August 22, 2014, 02:23:24 AM

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Topics - faustino

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Lenses / cheap AF-S 55-250 STM sharper than L series AF 70-300 USM
« on: March 01, 2014, 11:27:11 AM »
It seems, from the eyes of a 18 megapixel crop sensor, that cheap lenses designed for crop sensor are sharper than L series lenses designed for full frame cameras; I am getting to such a conclusion looking a the comparison from the link below:

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=856&Camera=736&Sample=0&FLI=4&API=1&LensComp=738&CameraComp=736&SampleComp=0&FLIComp=3&APIComp=2

I understand there are other lens characteristics beside sharpness; in this specific case, on vignetting and distortion fields, the full frame lens wins hands down. Without mentioning flare, transmission, and the focus motor. If the plastic lens has a motor that can focus, in proportion, the USM lens has a motor that could move a truck.

Anyhow, it seems that to a crop sensor body, I would better couple an sf-s lens, rather than the full frame lens I already own. I would both reduce my bag weight, and get "better" image quality (somewhat).

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Often I read about the fact that Canon is not innovating their cameras, despite Canon being listed among the most innovating companies out there.

From such readings, I start wandering about how could Canon actually improve the EOS line, and would like to ask your opinion. What would you suggest to change, especially in EOS pro bodies (and maybe pro lenses)?

I am asking the question mainly for curiosity, and also because I have my own wish list of new features, twists and new products; maybe you can explain why my personal wishes actually won’t work.

The changes I would love to be implemented are, for instance:

1. Firmware changes (low implementation cost):
I would like a mode where I could set Aperture and Time - essentially a manual mode, and, instead of ISO, I would like to set exposure compensation; the camera should be able to set automatically the ISO in order to over or under expose according to my setting.
In such a special mode, I would change Aperture with the main dial, Time with the main dial keeping pressed the SET button on the rear dial, and exposure compensation with the rear dial (permutation of functions may be also possible).

2. Physical changes (medium implementation cost):
From the 5d line, I would disintegrate the mode dial. I would change modes by keeping pressed a button while turning the dial. I would also display the mode in the viewfinder (I know I am asking too much here, mode visible in the viewfinder is a feature differentiating the 1 series).

3. New product (high implementation cost and risky):
I would make a special version of one pro body and some selected lenses: I would use structural aerospace grade carbon fiber composites (impregnated fiber or pre-preg) for lenses and camera body chassis. The internal optical formula and the electronics would remain the same, as in the “low cost” version. We would have a 600mm f4 “low cost” at 10k€, and a 600mm f4 CFC at ??k€. I am sure Nasa would seriously give a hard look at such gears for their next shipment to the ISS. I know some who would buy a 10k€ 1dxCarbon and a 20k€ 600mmf4Carbon.
What do you think? Is really Canon not innovating enough?

Thanks!

3
Many people claim that cropped sensors are actually better than full frame and larger sensors for macro applications.
Here is an example:
http://www.43rumors.com/micro-four-thirds-and-macro-photography-by-eugene-kitsios/

Their argument is that for macro photography DoF is the limiting factor. They say that to get the same DoF, the larger the sensor, the smaller the aperture needs to be, which would offsett the light gathering capacity of larger sensors.

As an example, if we compare full frame vs. 4/3 sensors:
- full frame is roughly four times larger than 4/3 (measuring the surface), thus has virtually a two stop advantage in terms of light gathering capacity;
- anyhow, if with four thirds sensor we need to close the aperture to f/8, then on a full frame sensor we would need to close the aperture at f16 to get the same DoF, thus loosing two stop of light (offsetting completely the larger sensor advantage).
I am not sure if the second point is correct. The comparison shall be done considering different lenses on the two systems:
- if we use a 50mm macro on the 4/3 sensor, for correct comparison (to get the same angle of view), a 100mm lens should be used on the full frame (I know there would be slight differences in the final image due to the different aspect ratio).

I am skeptical about the above argument, anyhow I am unable to tell why it would be wrong.
What do you think, is really a crop sensor better than full frame for macro photography? Or is the full frame better? In the latter case, can you explain why?

Thanks!
Fausto

4
I going to buy a new lens, a Canon EF 500mm f/4L IS II USM, and I am struggling at finding a store in Europe that I can trust.

There are some stores that sells at a significantly reduced price that the average. Obviously, I prefer lower prices.

Anyhow, I have a doubt: it may be that the distribution channel, or even directly Canon, selects lower performing copies and sells them through less expensive stores; while better performing lenses are sold through more expensive stores.

Lens performance variability is there and can be easily measured by Canon. For low cost lenses, such additional work (select and send to different stores) would not make sense, but it could make sense for expensive items.

I would like to know your thoughts. Is my idea plausible, or is it completely crazy?

Thanks in advance for your answers!
Fausto


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Lenses / 50 1.2L back-focuses with lateral focus points
« on: May 05, 2013, 04:33:33 PM »
I am experiencing a strange issue with my 50mm f1.2L lens:
when I use any of the lateral focus points (from a 5dmk3), also the cross type, the lens back-focuses. It happens also when the aperture is set to 1.2. When I choose a central focus point, the focus is perfect.

It is not an issue of the camera as I don't see the same problem with the 85mm f1.2L.

I am wandering if this issue affects only my copy or is it normal; maybe it is due to the same spherical aberration that causes the well known focus shift issue (backfocus when stopped down).

Do you have the same issue with your 50 1.2L lenses?

Thanks for your replies (and sorry for my imperfect English)!
Fausto
 

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