs wide-open at 30 line pairs / mm. The flattest we've seen so far on any lens.

Roger Cicala


October, 2014