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Pentax FA 43Lim/1.9 vs. Pentax FA 50/1.4
An inexact test

The two lenses differ in price and design significantly. The 43Lim is very stylish and convenient. Still, the question remains — is it worth paying extra money for it? Can 43Lim produce better images? If so, how can we see the difference?

Before buying the 50mm prime lens from Pentax, I searched the web for any comparative pictures. Unfortunately, I did not succeed in that. Now that I got a few test images, I would like to share my visual information with you. I hope it will help you to make the right decision.

When comparing the pictures please take into account the following.

1. You may think the images are blurry a little. However, I did not fail to focus the lenses properly, and the exposure was short enough to cope with possible camera movements. The pictures are not perfectly sharp, because I decided to show you actual scans. No computer tricks were applied to them.

Moreover, I believe it is not very interesting to analyze the sharpness of these two lenses. Of course, both of them are perfectly sharp. I wanted to draw your attention to other factors. Many owners of 43Lims claim their lenses produce wonderful colors, marvelous tone plasticity, and unbelievable bokeh. Please pay your attention to such things first.

If sharpness is the crucial issue, please look for other sources of information.

2. Please do not forget that the lenses have different focal lengths. Thus, their DOF and ability to blur the background is also different. According to the traditional theory, the infinitely far point is rendered as the spot with the diameter of (f M)/N, where f stands for the focal length, М for magnification, and N for F-number. Thus, if the magnification and aperture are constant, the degree of fuzziness is proportional to f.

Note: If you know the approach of Harold Merklinger, you may not agree with me. Still I insist that Merklinger's method does not work well in all cases. It is better to use the conventional theory. If you want to learn more about my arguments, please read my artile entitled "Understanding physical meaning of sharpness. Is Harold Merklinger's theory correct?"

3. Is it good to compare lenses of different focal lengths? I think the answer to this should be 'yes'. If we know all the conditions and terms of the test, then we can derive some useful information. Why not?

The subject and the photographer's goal determine everything. Suppose you want to make a half-length portrait of a man under the given circumstances. Whatever instruments you are going to use, two different portraits can be compared with each other. I mean they can be compared from an aesthetic point of view. Technically, they will be different. But I do not care about it. Personnaly, I prefer to look at two pictures rather than analyzing boring MTF charts and other technical data.

4. The scans were obtained @2820 dpi. Thus, fragments at 50% (100%) magnification can be considered as parts of the equivalent print 3 x 4 ft (6 x 8 ft).


Quick portrait

43Lim @4.0; Agfa Vista 200

50/1.4 @4.0; Agfa Vista 200

50% fragments of the scans
43Lim — 50/1.4


Two fuzzy impressions

@2.8; Agfa Vista 200
43Lim — 50/1.4

100% fragments of the scans
43Lim — 50/1.4


Sorry, you will not find any real conclusions here. I am not going to thrust my opinion on you. Nobody but you can decide which lens is the best performer.

By the way, if you think prints are more informative, I have to tell you that it depends. I received a number of different prints from different labs. My conclusion is that printing hides differences.

If you are still uncertain about what to buy, I recommend either of the lenses. Both of them are perfect. Good luck. Have fun.



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